Std - Technical Product Specification 142d35
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The Essential Guide to Technical Product Specification: Engineering Drawing
Colin Simmons and Neil Phelps
First published in the UK in 2009 by BSI 389 Chiswick High Road London W4 4AL
© British Standards Institution 2009 All rights reserved. Except as permitted under the Copyright, Designs and Patents Act 1988, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means – electronic, photocopying, recording or otherwise – without prior permission in writing from the publisher. Whilst every care has been taken in developing and compiling this publication, BSI accepts no liability for any loss or damage caused, arising directly or indirectly in connection with reliance on its contents except to the extent that such liability may not be excluded in law. While every effort has been made to trace all copyright holders, anyone claiming copyright should get in touch with the BSI at the above address. BSI has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this book, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. The right of Colin Simmons and Neil Phelps to be identified as the authors of this Work has been asserted by them in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988.
Typeset in Optima and Gill Sans by Monolith – http://www.monolith.uk.com Printed in Great Britain by Berforts Group, Stevenage
British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 978 0 580 62673 9
v
Contents Introduction Dimensioning and tolerancing of size 1.1 Introduction 1.2 General principles 1.3 Types of dimension 1.4 Dimensioning conventions 1.5 Arrangement of dimensions 1.6 Methods for dimensioning common features 1.7 Dimensioning screw threads and threaded parts 1.8 Dimensioning chamfers and countersinks 1.9 Equally spaced repeated features 1.10 Dimensioning of curved profiles 1.11 Dimensioning of keyways 1.12 Tolerancing 1.13 Interpretations of limits of size for a feature-of-size 1.14 Datum surfaces and functional requirements 1.15 Relevant standards Geometric tolerancing datums and datum systems 2.1 Introduction 2.2 and definitions 2.3 Basic concepts 2.4 Symbols 2.5 Tolerance frame 2.6 Toleranced features 2.7 Tolerance zones 2.8 Datums and datum systems 2.9 Supplementary indications 2.10 Examples of geometrical tolerancing 2.11 Relevant standards Graphical symbols for the indication of surface texture 3.1 Introduction 3.2 The basic graphical symbol 3.3 Expanded graphical symbols 3.4 Mandatory positions for the indication of surface texture requirements 3.5 Surface texture parameters 3.6 Indication of special surface texture characteristics 3.7 Indications on drawings 3.8 Relevant standards
vii 1 1 1 2 3 4 9 12 13 14 16 17 18 19 21 21 23 23 23 26 27 29 29 32 37 45 64 114 115 115 115 115 116 117 118 120 123
vi
The Essential Guide to Technical Product Specification: Engineering Drawing
Welding, brazed and soldered ts – Symbolic representation 4.1 Introduction 4.2 Relevant standards Limits and fits 5.1 Introduction 5.2 Selected ISO fits – Hole basis 5.3 Selected ISO fits – Shaft basis 5.4 Methods of specifying required fits 5.5 Relevant standards Metric screw threads 6.1 Introduction 6.2 Thread designation 6.3 Relevant standards Illustrated index to BS 8888 Normative references
125 125 133 135 135 135 138 140 140 141 141 141 168 169 169
vii
Introduction This guide has been produced as a companion to BS 8888, presenting up-to-date information based on the technical product specification aspects of BS 8888 and the essential standards it references. Its aim is to offer straightforward guidance together with pictorial representations, to all practitioners of technical product specification, i.e. those currently using BS 8888 and those who, in a bid to conform to global ISO practices, are making or wish to make, the transition from the old BS 308 to BS 8888. Its scope is to provide the necessary tools to enable engineers engaged in design specification, manufacturing and verification with the essential basic information required for specifying a product or component. It includes comprehensive sections extracted from and referenced to international standards relating to linear, geometric and surface texture dimensioning and tolerancing, together with the practice of welding symbology, limits and fits and thread data. It also includes an illustrated index to all standards referenced in BS 8888. This guide does not replace BS 8888 which is the definitive standard for technical product realization. Any element of BS 8888 not included in this guide should not be considered as less important to technical specification than those included. Most of the drawings in this guide have been extracted (and adapted) from the following BSI publications: BS EN ISO 1101, BS EN ISO 1302, BS ISO 5459, BS 8888 and PP 8888, Parts 1 and 2.
1
Chapter 1 Dimensioning and tolerancing of size 1.1 Introduction Dimensioning is the process of applying measurements to a technical drawing. It is crucial to the whole process by which the designer will communicate the information required for the manufacture and verification of products.
1.2 General principles Dimensions shall be applied to the drawing accurately, clearly and unambiguously. The following points shall be regarded as general dimensioning principles to be applied to all technical drawings. • • • • •
• • •
• • • •
Each dimension necessary for the definition of the finished product shall be shown once only. Never calculate a dimension from the other dimensions shown on the drawing, nor scale the drawing. There shall be no more dimensions than are necessary to completely define the product. Preferred sizes shall be used whenever possible (see notes). Linear dimensions shall be expressed in millimetres (unit symbol ‘mm’). If this information is stated on the drawing, the unit symbol ‘mm’ may be omitted. If other units are used, the symbols shall be shown with their respective values. Dimensions shall be expressed to the least number of significant figures, e.g. 45 not 45,0. The decimal marker shall be a bold comma, given a full letter space and placed on the baseline. Where four or more numerals are to the left or right of the decimal marker, a full space shall divide each group of three numerals, counting from the position of the decimal marker, e.g. 400 or 100 but 12 500 (see notes). A zero shall precede a decimal of less than one, e.g. 0,5. An angular dimension shall be expressed in degrees and minutes, e.g. 20° and 22° 30’ or, alternatively, as a decimal, e.g. 30,5°. A full space shall be left between the degree symbol and the minute numeral. When an angle is less than one degree, it shall be preceded by a zero, e.g. 0° 30’.
NOTES: Preferred sizes are those referring to standard material stock sizes and standard components such as nuts, bolts, studs and screws. Decimal marker points or commas are not used to separate groups of numerals. This causes ambiguity since the decimal marker is denoted by a comma.
2
The Essential Guide to Technical Product Specification: Engineering Drawing
End product: complete part ready for assembly or service, or a configuration prod
1.3 Types of dimension
from a drawing specification. An end product may also be a part ready for fu
processing (for example, a product from a foundry or forge) or a configuration nee For the purposes of this section, the following definitions apply. further processing.
dimension numerical value expressed in appropriate units of measurement and indicated graphically on technical drawings with lines, symbols and notes 6. Dimensioning of technical drawings Dimensions are classified according to the following types.
functional dimension dimension that is essential to the function of the piece or space (‘F’ in Figure 1). See also 1.14
non-functional dimension dimension that is not essential to the function of the piece or space (‘NF’ in Figure 1) End product: complete part ready for assembly or service, or a configuration produced (a) Design requirement auxiliary dimension from a drawing specification. An end product may also be a part ready for further
Dimension, given for information purposes only,from thatadoes notor govern or inspection processing (for example, a product foundry forge)production or a configuration needing operations and is derived from other values shown on the drawing or in related documents further processing. NOTE: An auxiliary dimension is given in parentheses and no tolerance may be applied to it (‘AUX’ F in Figure F 1).
NF
feature
end product
complete part ready for assembly or service NF or NF configuration produced from a drawing specification (AUX) or ready for assembly or service, or a configuration (a) Design requirement uct: complete part produced part ready for further processing (for example, a product from a foundry (b) or Shoulder forge) orscrew a configuration awing specification. An end product may also be a part ready for further needing further processing g (for example, a product from a foundry or forge) or a configuration needing
ocessing.
F
F
F
NF
NF NF
(a) Design (a)requirement Design requirement
F
F
dimensioning
(AUX)
(b)screw Shoulder screw (b) Shoulder
Figure 1 – Types of dimensioning F
F
F
NF NF
F
F
F
F
NF
NF
F
F
Figure 57: Types of
NF
Threaded hole (c) Threaded(c) hole
F
F
F
Figure individual characteristic such as a flat surface, a cylindrical surface, two parallel surfaces, a shoulder, a 57: Types of 6. Dimensioning of technical drawings dimensioning screw thread, a slot or a profile
3
Dimensioning and tolerancing of size
1.4 Dimensioning conventions Technical product specification standards specify the following conventions when dimensioning drawings. Extension lines shall normally be placed outside the view to aid clarity, as shown in Figure 2. The extension line connects the dimension line (on which the value of the measurement is placed) to the reference points on the outline of the drawing. The following standard practice is specified. Crossing of extension lines shall be avoided whenever possible. There should be a small gap between the outline of the drawing and a projection line. The extension line shall extend slightly beyond the dimension line, as shown in Figure 2. Extension lines shall, where possible, be drawn at right angles to the dimension line. Centre-lines, extensions of centre-lines and continuations of outlines shall never be used as Drawing practice dimension lines. They may, however, be used as projection lines. Arrowheads and origin circles are commonly used as terminators for dimension lines. Oblique strokes and points can also be used, as shown in Figures 3 and 4. Dimension lines shall be unbroken even if the feature they refer to is shown as interrupted, as illustrated in Figure 5.
6. 6. Dimensioning of technical Dimensioning 6. Dimensioning of technical ofdrawings technical drawings draw Leader line
6. Dimensioning 6. Dimensioning 6. Dimensioning of technical of line technical of technical drawings drawings drawing Extension
2 × 45
4500
3500
]
1500
Value of the dimension
When symmetrical are drawn partially, the portions of lines ] When ]symmetrical When parts symmetrical parts areparts drawn arepartially, drawn partially, the portions thethe portions of dimension the dimension of the dimension lines lines Origin indication
Dimension line
Termination (arrowhead)
extend a short way way beyond the of symmetry andsymmetry the second extend aextend short a short beyond wayaxis the beyond axis of thesymmetry axis of and the second andtermination thetermination second istermination is is ] When ] When ]symmetrical When symmetrical symmetrical partsparts are parts drawn are drawn are partially, drawn partially, the partially, portions the portions the of portions the of dimension the ofdimension the dimension lines lines lines omitted, as shown in Figure 62. Figure 2inlines –Figure Examples of extension lines and dimension lines omitted, omitted, asextension shown as shown 62. Figure 62. Figure 58: Examples of andin dimension lines extend extend a short extend a short way a short way beyond beyond waythe beyond axis the of axis the symmetry of axis symmetry of symmetry and the and second the andsecond thetermination second termination termination is is is
omitted, omitted, as omitted, shown as shown as in shown Figure in Figure 62. in Figure 62. 62. Terminators: dimension lines shall be terminated according to one of the representations Figure shown in Figure 3. 59:forTerminato 59: Terminators Figure 59: Figure Terminators for
6.4 Dimensioning conventions
dimension linesdimension dimension lines lines Figure Figure 59:Figure Terminators 59: Terminators 59: Terminators for for fo (c) Arrowhead, 30° 30° open 30° (c) Arrowhead, (c)open Arrowhead, open (b) Arrowhead, (b)closed Arrowhead, closed closed (a) Arrowhead, (a) Arrowhead, (a)closed Arrowhead, closed closed(b) Arrowhead, dimension dimension dimension lines lines lines 30° 30° 30° and filled 30° (BS and filled and 30°8888 filled (BS 8888 30° (BS 8888 (a) Arrowhead, closed and filled 30° (b) Arrowhead, closed 30° Arrowhead, (c) Arrowhead, (c) Arrowhead, (c) (c) Arrowhead, open open 30° open 30°open 30°30° (b) Arrowhead, (b) Arrowhead, (b) Arrowhead, closed closedclosed default) (a) Arrowhead, (a) Arrowhead, (a) Arrowhead, closed closedclosed default) default) 6.4.1 General (BS 8888 default) and filled and filled 30° and(BS filled 30°8888 (BS 30°8888 (BS 8888 30° 30° 30° default) default) default)
Technical product specification standards recommend the following conventions
(d) Arrowhead, open 90° (BS 8888dimensioning (e) Oblique stroke (f) Point (used only if no place for drawings. (d) Arrowhead, 90° when (f) Point (used(used only if no(used (d) Arrowhead, (d)open Arrowhead, open 90° open 90°Oblique (e) stroke (f) Point (f) Point only ifthe nooblique only if no (e) Oblique (e)stroke Oblique stroke non-preferred) arrowhead; stroke may (BS 8888 non-preferred) place for arrowhead; the (BS 8888 (BS non-preferred) 8888 non-preferred) place foralso arrowhead; place be for usedarrowhead; – the BS 8888) the (d) Arrowhead, (d) Arrowhead, (d) Arrowhead, openopen 90° open 90° 90°(e) Oblique oblique stroke may(used also Point (f) Point (used (f) stroke Point (used only ifonly nostroke ifalso only no may if no also (e) Oblique (e)stroke Oblique strokestroke (f) oblique oblique may
6.4.2 Extension lines and dimension lines (BS 8888 (BS 8888 non-preferred) (BS 8888 non-preferred) non-preferred) be used –arrowhead; BS place place forused place for–8888) arrowhead; for arrowhead; the the be be BS used 8888) – BSthe 8888) Figure 3 – Terminators for dimension lines oblique oblique stroke oblique stroke maystroke also may also may also
The extension line connects the dimension (on which value of the measurebe used beline used – be BS used 8888) – BS 8888) – BSthe 8888) ment is placed) to the reference points on the outline of the drawing. The following standard practice is recommended. ]
Figure 60: Origin Figure 60: Figure Origin60: Origin indication indicationindication Figure Figure 60:Figure Origin 60: Origin 60: Origin
Extension lines (continuous narrow line type 01.1.3, see Table 1) should normally indication indication indication
be placed outside of the view to aid clarity, as shown in Figure 58. ]
Crossing of extension lines should be avoided whenever possible.
]
There should be a small gap between the outline of the drawing and a projection interrupted features interrupted interrupted features features
Figure 61: Dimensioning Figure 61: Figure Dimensioning 61: Dimension
line. The extension line should extend slightly beyond the dimension line, as shown Figure Figure 61: Figure Dimensioning 61: Dimensioning 61: Dimensioning
dimension lines (b) Arrowhead, closed
(a) Arrowhead, closed
4
(c) Arrowhead, open 30°
30°Oblique stroke (d) open 90° andArrowhead, filled 30° (BS 8888 (f) Point (used only if no (e) (BS 8888 non-preferred) The Essential Guide to Technical Product default) place for arrowhead; the Specification: Engineering Drawing oblique stroke may also be used – BS 8888)
(d) Arrowhead, open Point (used only if4.no Origin indication: the origin of 90° the dimension line shall be indicated as(f)shown in Figure (e) Oblique stroke (BS 8888 non-preferred)
place for arrowhead; the oblique stroke may also be used – BS 8888)
Figure 60: Origin indication
Figure 4 – Origin indication Figure 60: Origin Figure 61: Dimensioning indication interrupted features
Figure 61: Dimensioning interrupted features
Figure 5 – Dimensioning interrupted features Figure 62: Dimension lines on a partial view of a
When symmetrical parts are drawn partially, the portions of the dimension lines shall extend a short way symmetrical part beyond the axis of symmetry and the second termination shall be omitted, as shown in Figure 6.
Figure 62: Dimension lines on a partial view of a symmetrical part
69
Figure 6 – Dimension lines on a partial view of a symmetrical part
1.5 Arrangement of dimensions The way in which dimensions are typically used on drawings is shown in Figure 7. Conventions for arranging dimensions on drawings are as follows. Dimensions shall be placed in the middle of the dimension line above and clear of it. Dimensions shall not be crossed or separated by other lines on the drawing. Values of angular dimensions shall be oriented so that they can be read from the bottom or the right-hand side of the drawing, as shown in Figure 8. Where space is limited, the dimension can be placed centrally, above, or in line with, the extension of one of the dimension lines, as shown in Figure 9. Larger dimensions shall be placed outside smaller dimensions, as shown in Figure 10.
69
]
Where space is limited, the dimension can be placed centrally, above, or in line with, the extension of one of the dimension lines (see Figure 66).
]
Larger dimensions are placed outside smaller dimensions (see Figure 67).
]
Dimensions of diameters should be placed on the view that provides the greatest
6. Dimensioning of technical5drawings
Dimensioning and tolerancing of size
clarity (see Figure 68).
Dimensions of diameters shall be placed on the view that provides the greatest clarity, as shown in Figure 11. Figure 64: Orientation of
Figure 63: Examples of the
60
ways in which dimensions
linear dimensions
30
are typically used on
60
60
drawings
30
6. Dimensioning of technical drawings 60
60
Figure 7 – Examples of the ways in which dimensions are typically used on drawings (a) 60
60
Figure 64: Orientation of
Figure 65: Orientation of angular dimensions 30
linear 3dimensions 0
60
60 60
60
70 30
Drawing practice Drawing practice
30 60
60
(a)
60
60 (b)
Figure 8 – Orientation of linear and angular dimensions 60
Figure 66: Dimensioning Figure 66: Dimensioning smaller features smaller features
3 3
6 6
60
60
30
60
3 Orientation of Figure30 65: 3 3 3 angular dimensions
Figure 9 – Dimensioning smaller 60 features 60
30
90 90
30
Figure 67: Larger Figure 67: Larger dimensions placed outside dimensions placed outside smaller dimensions smaller dimensions
6 6 60
60
12 12
50 50
60
60
3 3
5050
(a)
3838
(b)
60 30
Figure 10 – Larger dimensions placed outside smaller dimensions
60
71
60 60
0
5
(b)
60
5
60
60
5
Figure 68: Dimensions of Figure 68: Dimensions of diameters placed on view diameters placed on 30view providing the greatest providing the greatest clarity clarity
38
50
6. Dimensioning of technical drawings 6
The Essential Guide to Technical Product Specification: Engineering 6. Drawing Dimensioning of tech
ure 68: Dimensions of
60
meters placed on view
Figure 69: Parallel
oviding the greatest
dimensioning
rity
Figure 6
420
50
45
65
150
35
dimensio
150 640
420 640
Figure 11 – Dimensions of diameters placed on view providing greatest clarity Superimposed running dimensioning is a simplified parallel dimensioning and may Dimensioning from a common feature be used where a number of dimensions of the same direction 6.6 Examples ofcandimensioning methods be used where space limitations. The common origin is shown as in Figure 70. relate to a common origin.there are Superimposed running dimensioning is a simplified parallel dimensioning and may Dimension may be: Dimensioning fromvalues a common maythere be executed parallel dimensioning as superimposed be feature used where are spaceaslimitations. The common or origin is shown as in Figure 70. running dimensioning. Dimensioning from a common feature is used where a number of dimensions of the Dimension values may be: ] Parallel same dimensioning isrelate theofplacement of aorigin. number of single dimension paralleldrawings to one another above and clear dimension line 6. (seeDimensioning Figure 70a); or of lines technical direction tothe a common and spaced ]outinsoline that the dimensional value can easily be added in, as shown in Figure 12a. with the corresponding extension line (see Figure 70b). ] above and clear of the dimension line (see Figure 70a); or Superimposed running dimensioning is a simplified parallel dimensioning and may be used where Dimensioning from a common feature may be executed as parallel dimensioning or70b). as ] in line with is the extension line (see values Figure there are space limitations. The common origin ascorresponding shown in Figure 12. Dimension may be above and clear ofsuperimposed the dimensionrunning line, asdimensioning. shown in Figure 12b; or in line with the corresponding extension line, as shown in Figure 12c. Figure 70: Examples of Parallel dimensioning is the placement of a number of single dimension lines parallel running dimensioning to one another and spaced out so that the dimensional value canFigure easily69: be Parallel added in dimensioning
(see Figure 69).
150
150
420
420 640
a)
running
640 150
(a)
Figure 7
420
(a)
640
b)
Superimposed running dimensioning is a simplified parallel dimensioning and may be used where there are space limitations. The common origin is shown as in Figure 70.
c)
640
(b)
420
in line with the corresponding extension line (see Figure 70b).
640
]
150
above and clear of the dimension line (see Figure 70a); or 150
]
420
Dimension values may be:
Figure 12 – Parallel dimensioning and running dimensioning Figure 70: Examples of (b) running dimensioning
73
Drawing practice
Chain dimensioning consists of a chain of dimensions. These should only be used where the possible accumulation of tolerances does not affect the function of the part 7
Dimensioning andFigure tolerancing (see 71). of size
Chain dimensioning consists of a chain of dimensions. These should only be used Combined dimensioning uses chain dimensioning and parallel dimensioning on the where the possible accumulation of tolerances does not affect the function of the part same drawing (see Figure 72).of of Chain dimensioning consists a chain ofThese dimensions. These only be Chain dimensioning consists dimensions. shall only be should used where theused possible (see Figure 71). of a chain accumulationwhere of tolerances does not affect the ofdoes the part, as shown in Figure the possible accumulation of function tolerances not affect the function of 13. the part Combined uses chain dimensioning and parallel dimensioning on the (see Figuredimensioning 71).
Figure 71: Chain
100
same drawing (see Figure 72). Combined dimensioning uses chain dimensioning and parallel dimensioning on the
dimensioning
same drawing (see Figure 72). 150 100
Figure 71: Chain dimensioning
160
70
200
Figure 13 – Chain dimensioning Figure 72: Examples of
160
70
200
30
150
dimensioning
150 100
Figure 71: Chain
30
combined dimensioning Combined dimensioning uses chain dimensioning and parallel dimensioning on the same drawing view. 160dimensions 70 and parallel 200 dimensioning 30 from a common feature. Figure 14a illustrates combining single
Figure 14b illustrates combining single dimensions and chain dimensions.
Figure 72: Examples of
combined dimensioning Figure 72: Examples of combined dimensioning
(a) Combining single dimensions and parallel dimensioning from a common feature
(a) Combining single dimensions and parallel dimensioning from a common feature
a) (a) Combining single dimensions and parallel dimensioning from a common feature
(b) Combining single dimensions and chain dimensions
b) (b) Combining single dimensions and chain dimensions
74
Figure 14 – Combined dimensioning
(b) Combining single dimensions and chain dimensions
74 74
Dimensioning by coordinates uses superimposed running dimensioning in two direcThe Essential Guide Technical Product Engineering Drawing tions at right angles, as shown in Figure 73. to The common originSpecification: may be any suitable Dimensioning by coordinates uses superimposed running dimensioning in two direccommon reference feature. It may be useful, instead of dimensioning as shown in tions at right angles, as shown in Figure 73. The common origin may be any suitable Figure 73, to tabulate dimensional values as shown in Figure 74. common reference feature. It may be useful, instead of dimensioning as shown in Dimensioning by coordinates uses superimposed running dimensioning in two directions at right angles, Figure 73, to tabulate dimensional values as shown in Figure 74. as shown in Figure 15a. The common origin may be any suitable common reference feature. It may be useful, instead of dimensioning as shown in Figure 15a, to tabulate dimensional values as shown in Figure 73: Dimensioning Figure 15b.
∆ 15 ,5
8
∆ 11
120
∆
∆ 13 ,5
∆
13
13
,5
20
,5
∆
∆
60
13
13
,5
∆ ∆ 13 26 ,5
∆ 13
,5
,5
90 60
∆ 26
∆ 13
,5
∆ 26
120 90
∆ 15 ,5
∆ ∆1 26 5, 5
∆ 11
160
directions)
∆ 15 ,5
160
∆ 15 ,5
∆ 15 ,5
by coordinates (two Figure 73: Dimensioning directions) by coordinates (two
140
180
200
140
180
200
60 60
100
20 20
100
0
0
0
200
a) in two directions Figure 74: Dimensioning
A2 A2
B2 B2 B1
Y
A1
Y
A1
by coordinates (tabulated) Figure 74: Dimensioning by coordinates (tabulated)
C
∆ C
B1
∆
120 90
X X
160 60 120 160 90 60
b) tabulated
Figure 15 – Dimensioning by coordinates 75 75
A diameter of a circle or cylinder is dimensioned by prefixing the value with the symbol Ø. This symbol should be as large as the following numerals and the slanting line 9
tolerancing of size should be aboutDimensioning 30° clockwiseand from the vertical, in the direction in which it is to be read
(see Figure 68). It has already been pointed out (see Figure 68) that the dimensions should be placed on the view that most clearly shows the information.
1.6 Methods for dimensioning common features
Where dimension lines and other lines (e.g. extension lines) would otherwise intersect,
the dimension Certain lines tofeatures, the feature be dimensioned by leaderhole linessizes, as shown suchcan as diameters, radii, squares, chamfers, countersinks and counter-bores, can occur frequently in engineering drawings. in Figure 75. Where the whole view is not shown, concentric diameters can be A diameter of a circle or cylinder shall be dimensioned by prefixing the value with the symbol Ø, dimensioned as in Figure 76. as shown in Figure 16. A square feature shall be dimensioned by prefixing the value with the symbol . Additionally, square and flat features can be indicated by continuous narrow lines drawn diagonally on Circles are to be dimensioned as shown in Figure 77 and spherical surfaces as shown in the flat feature, as shown in Figure 18. Figure 78. Where dimension lines and other lines (e.g. extension lines) would otherwise intersect, the dimension lines to the feature can be dimensioned by leader lines as shown in Figure 16. Where the whole view is not shown, concentric diameters shall be dimensioned as in Figure 17. 6. Dimensionin
25
12. Dimensionin
340 320 300
20
Figure 78: Radial values
R1
0
35 R1 5
30
370
55
Figure 16 – Diameter dimensions indicated by leader lines
Figure 17 – Dimensioning concentric diameters on a partial view 20
10 10
40
Figure 79: Square values
NOTE. Leader line should be in line with centre of circle
40
Figure 18 – Dimensioning a square
SR6
0
SR
12
Figure 80: Spherical radi Circles shall be dimensioned as shown in Figure 19 and spherical surfaces as shown in Figure 20. Radii of features shall be dimensioned by prefixing the value with the letter R. Radii shall bevalues dimensioned by a line that es through, or is in line with, the centre of the arc. The dimension line shall have one arrowhead only, which shall touch the arc. S∆50 Radii that require their centres to be located shall be dimensioned as in Figure 21a; those that do not shall be dimensioned as in Figure 21b. Spherical radii shall be dimensioned as shown in Figures 21c and 21d.
S
20
370
Drawing practice 10 Drawing practice
The Essential Guide to Technical Product Specification: Engineering Drawing
Drawing practice Drawing practice
S∆50
S∆50a Figure 77: Dimensioning
20
10
spherical
circle
10
Figure 78
6.7.3 Radii 6.7.3 Radii
Radii of features are dimensioned by prefixing the value with the letter R. Radii should Radii of features are dimensioned by prefixing the value with the letter R. Radii should NOTE. Leader line should be dimensioned a line that es through, or is in line with, the centre of the arc. 6.7.3 by Radii be in line with centre be dimensioned by a line that es through, or is in line with, the centre of the arc. 6.7.3line Radii The dimension should have one arrowhead only, which should touch the arc. of circle 20 value The dimension should have one arrowhead only,Swhich touch arc. S 20 by prefixing Radiiline of features are dimensioned the the the letter R. Radii should 40 shouldwith Radii of features are dimensioned by prefixing the value with the letter R. Radii should Radii that require their centres bethat located be dimensioned as in Figure 79a; (a) should be dimensioned line es through, or is in line with, the centre of the arc. (a)by ato a) b) (b) Radii that require their centres toline be that located should be dimensioned as in Figure 79a; of the arc. (b) be dimensioned by a es through, or is in line with, the centre those that The do not are dimensioned as in Figure Spherical radiiwhich are dimensioned asthe arc. dimension line should have one79b. arrowhead only, should touch those that do not are dimensioned as in Figure 79b. Spherical radii are dimensioned as the arc. Figure 20 – Dimensioning The dimension line should have one arrowhead only, which should touch shown in Figures 79c and 79d. spherical diameters shown in Figures 79crequire and 79d. Radii that their centres to be located should be dimensioned as in Figure 79a; Radii that require their centres to be located should be dimensioned as in Figure 79a; Figure 19 – Dimensioning a diameter those that do not are dimensioned as in Figure 79b. Spherical radii are dimensioned as Holes are to be dimensioned as shown Figure depth the Holes aredo to not be dimensioned as shown in Figure 79.Spherical Theindepth of79. the drilled holeofwhen those that are dimensioned as in Figure 79b. radii areThe dimensioned as drilled hole w shown in Figures 79c and 79d. given in note form refers to the depth of the cylindrical portion of the given in in Figures noteS∆ form refers to the depth ofFigure the cylindrical portion of the hole and not to hole and n shown 79c and 79d. 78: Dimensioning 50 the extremity made by the point of otherwise the drill, unless R5,5 spherical diameters the extremity made by the point of the drill, unless specified. R4 otherwise specified. R5,5
R4
R4 R4
R2 R2
S 20 R8 R8
(a)
R100 R100
(b)
R2 R2
R8 R8
b)
given in note form refers to the depth of the cylindrical portion of the hole and not to
he extremity made by the point of the drill, unless otherwise specified.
SR6SR 0 60
12 12 c)
Figure 79: Dimensioning radii Figure 79: Dimensioning radii
Figure 79: Dimensioning radii Figure 79: Dimensioning radii
(d) (d)
Figure 21 – Dimensioning radii
d)
(d) (d)
SR6SR60 0
(c) (c)
SR SR
77 SR20 SR20
(c) (c)
SR SR 12 12
SR S R
12 12
SR20 SR20
(b) (b)
SR S R100 12 R1 R100 2
(b)
(a)
a) (b) hole when Holes are to be dimensioned as shown in Figure 79. The depth of the drilled (a)
78 78
R4 R4
5 25 R2 R
(a) (a)
R4 R4
5 5 R2 R2
R5,5 R5,5
13
Holes Holes are dimensioned are dimensioned as shown as shown in Figure in Figure 80. The 80.depth The depth of theofdrilled the drilled hole, hole, whenwhen given given after the afterdiameter, the diameter, refersrefers to thetodepth the depth of theofcylindrical the cylindrical portion portion of theofhole theand hole and not tonot thetoextremity the extremity mademade by thebypoint the point of theofdrill, the unless drill, unless otherwise otherwise specified. specified. 11
Dimensioning and tolerancing of size
∆32
+ 0,02 0
FigureFigure 80: Dimensioning 80: Dimensioning
4 × ∆54 × ∆5
6.7.4 Holes
∆7
∆7
holes holes
Teacher’s note: the method of production (e.g. drill, punch, bore or ream) sh Holes shall be dimensioned as shown in Figure 22. The depth of the drilled hole, when given after the not be specified is essential the function of the drawing. Holestoare shown in Figure 80. Theexcept depth where of the itdrilled hole, to when diameter, refers thedimensioned depth of theas cylindrical portion ∆ 38 ∆of38the hole and not to the extremity made by the theotherwise diameter,specified. refers to the depth of the cylindrical portion of the hole and point of thegiven drill, after unless The method production punch, or drill, ream)unless shall otherwise not be specified except where it is not toofthe extremity (e.g. madedrill, by the pointbore of the specified. essential to the function of the part. + 0,02 + 0,02 + 0,5 0
+ 0,5 0
13
13
∆9,5 ×∆18 9,5 × 18
∆32 arcs 0∆32 and 0 6.7.5 Chords, angles
Figure 80: Dimensioning
4 × ∆5
The dimensioning of chords, as shown in Figure 81 ∆7arcs and angles should beholes
∆32
6.7.56.7.5 Chords, Chords, arcs arcs and angles and angles
105
13
100
+ 0,5 0
∆9,5 × 18
Teacher’s Teacher’s note: note: the method the method of production of production (e.g. drill, (e.g.punch, drill, punch, bore or bore ream) or ream) shouldshould Drawing practice ∆ 38 not benot specified be specified exceptexcept wherewhere it is essential it is essential to thetofunction the function of theofdrawing. the drawing.
+ 0,02 0
Figure 22 – Dimensioning holes
The dimensioning The dimensioning of chords, of chords, arcs and arcsangles and angles should should be asCurved be shown as shown insurfaces Figure in Figure 81. 81. 6.7.6 (b) Arc (a) Chord Teacher’s note: the method of production (e.g. drill, punch, bore or ream) should The dimensioning of chords, arcs and angles shall be as shown in Figure 23. not be specified except where it is essential to thethe function of of theholes drawing. When dimensioning spacing and other features on a curved surf 100
whether the dimensions are chordal or circumferential, they are to be indicated cle Figure Figure 81: 81: Dimensioning 105 105 42Dimensioning
100
chords,chords, arcs and arcsangles and angles on the drawing, as shown in Figure 82.
6.7.5 Chords, arcs and angles Figure 82: Dimensions on
tice
nsions on
800 OUTER SURFACE
The dimensioning arcs and angles should be as a curved surface of chords, shown in Figure 81. (b) Arc(b) Arc
(a) Chord (a) Chord a) chord
(c) Angle
b) arc
Figure100 23 – Dimensioning chords, arcs and 105angles 42
c) angle
Figure 81: Dimensioning chords, arcs and angles
42
Dimensioning the spacing of holes and other features on a curved surface shall be as shown in Figure 24, whethersurfaces the dimensions are chordal or circumferential, they shall be indicated clearly on the drawing. 6.7.6 Curved When dimensioning the spacing of holes and other features on a(b) curved Arc surface, (a) Chord (c) Angle (c) whether the dimensions are chordal or Angle circumferential, they are to be indicated clearly on the drawing, as shown in Figure 82. 42
800 OUTER SURFACE
79
79
(c) Angle
75 +- 0,5
Figure 24 – Dimensions on a curved surface
6.8 Dimensioning screw threads and threade parts
of technical drawing 6.8.2 Thread size6.of Dimensioning The Essential Guide to Technical Product Specification: Engineering Drawing 6.system Dimensioning 6. and Dimensioning technical of technical drawings drawings
12
6. Dimensioning of technical drawings 6. Dimensioning of technical drawings
The letter M, denoting ISO metric screw threads, is followed by the values of th
nominal diameter and pitch (if required), with a multiplication sign between them
1.7 Dimensioning screw threads and threaded parts e.g. M8 × 1.
ISO metric screw threads shall be designated in accordance with BS EN ISO 6410-1, which specifies
6.8.2 Thread system and size 6.8.2 6.8.2 Thread system system and size and size 6.8.3 Thread class that Thread the designation shall indicate the thread system, nominaltolerance diameter and the thread tolerance class. If 6.8.2 Thread system and size 6.8.2 Thread system and size
necessary, the pitch shall also be indicated; however, when designating metric coarse threads, the pitch The letter M, denoting ISO metric screw threads, is followed by the values of the Theisletter TheM, letter denoting M, denoting ISO metric ISO screw metricthreads, screwFor threads, isgeneral followed isuse, followed bythe thetolerance values by the of values the 6H of isthe class suitable for internal threads and toleranc generally omitted. The letter M, denoting ISO metric screw threads, is followed byvalues the values of the The letter M,nominal denoting ISO metric screw threads, is followed by the of the diameter and pitch (if required), with a multiplication sign between them, The nominal diameter to major diameter ofexternal external and threads; the dimension nominal nominal diameter diameter and pitch and(ifrefers pitch required), (if the required), with aclass multiplication with6g a for multiplication sign threads. between ternal between them, them, The thread tolerance class is preceded by a hyphen, e.g nominal diameter and pitch (if required), with a multiplication sign between them, nominal diameter and pitch (if required), with a multiplication sign between them, e.g. of M8thread × 1. refers to the full depth of thread. The direction of a right hand thread (RH) to the×depth e.g.relating M8e.g. × 1. M8 1. M10-6H or M10 × 1-6g. e.g. M8 × 1. e.g. M8 × 1. is not generally noted; however left hand threads shall be denoted with the abbreviation ‘LH’ after the thread designation. 6.8.3 Thread toleranceScrew classthreads are dimensioned as shown in Figures 83 and 84.
6.8.3 Thread 6.8.3 Thread tolerance tolerance class class 6.8.3 Thread 6.8.3 Thread classclass Thread system andtolerance sizetolerance
M36-6g
M20-6g
For general use, the tolerance class 6Hbe is followed suitable for threads tolerance letter M, denoting ISO metric threads, by internal the values of theand nominal diameter ForThe general For general use, theuse, tolerance the tolerance class 6Hscrew class is suitable 6H is suitable for shall internal for internal threads threads and tolerance and tolerance For general use, the tolerance class 6H is suitable for internal threads and tolerance For general use, the tolerance class 6H is suitable for internal threads and tolerance and pitch (if required), with multiplication them, e.g. M8 × 1. class 6g foraexternal threads.sign The between thread tolerance class is preceded by a hyphen, e.g. class 6gclass for external 6g for external threads.threads. The thread The tolerance thread tolerance class is preceded class is preceded by a hyphen, by a hyphen, e.g. e.g. class for external threads. The thread tolerance class is preceded by a hyphen, class 6g for6g external threads. The thread tolerance class is preceded by a hyphen, e.g. e.g. M10-6H or M10 × 1-6g. 40 30 min M10-6H M10-6H or tolerance M10 or × M10 1-6g. × 1-6g. Thread class M10-6H or M10 × 1-6g. M10-6H or M10 × 1-6g. full For general use, the tolerance class 6H is suitable for internal threads and tolerance class 6g for external thread Screw threadsclass are dimensioned as shown Figures 83 and 84. threads. Thethreads thread tolerance shall be preceded by83 a in hyphen, Screw threads Screw are dimensioned are dimensioned as shown as in shown Figures in Figures 83 and 84. and 84. e.g. M10-6H or M10 × 1-6g. Screw threads are dimensioned as shown in Figures 83 and 84. Screw threads are dimensioned as shown in Figures 83 and 84.
Screw threads shall be dimensioned as shown in Figures 25 and 26.
M20-6g
M20-6g
M20-6g
M20-6g M20-6g
40
M36-6g
M36-6g
(a) (a) (a)
Figure 83: Dimensioning (b) 30 min Figure 83: Figure Dimensioning 83: Dimensioning 30 min 30 min Figure 83: Dimensioning Figure 83: Dimensioning external screw threads 30 min30 min full thread external external screw threads screw threads full thread full thread external screw threads external screw threads full thread full thread
40
40 40
M12-6H x 16 38 max
38 max 38 15max min 38 max38 max (b)full thread (b) (b) (b) (b)
(a) a)
b)
Figure 25 – Dimensioning external screw threads
(a) (a)
a) (a)
(a)
(b) b) (b) (b)
16
16 (a)
16
(b) Figure 84: Dimensioning Figure 84: Figure Dimensioning 84: Dimensioning M12 x 1,25-6H FigureFigure 84: Dimensioning 84: Dimensioning internal screw threads M12 x 1,25-6H M12 x 1,25-6H internal screw internal threads screw threads x 1,25-6H M12 xM12 1,25-6H internal threads internal screw screw threads
1616
(a)
M12-6H x 16 M12-6H M12-6H x 16 x 16 1516min M12-6H x M12-6H x 16 15 min 15 min full thread 15 min 15 full thread fullmin thread full thread full thread
M12 x 1,25-6H
16
(a)
M36-6g M36-6g
M36-6g
40
38 max
(a)
(b)
(b)
M6-6H x 10 20 min full thread c) including run-out 28 max
(c) Figure 26 – Dimensioning internal screw threads
M6-6H x 10 M6-6H xM6-6H 10 x 10 20 M6-6H x 10 min full thread M6-6H x 10 20 min full 20 thread min full thread 28thread max including run-out 20 min full 20 min full thread 28 max including 28 max including run-out run-out max including run-out 28 max28including run-out (c) (c) (c) (c) (c)
81
81 81 81
8
1
45°, the indications may be simplified as shown in Figures 104 and 105.
Note. Methods of production (e.g. ‘drill’, ‘punch’, ‘bore’, ‘ream’)+should not be 0,02 specified, except where they are essential to the function.
∆32
0
Dimensioning and tolerancing of size
∆13
or
4 × ∆5
13.7 Chamfers and countersinks ∆7 30 ˚
1.8 Dimensioning chamfers and 2
∆9,5 × 18 countersinks
Figure13 103: Chamfer dimensioning Figure 102: Hole dimensioning
30 ˚
13
+ 0,5 0
Chamfers should be dimensioned as shown in Figure 103. Where ∆ 38 the chamfer angle is Chamfers shall be dimensioned as shown in Figure 27. Where the chamfer angle is 45°, the indications 45°, the indications may be simplified as shown in Figures 104 and 105. may be simplified as shown in Figure 28.
Figure 104: 45° chamfer
2 × 45 ˚
+ 0,02 ∆32 0
30 ˚
simplified Figure 103: Chamfer
∆13
or or
dimensioning
13.7 Chamfers and countersinks 30 ˚
2
2 × 45 ˚
Chamfers should be dimensioned as shown in Figure 103. Where the chamfer angle is 45°, the indications may be simplified as shown in Figures 104 and 105. 22××45 45˚ ˚
2 × 45 ˚
Figure 105: Dimensionin Figure 104: 45° chamfer internal chamfers simplified Figure 103: Chamfer
or
or or
∆13
dimensioning
30 ˚
2 × 45 ˚
30 ˚
2
Figure 27 – Dimensioning external and internal chamfers
Figure 105: Dimensionin
2 × 45 ˚ 2 × 45 ˚
2 × 45 ˚ or
internal chamfers Figure 104: 45° chamfer simplified
113
or
Engineering drawing practice
2 × 45 ˚
Figure 28 – Simplified dimensioning of chamfers 2 × 45 ˚
Figure 105: Dimensionin internal chamfers
Countersinks are dimensioned by showing either the required diametral dimension at 2 × 45 ˚ Countersinks shall be dimensioned by showing either the required diametral dimension at the included the included angle, or the depth and the included angle 113 (see Figure 106). or angle, or the depth and the included angle, as shown in Figure 29. Figure 106: Dimensioning
90 ˚
90 ˚
∆14
countersinks
or
113
3,5
Figure 29 – Dimensioning countersinks
13.8 Other indications The use of reference letters in conjunction with an explanatory note or table can also be
50
13.5 Equally spaced repeated features 14
The Essential Guide to Technical Product Specification: Engineering Drawing
Where repeated features are linearly spaced, a simplified method of dimensioning may
13.5 Equally spaced repeated features be used, as illustrated in Figure 95.
1.9 Equally spaced repeated features
Where features areone linearly spaced, a simplified method of dimensioning may If thererepeated is any ambiguity, feature space may be dimensioned as illustrated in be used, as illustrated in Figure 95. Where repeated are linearly spaced, a simplified method of dimensioning may be used, as Figurefeatures 96. shown in Figure 30. If there is any ambiguity, one feature space may be dimensioned as illustrated in
ure 95: Dimensioning
inear spacings
Figure 96.
ure 95: Dimensioning
inear spacings
15
5 × 18 (= 90)
Figure 30 – Dimensioning of linear spacings
15
5 × 18 (= 90)
ure 96: Dimensioning
inear spacings If to there avoid is any ambiguity, one feature space may be dimensioned as illustrated in Figure 31.
nfusion
ure 96: Dimensioning
inear spacings to avoid
18
nfusion
17 × 18 (= 306)
15 18
17 be × 18dimensioned (= 306) 15 equally spaced features may Angular, as illustrated in Figure 97.
13. Dimensioning from a common feature Figure Dimensioning of linear spacings to avoid confusion The angles of 31 the –spacings may be omitted when the intent is evident, as shown in Angular, equally spaced features may be dimensioned as illustrated in Figure 97. Figure 98.
Angular, equally spaced shall bebedimensioned asindirectly shown in 32. The of of the The angles offeatures the spacings may be omitted when the intent is evident, shown in spacings Circular spaced features may dimensioned byFigure specifying theasangle number can be omitted where the intent is explicit, as shown in Figure 33. Figure 98.features, common as illustrated in Figure 99. Circular spaced features may be dimensioned indirectly by specifying the number of common features, as illustrated in Figure 99.
15 ˚
Figure 97: Dimensioning of angular spacings
110
10 ˚ 3
0' 110
5 × 10 ˚ 30' (52 ˚ 30')
Figure 32 – Dimensioning angular spacing ∆50
Figure 98: The omission of angles of spacings to avoid confusion
4 × ∆9
15 ˚
Figure 97: Dimensioning
10 ˚ 3
0'
of angular spacings 15
Dimensioning and tolerancing of size
5 × 10 ˚ 30' (52 ˚ 30')
15 ˚
∆50
10 ˚ 3
0'
Figure 98: The omission
angles of spacings to avo confusion
5 × 10 ˚ 30' (52 ˚ 30')
4 × ∆9
∆50
Figure 98: The omission
angles of spacings to avo confusion
4 × ∆9
5× Figure 33 – Omission of angle of spacing
16
Figure 99: Dimensioning circular spacings
6 Circular spaced features can be dimensioned indirectly by specifying the number of common features as shown in Figure 34.
Figure 99: Dimensioning
5×
16
circular spacings
6
5 × ∆12
5 × ∆12
111
Figure 34 – Dimensioning circular spacings
111
16
The Essential Guide to Technical Product Specification: Engineering Drawing
Series or patterned features of the same size may be dimensioned as illustrated in Figuresor100 and 101. Series patterned features of the same size may be dimensioned as illustrated in Figures 100 and of 101. Series or patterned features the same size may be dimensioned as illustrated in Figures 35 and 36.
ure 100: Defining a
antity of elements of the ure 100: Defining a me size: linear antity of elements of the
8 × ∆8 8 × ∆8
me size: linear
Figure 35 – Dimensioning a quantity of features of the same size – linear
ure 101: Defining a
6 × ∆8
antity of elements of the ure 101: Defining a me size: circular antity of elements of the
6 × ∆8
me size: circular
13.636Holes Figure – Dimensioning a quantity of features of the same size – circular 13.6 Holes Holes are dimensioned as shown in Figure 102. The depth of the drilled hole, when
1.10 Dimensioning of curved profiles given after the diameter, referinto the depth of the cylindrical of thewhen hole Holes are dimensioned asshall shown Figure 102. The depth of the portion drilled hole,
and not to the the diameter, extremity made by the point of the unless otherwise specified. given after shall tobe the depth of drill, the by cylindrical hole37. Curved profiles composed of circular arcsrefer shall dimensioned radii, asportion shown of inthe Figure and not to thepoints extremity by surface, the pointasofshown the drill, unless otherwise specified. Coordinates locating on amade curved in Figure 38, shall only be used when the profile is not composed of circular arcs. The more coordinates specified, the better the uniformity of the curve.
112 112
12.9. Curved profiles composed of circular arcs should be dimensioned by radii, as illustrated
17
Dimensioning and tolerancing of size
in Figure 118.
Figure 118: The
dimensioning of a curved profile
Engineering drawing practice
Figure 37 – Dimensioning of a curved profile Figure 119: Linear coordinates of a series of points through which a profile es 119
Figure 38 – Linear coordinates of a series of points through which a profile es
Coordinates locating points on a curved surface, as illustrated in Figure 119, should
1.11 Dimensioning of keyways
only be used when the profile is not composed of circular arcs. The more coordinates
specified, the uniformity Keyways in hubs or shafts shallthe bebetter dimensioned by oneofofthe thecurve. methods shown in Figure 39. NOTE: Further information on keys and keyways is given in BS 4235-1, Specification for metric keys and keyways – Part 1: Figure 120 illustrates a method specifying a cam in association with a Parallel and taper keys and BS 4235-2, Specification for metricof keys and keyways – Partprofile 2: Woodruff keys and keyways.
follower. The follower is indicated by a long-dashed double-dotted narrow line type 05.1.1 (see Table 1).
Figure 120: Specifying dimensions in association with a follower
0˚
b
shown in Figure 5. NOTE Further information on keys and keyways is given in BS 4235-1, Specification for metric keys and keyways – Part 1: Parallel and taper keys, and BS 4235-2, Specification for metric keys and keyways – Part 2: Woodruff keys and keyways. The Essential Guide to Technical Product Specification: Engineering Drawing
18
Figure 5
Dimensioning of keyways
a) Parallel hub
d) Parallel shaft
f) Parallel shaft
b) Tapered keyway in parallel hub
c) Parallel keyway in tapered hub
e) Parallel keyway in tapered shaft
g) Tapered shaft
Figure 39 – Dimensioning of keyways
1.12 Tolerancing
© BSI 2006 •
21
Tolerancing is the practice of specifying the upper and lower limit for any permissible variation in the finished manufactured size of a feature. The difference between these limits is known as the tolerance for that dimension. All dimensions (except auxiliary dimensions) are subject to tolerances. Tolerances shall be specified for all dimensions that affect the functioning or interchange ability of the part. Tolerances shall also be used to indicate where unusually wide variations are permissible. Tolerances shall be applied either to individual dimensions or by a general note giving uniform or graded tolerances to classes of dimensions, for example: TOLERANCE UNLESS OTHERWISE STATED LINEAR ±0,4 ANGULAR ±0° 30’ The method shown in Figure 40a should be followed where it is required to tolerance individual linear dimensions. This method directly specifies both the limits of the size of the dimension, the tolerance being the difference between the limits of the size. The larger limit of the size shall be placed above the smaller limit and both shall be given to the same number of decimal places. The method shown in Figure 40b can be used as an alternative way of specifying tolerances.
6.9.3 Tolerancing of individual linear dimensions The method shown in Figure 85 is recommended where it is required to tolerance indi-
Dimensioning andThis tolerancing size specifies both the limits of the size of the6. Dimensioning of technical 19 vidual linear dimensions. method of directly drawin dimension, the tolerance being the difference between the limits of the size.
32,15 31,80
nce by
32
+0,15 -0,20
f size
The larger limit of the size is placed above the smaller limit, and both are given to the
a) places. same number of decimal
b)
Figure 40 – Linear dimension tolerance by directly specifying limits of size 6.9.4 Tolerancing of individual angular dimensions The methods shown41 in Figure 86used may be to tolerance individual angular dimensions. The methods shown in Figure may be to used tolerance individual angular dimensions.
Figure 86: Tolerancing
30 30' 30 0'
(a)
(b)
a)
0 30,5 ± 0,1
90 ± 0 30'
angular dimensions
(c)
b)
c)
Figure 41 – Tolerancing angular dimensions
6.10 Summary
1.13 Interpretations of limits ofparts size forstandards a feature-of-size This chapter has covered those of the that deal with dimensioning and
tolerancing which are likely to be of use to Design and Technology teachers and their Limits of size for an individual feature-of-size shall be interpreted according to the principles and rules students in schools and colleges. The key points are as follows. defined in BS ISO 8015, BS EN ISO 14660-1 and BS EN ISO 14660-2. A feature-of-size may consist of two parallel plane surfaces, a cylindrical surface or a spherical BIP 2155 File name: 2008-01133_40b.e ] The general principles dimensioning as set out in may BS 8888:2006 should always surface, in each case defined with a of linear size. A feature-of-size also consist of two plane surfaces at an angle to each other (aifwedge) a conical surface, in each defined with an angular be followed effectiveorcommunication between thecase designer, manufacturer and size. BS ISO 8015 states that limits of size control only the actual local sizes (two-point measurements) end is to be established and maintained. of a feature-of-size and not its deviations of form (e.g. the roundness and straightness deviations of a ] Functional dimensions are those that directly affect the function of the product. cylindrical feature, or the flatness deviations of two parallel plane surfaces). Form deviations may be ] All dimensions except auxiliary dimensions are subject to tolerancing. controlled by individually specified geometrical tolerances, general geometrical tolerances or through ] envelope The decimal marker is represented by a comma not a point. the use of the requirement (where the maximum material limit of size defines an envelope of perfect form]forGroups the relevant surfaces; seeleft BS and ISO right 8015). of numerals to the of the decimal marker should be divided BS ISO 8015 defines the principle of independency, according to which specified up into groups of three, counting from the decimal marker, and aeach full space, notdimensional a and geometrical requirement on a drawing is met independently, unless a particular relationship is comma, left between them. specified. A relationship may be specified through the use of the envelope requirement or material condition modifiers maximum material condition (MMC) or least material condition (LMC). Where no relationship is specified, any geometrical tolerance applied to the feature-of-size applies regardless of feature size, and the two requirements shall be treated as unrelated, as shown in Figure 42. Relevant standards Title The limits of size do not control the form, orientation, or the spatial relationship between, individual Technical drawings — Dimensioning and features-of-size.BS EN ISO 1660
Consequently, if a particular relationship of size and form, or size and location, or size and tolerancing of profiles orientation is required, it needs to be specified. BS ISO 129-1 Technical drawings — Indication of dimensions and tolerances — Part 1: General principles
BS 8888:2008
BritiSh Standard
20
The Essential Guide to Technical Product Specification: Engineering Drawing
25,0 24,9
Figure 3 Permissible interpretations when no form control is given on the drawing
a) drawing presentation
a
b
c
NOTE There is no form control (i.e. over roundness, straightness or cylindricity). Measurements a, b and c may lie between 25.0 mm and 24.9 mm, meeting the drawing requirement using two-point measurement only. b) Permissible interpretation: straightness unconstrained
Maximum size
5,0
2
Maximum roundness deviation (resulting from a lobed form)
NOTE For any cross-section of the cylinder, there is no roundness control. c) Permissible interpretation: roundness unconstrained
Figure 42 – Permissible interpretations when no form control is given on the drawing 15.1.2 Limits of size with mutual dependency of size and form COMMENTARY AND RECOMMENDATIONS ON 15.1.2
1.13.1 Limits of size with mutual dependency of size and form Some national standards apply, or have applied, the Envelope Requirement to all features-of-size by default. As the Envelope Requirement the default, they have not used a symbol by to Some national standards apply, or have applied, has the been envelope requirement to all features-of-size indicate this requirement; rather they use a note to indicate when this default. As the envelope requirement has been the default, they have not used a symbol to indicate this is not required. This system of tolerancing is sometimes described as the requirement; rather they use a note Principle to indicate when this is or notthe required. Thisofsystem of tolerancing of Dependency, application the Taylor Principle. is sometimes described as the principle of dependency, or the theEnvelope Taylor principle. Standards which apply, or application have applied,ofthe Requirement by Standards which apply, or have default applied, the envelope requirement by default include: include: ASME Y14.5 (the requirement that there is an envelope of perfect form corresponding to the Maximum Material Size of the feature is The requirement that there shall be an envelope perfect defined asofRule #1). form corresponding to the maximum
ASME Y14.5
material size of the feature is defined asBS Rule 308#1). (the Principle of Dependency was taken as the default option under BS 308, although the option of working to the Principle of Independency was included, through the use of The principle of dependency was taken as the optionI indication): under BS 308, although the option of working the BSdefault 308 triangle
BS 308
I
8888 to the principle of independency was included, through the use of theBS BS 308 triangle I indication.
BS 8888 prior to the 2004 revision (the Principle of Dependency was I taken option under BS 8888:2000 and BS 8888:2002, BS as 8888the default although the option of working to the Principle of Independency was included, through the use of the BS 8888 triangle I indication).
16 • © BSI 2008
21
Dimensioning and tolerancing of size
BS 8888 Prior to the 2004 revision; the principle of dependency was taken as the default option under BS 8888:2000 and BS 8888:2002, although the option of working to the principle of independency was included, through the use of the BS 8888 triangle I indication.
BS 8888:2004 and BS 8888:2006 the principle of dependency could be explicitly invoked through the use of the BS 8888 triangle D indication. BS 8888
D
As the interaction between the envelope requirement and individual geometrical tolerances is not always fully defined within the ISO system, and as the application of the envelope requirement by default to all features-of-size is not formally ed within the ISO system, the use of the principle of dependency is no longer recommended.
1.14 Datum surfaces and functional requirements Functional dimensions shall be expressed directly on the drawing, as shown in Figure 1. The application of this principle will result in the selection of reference features on the basis of the function of the product and the method of locating it in any assembly of which it may form a part. If any reference feature other than one based on the function of the product is used, finer tolerances will be necessary to meet the functional requirement, which in turn will increase the cost of producing the product, as shown in Figure 43 on page 22.
1.15 Relevant standards BS EN ISO 1660, Technical drawings — Dimensioning and tolerancing of profiles BS ISO 129-1, Technical drawings — Indication of dimensions and tolerances — Part 1: General principles BS ISO 3040, Technical drawings — Dimensioning and tolerancing — Cones BS ISO 10579, Technical drawings — Dimensioning and tolerancing — Non-rigid parts BS ISO 406, Technical drawings — Tolerancing of linear and angular dimensions BS EN 22768-1, General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications BS 4235-1, Specification for metric keys and keyways — Part 1: Parallel and taper keys BS 4235-2, Specification for metric keys and keyways — Part 2: Woodruff keys and keyways BS ISO 8015, Technical drawings — Fundamental tolerancing principle BS EN ISO 14660-1, Geometrical Product Specifications (GPS) — Geometrical features — Part 1: General and definitions BS EN ISO 14660-2, Geometrical Product Specifications (GPS) — Geometrical features — Part 2: Extracted median line of a cylinder and a cone, extracted median surface, local size of an extracted feature PP 8888-2, Engineering drawing practice: a guide for further and higher education to BS 8888:2006, Technical product specification (TPS)
A
22
The Essential Guide to Technical Product Specification: Engineering Drawing
Description
Drawing
1
2
12,00 11,92
Date: 15/06/2009 Approval of issue 6,05 6,00
5,5 5,0
NOTE: One direct dimension with a tolerance of 0.05 mm is needed to satisfy the condition shown in a). A nominal flange thickness of 5 mm has been assumed. This value is non-functional and can have BIPany 2155 large tolerance.
Modifications:
File name: 2008-01133_43a.eps
correct functional reference surface
d) Item 2 dimensioned from a nonfunctional reference surface
File name: 2008-01133_43b.eps
BSI/PM: Jenny Cranwell Date: 15/06/2009
BIP 2155
11,03 11,00
5,00 4,98
NOTE: Tolerances have had to be reduced; two dimensions with tolerances of, say, 0.02 mm for the flange and 0.03 mm are now needed to satisfy the condition shown in a).
incorrect non-functional reference surface
Figure 43 – Effect on tolerances by changing datum surfaces from those determined by functional requirements
BIP 2155
Date: 15/06/2009 Modifications:
c) Item 2 dimensioned from a functional reference surface
18,00 17,97
b) Detail of head of item 1 showing given limits of size, with a tolerance of 0.03 mm
Modifications:
3
BSI/PM: Jenny Cranwell Approval of issue
a) Assembly drawing showing a given functional requirement, namely the limits of height of the top face of item 1 above the top face of item 3, with a tolerance of 0.08 mm
File name: 2008-01133_43c.eps
Colin Simmons and Neil Phelps
First published in the UK in 2009 by BSI 389 Chiswick High Road London W4 4AL
© British Standards Institution 2009 All rights reserved. Except as permitted under the Copyright, Designs and Patents Act 1988, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means – electronic, photocopying, recording or otherwise – without prior permission in writing from the publisher. Whilst every care has been taken in developing and compiling this publication, BSI accepts no liability for any loss or damage caused, arising directly or indirectly in connection with reliance on its contents except to the extent that such liability may not be excluded in law. While every effort has been made to trace all copyright holders, anyone claiming copyright should get in touch with the BSI at the above address. BSI has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this book, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. The right of Colin Simmons and Neil Phelps to be identified as the authors of this Work has been asserted by them in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988.
Typeset in Optima and Gill Sans by Monolith – http://www.monolith.uk.com Printed in Great Britain by Berforts Group, Stevenage
British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 978 0 580 62673 9
v
Contents Introduction Dimensioning and tolerancing of size 1.1 Introduction 1.2 General principles 1.3 Types of dimension 1.4 Dimensioning conventions 1.5 Arrangement of dimensions 1.6 Methods for dimensioning common features 1.7 Dimensioning screw threads and threaded parts 1.8 Dimensioning chamfers and countersinks 1.9 Equally spaced repeated features 1.10 Dimensioning of curved profiles 1.11 Dimensioning of keyways 1.12 Tolerancing 1.13 Interpretations of limits of size for a feature-of-size 1.14 Datum surfaces and functional requirements 1.15 Relevant standards Geometric tolerancing datums and datum systems 2.1 Introduction 2.2 and definitions 2.3 Basic concepts 2.4 Symbols 2.5 Tolerance frame 2.6 Toleranced features 2.7 Tolerance zones 2.8 Datums and datum systems 2.9 Supplementary indications 2.10 Examples of geometrical tolerancing 2.11 Relevant standards Graphical symbols for the indication of surface texture 3.1 Introduction 3.2 The basic graphical symbol 3.3 Expanded graphical symbols 3.4 Mandatory positions for the indication of surface texture requirements 3.5 Surface texture parameters 3.6 Indication of special surface texture characteristics 3.7 Indications on drawings 3.8 Relevant standards
vii 1 1 1 2 3 4 9 12 13 14 16 17 18 19 21 21 23 23 23 26 27 29 29 32 37 45 64 114 115 115 115 115 116 117 118 120 123
vi
The Essential Guide to Technical Product Specification: Engineering Drawing
Welding, brazed and soldered ts – Symbolic representation 4.1 Introduction 4.2 Relevant standards Limits and fits 5.1 Introduction 5.2 Selected ISO fits – Hole basis 5.3 Selected ISO fits – Shaft basis 5.4 Methods of specifying required fits 5.5 Relevant standards Metric screw threads 6.1 Introduction 6.2 Thread designation 6.3 Relevant standards Illustrated index to BS 8888 Normative references
125 125 133 135 135 135 138 140 140 141 141 141 168 169 169
vii
Introduction This guide has been produced as a companion to BS 8888, presenting up-to-date information based on the technical product specification aspects of BS 8888 and the essential standards it references. Its aim is to offer straightforward guidance together with pictorial representations, to all practitioners of technical product specification, i.e. those currently using BS 8888 and those who, in a bid to conform to global ISO practices, are making or wish to make, the transition from the old BS 308 to BS 8888. Its scope is to provide the necessary tools to enable engineers engaged in design specification, manufacturing and verification with the essential basic information required for specifying a product or component. It includes comprehensive sections extracted from and referenced to international standards relating to linear, geometric and surface texture dimensioning and tolerancing, together with the practice of welding symbology, limits and fits and thread data. It also includes an illustrated index to all standards referenced in BS 8888. This guide does not replace BS 8888 which is the definitive standard for technical product realization. Any element of BS 8888 not included in this guide should not be considered as less important to technical specification than those included. Most of the drawings in this guide have been extracted (and adapted) from the following BSI publications: BS EN ISO 1101, BS EN ISO 1302, BS ISO 5459, BS 8888 and PP 8888, Parts 1 and 2.
1
Chapter 1 Dimensioning and tolerancing of size 1.1 Introduction Dimensioning is the process of applying measurements to a technical drawing. It is crucial to the whole process by which the designer will communicate the information required for the manufacture and verification of products.
1.2 General principles Dimensions shall be applied to the drawing accurately, clearly and unambiguously. The following points shall be regarded as general dimensioning principles to be applied to all technical drawings. • • • • •
• • •
• • • •
Each dimension necessary for the definition of the finished product shall be shown once only. Never calculate a dimension from the other dimensions shown on the drawing, nor scale the drawing. There shall be no more dimensions than are necessary to completely define the product. Preferred sizes shall be used whenever possible (see notes). Linear dimensions shall be expressed in millimetres (unit symbol ‘mm’). If this information is stated on the drawing, the unit symbol ‘mm’ may be omitted. If other units are used, the symbols shall be shown with their respective values. Dimensions shall be expressed to the least number of significant figures, e.g. 45 not 45,0. The decimal marker shall be a bold comma, given a full letter space and placed on the baseline. Where four or more numerals are to the left or right of the decimal marker, a full space shall divide each group of three numerals, counting from the position of the decimal marker, e.g. 400 or 100 but 12 500 (see notes). A zero shall precede a decimal of less than one, e.g. 0,5. An angular dimension shall be expressed in degrees and minutes, e.g. 20° and 22° 30’ or, alternatively, as a decimal, e.g. 30,5°. A full space shall be left between the degree symbol and the minute numeral. When an angle is less than one degree, it shall be preceded by a zero, e.g. 0° 30’.
NOTES: Preferred sizes are those referring to standard material stock sizes and standard components such as nuts, bolts, studs and screws. Decimal marker points or commas are not used to separate groups of numerals. This causes ambiguity since the decimal marker is denoted by a comma.
2
The Essential Guide to Technical Product Specification: Engineering Drawing
End product: complete part ready for assembly or service, or a configuration prod
1.3 Types of dimension
from a drawing specification. An end product may also be a part ready for fu
processing (for example, a product from a foundry or forge) or a configuration nee For the purposes of this section, the following definitions apply. further processing.
dimension numerical value expressed in appropriate units of measurement and indicated graphically on technical drawings with lines, symbols and notes 6. Dimensioning of technical drawings Dimensions are classified according to the following types.
functional dimension dimension that is essential to the function of the piece or space (‘F’ in Figure 1). See also 1.14
non-functional dimension dimension that is not essential to the function of the piece or space (‘NF’ in Figure 1) End product: complete part ready for assembly or service, or a configuration produced (a) Design requirement auxiliary dimension from a drawing specification. An end product may also be a part ready for further
Dimension, given for information purposes only,from thatadoes notor govern or inspection processing (for example, a product foundry forge)production or a configuration needing operations and is derived from other values shown on the drawing or in related documents further processing. NOTE: An auxiliary dimension is given in parentheses and no tolerance may be applied to it (‘AUX’ F in Figure F 1).
NF
feature
end product
complete part ready for assembly or service NF or NF configuration produced from a drawing specification (AUX) or ready for assembly or service, or a configuration (a) Design requirement uct: complete part produced part ready for further processing (for example, a product from a foundry (b) or Shoulder forge) orscrew a configuration awing specification. An end product may also be a part ready for further needing further processing g (for example, a product from a foundry or forge) or a configuration needing
ocessing.
F
F
F
NF
NF NF
(a) Design (a)requirement Design requirement
F
F
dimensioning
(AUX)
(b)screw Shoulder screw (b) Shoulder
Figure 1 – Types of dimensioning F
F
F
NF NF
F
F
F
F
NF
NF
F
F
Figure 57: Types of
NF
Threaded hole (c) Threaded(c) hole
F
F
F
Figure individual characteristic such as a flat surface, a cylindrical surface, two parallel surfaces, a shoulder, a 57: Types of 6. Dimensioning of technical drawings dimensioning screw thread, a slot or a profile
3
Dimensioning and tolerancing of size
1.4 Dimensioning conventions Technical product specification standards specify the following conventions when dimensioning drawings. Extension lines shall normally be placed outside the view to aid clarity, as shown in Figure 2. The extension line connects the dimension line (on which the value of the measurement is placed) to the reference points on the outline of the drawing. The following standard practice is specified. Crossing of extension lines shall be avoided whenever possible. There should be a small gap between the outline of the drawing and a projection line. The extension line shall extend slightly beyond the dimension line, as shown in Figure 2. Extension lines shall, where possible, be drawn at right angles to the dimension line. Centre-lines, extensions of centre-lines and continuations of outlines shall never be used as Drawing practice dimension lines. They may, however, be used as projection lines. Arrowheads and origin circles are commonly used as terminators for dimension lines. Oblique strokes and points can also be used, as shown in Figures 3 and 4. Dimension lines shall be unbroken even if the feature they refer to is shown as interrupted, as illustrated in Figure 5.
6. 6. Dimensioning of technical Dimensioning 6. Dimensioning of technical ofdrawings technical drawings draw Leader line
6. Dimensioning 6. Dimensioning 6. Dimensioning of technical of line technical of technical drawings drawings drawing Extension
2 × 45
4500
3500
]
1500
Value of the dimension
When symmetrical are drawn partially, the portions of lines ] When ]symmetrical When parts symmetrical parts areparts drawn arepartially, drawn partially, the portions thethe portions of dimension the dimension of the dimension lines lines Origin indication
Dimension line
Termination (arrowhead)
extend a short way way beyond the of symmetry andsymmetry the second extend aextend short a short beyond wayaxis the beyond axis of thesymmetry axis of and the second andtermination thetermination second istermination is is ] When ] When ]symmetrical When symmetrical symmetrical partsparts are parts drawn are drawn are partially, drawn partially, the partially, portions the portions the of portions the of dimension the ofdimension the dimension lines lines lines omitted, as shown in Figure 62. Figure 2inlines –Figure Examples of extension lines and dimension lines omitted, omitted, asextension shown as shown 62. Figure 62. Figure 58: Examples of andin dimension lines extend extend a short extend a short way a short way beyond beyond waythe beyond axis the of axis the symmetry of axis symmetry of symmetry and the and second the andsecond thetermination second termination termination is is is
omitted, omitted, as omitted, shown as shown as in shown Figure in Figure 62. in Figure 62. 62. Terminators: dimension lines shall be terminated according to one of the representations Figure shown in Figure 3. 59:forTerminato 59: Terminators Figure 59: Figure Terminators for
6.4 Dimensioning conventions
dimension linesdimension dimension lines lines Figure Figure 59:Figure Terminators 59: Terminators 59: Terminators for for fo (c) Arrowhead, 30° 30° open 30° (c) Arrowhead, (c)open Arrowhead, open (b) Arrowhead, (b)closed Arrowhead, closed closed (a) Arrowhead, (a) Arrowhead, (a)closed Arrowhead, closed closed(b) Arrowhead, dimension dimension dimension lines lines lines 30° 30° 30° and filled 30° (BS and filled and 30°8888 filled (BS 8888 30° (BS 8888 (a) Arrowhead, closed and filled 30° (b) Arrowhead, closed 30° Arrowhead, (c) Arrowhead, (c) Arrowhead, (c) (c) Arrowhead, open open 30° open 30°open 30°30° (b) Arrowhead, (b) Arrowhead, (b) Arrowhead, closed closedclosed default) (a) Arrowhead, (a) Arrowhead, (a) Arrowhead, closed closedclosed default) default) 6.4.1 General (BS 8888 default) and filled and filled 30° and(BS filled 30°8888 (BS 30°8888 (BS 8888 30° 30° 30° default) default) default)
Technical product specification standards recommend the following conventions
(d) Arrowhead, open 90° (BS 8888dimensioning (e) Oblique stroke (f) Point (used only if no place for drawings. (d) Arrowhead, 90° when (f) Point (used(used only if no(used (d) Arrowhead, (d)open Arrowhead, open 90° open 90°Oblique (e) stroke (f) Point (f) Point only ifthe nooblique only if no (e) Oblique (e)stroke Oblique stroke non-preferred) arrowhead; stroke may (BS 8888 non-preferred) place for arrowhead; the (BS 8888 (BS non-preferred) 8888 non-preferred) place foralso arrowhead; place be for usedarrowhead; – the BS 8888) the (d) Arrowhead, (d) Arrowhead, (d) Arrowhead, openopen 90° open 90° 90°(e) Oblique oblique stroke may(used also Point (f) Point (used (f) stroke Point (used only ifonly nostroke ifalso only no may if no also (e) Oblique (e)stroke Oblique strokestroke (f) oblique oblique may
6.4.2 Extension lines and dimension lines (BS 8888 (BS 8888 non-preferred) (BS 8888 non-preferred) non-preferred) be used –arrowhead; BS place place forused place for–8888) arrowhead; for arrowhead; the the be be BS used 8888) – BSthe 8888) Figure 3 – Terminators for dimension lines oblique oblique stroke oblique stroke maystroke also may also may also
The extension line connects the dimension (on which value of the measurebe used beline used – be BS used 8888) – BS 8888) – BSthe 8888) ment is placed) to the reference points on the outline of the drawing. The following standard practice is recommended. ]
Figure 60: Origin Figure 60: Figure Origin60: Origin indication indicationindication Figure Figure 60:Figure Origin 60: Origin 60: Origin
Extension lines (continuous narrow line type 01.1.3, see Table 1) should normally indication indication indication
be placed outside of the view to aid clarity, as shown in Figure 58. ]
Crossing of extension lines should be avoided whenever possible.
]
There should be a small gap between the outline of the drawing and a projection interrupted features interrupted interrupted features features
Figure 61: Dimensioning Figure 61: Figure Dimensioning 61: Dimension
line. The extension line should extend slightly beyond the dimension line, as shown Figure Figure 61: Figure Dimensioning 61: Dimensioning 61: Dimensioning
dimension lines (b) Arrowhead, closed
(a) Arrowhead, closed
4
(c) Arrowhead, open 30°
30°Oblique stroke (d) open 90° andArrowhead, filled 30° (BS 8888 (f) Point (used only if no (e) (BS 8888 non-preferred) The Essential Guide to Technical Product default) place for arrowhead; the Specification: Engineering Drawing oblique stroke may also be used – BS 8888)
(d) Arrowhead, open Point (used only if4.no Origin indication: the origin of 90° the dimension line shall be indicated as(f)shown in Figure (e) Oblique stroke (BS 8888 non-preferred)
place for arrowhead; the oblique stroke may also be used – BS 8888)
Figure 60: Origin indication
Figure 4 – Origin indication Figure 60: Origin Figure 61: Dimensioning indication interrupted features
Figure 61: Dimensioning interrupted features
Figure 5 – Dimensioning interrupted features Figure 62: Dimension lines on a partial view of a
When symmetrical parts are drawn partially, the portions of the dimension lines shall extend a short way symmetrical part beyond the axis of symmetry and the second termination shall be omitted, as shown in Figure 6.
Figure 62: Dimension lines on a partial view of a symmetrical part
69
Figure 6 – Dimension lines on a partial view of a symmetrical part
1.5 Arrangement of dimensions The way in which dimensions are typically used on drawings is shown in Figure 7. Conventions for arranging dimensions on drawings are as follows. Dimensions shall be placed in the middle of the dimension line above and clear of it. Dimensions shall not be crossed or separated by other lines on the drawing. Values of angular dimensions shall be oriented so that they can be read from the bottom or the right-hand side of the drawing, as shown in Figure 8. Where space is limited, the dimension can be placed centrally, above, or in line with, the extension of one of the dimension lines, as shown in Figure 9. Larger dimensions shall be placed outside smaller dimensions, as shown in Figure 10.
69
]
Where space is limited, the dimension can be placed centrally, above, or in line with, the extension of one of the dimension lines (see Figure 66).
]
Larger dimensions are placed outside smaller dimensions (see Figure 67).
]
Dimensions of diameters should be placed on the view that provides the greatest
6. Dimensioning of technical5drawings
Dimensioning and tolerancing of size
clarity (see Figure 68).
Dimensions of diameters shall be placed on the view that provides the greatest clarity, as shown in Figure 11. Figure 64: Orientation of
Figure 63: Examples of the
60
ways in which dimensions
linear dimensions
30
are typically used on
60
60
drawings
30
6. Dimensioning of technical drawings 60
60
Figure 7 – Examples of the ways in which dimensions are typically used on drawings (a) 60
60
Figure 64: Orientation of
Figure 65: Orientation of angular dimensions 30
linear 3dimensions 0
60
60 60
60
70 30
Drawing practice Drawing practice
30 60
60
(a)
60
60 (b)
Figure 8 – Orientation of linear and angular dimensions 60
Figure 66: Dimensioning Figure 66: Dimensioning smaller features smaller features
3 3
6 6
60
60
30
60
3 Orientation of Figure30 65: 3 3 3 angular dimensions
Figure 9 – Dimensioning smaller 60 features 60
30
90 90
30
Figure 67: Larger Figure 67: Larger dimensions placed outside dimensions placed outside smaller dimensions smaller dimensions
6 6 60
60
12 12
50 50
60
60
3 3
5050
(a)
3838
(b)
60 30
Figure 10 – Larger dimensions placed outside smaller dimensions
60
71
60 60
0
5
(b)
60
5
60
60
5
Figure 68: Dimensions of Figure 68: Dimensions of diameters placed on view diameters placed on 30view providing the greatest providing the greatest clarity clarity
38
50
6. Dimensioning of technical drawings 6
The Essential Guide to Technical Product Specification: Engineering 6. Drawing Dimensioning of tech
ure 68: Dimensions of
60
meters placed on view
Figure 69: Parallel
oviding the greatest
dimensioning
rity
Figure 6
420
50
45
65
150
35
dimensio
150 640
420 640
Figure 11 – Dimensions of diameters placed on view providing greatest clarity Superimposed running dimensioning is a simplified parallel dimensioning and may Dimensioning from a common feature be used where a number of dimensions of the same direction 6.6 Examples ofcandimensioning methods be used where space limitations. The common origin is shown as in Figure 70. relate to a common origin.there are Superimposed running dimensioning is a simplified parallel dimensioning and may Dimension may be: Dimensioning fromvalues a common maythere be executed parallel dimensioning as superimposed be feature used where are spaceaslimitations. The common or origin is shown as in Figure 70. running dimensioning. Dimensioning from a common feature is used where a number of dimensions of the Dimension values may be: ] Parallel same dimensioning isrelate theofplacement of aorigin. number of single dimension paralleldrawings to one another above and clear dimension line 6. (seeDimensioning Figure 70a); or of lines technical direction tothe a common and spaced ]outinsoline that the dimensional value can easily be added in, as shown in Figure 12a. with the corresponding extension line (see Figure 70b). ] above and clear of the dimension line (see Figure 70a); or Superimposed running dimensioning is a simplified parallel dimensioning and may be used where Dimensioning from a common feature may be executed as parallel dimensioning or70b). as ] in line with is the extension line (see values Figure there are space limitations. The common origin ascorresponding shown in Figure 12. Dimension may be above and clear ofsuperimposed the dimensionrunning line, asdimensioning. shown in Figure 12b; or in line with the corresponding extension line, as shown in Figure 12c. Figure 70: Examples of Parallel dimensioning is the placement of a number of single dimension lines parallel running dimensioning to one another and spaced out so that the dimensional value canFigure easily69: be Parallel added in dimensioning
(see Figure 69).
150
150
420
420 640
a)
running
640 150
(a)
Figure 7
420
(a)
640
b)
Superimposed running dimensioning is a simplified parallel dimensioning and may be used where there are space limitations. The common origin is shown as in Figure 70.
c)
640
(b)
420
in line with the corresponding extension line (see Figure 70b).
640
]
150
above and clear of the dimension line (see Figure 70a); or 150
]
420
Dimension values may be:
Figure 12 – Parallel dimensioning and running dimensioning Figure 70: Examples of (b) running dimensioning
73
Drawing practice
Chain dimensioning consists of a chain of dimensions. These should only be used where the possible accumulation of tolerances does not affect the function of the part 7
Dimensioning andFigure tolerancing (see 71). of size
Chain dimensioning consists of a chain of dimensions. These should only be used Combined dimensioning uses chain dimensioning and parallel dimensioning on the where the possible accumulation of tolerances does not affect the function of the part same drawing (see Figure 72).of of Chain dimensioning consists a chain ofThese dimensions. These only be Chain dimensioning consists dimensions. shall only be should used where theused possible (see Figure 71). of a chain accumulationwhere of tolerances does not affect the ofdoes the part, as shown in Figure the possible accumulation of function tolerances not affect the function of 13. the part Combined uses chain dimensioning and parallel dimensioning on the (see Figuredimensioning 71).
Figure 71: Chain
100
same drawing (see Figure 72). Combined dimensioning uses chain dimensioning and parallel dimensioning on the
dimensioning
same drawing (see Figure 72). 150 100
Figure 71: Chain dimensioning
160
70
200
Figure 13 – Chain dimensioning Figure 72: Examples of
160
70
200
30
150
dimensioning
150 100
Figure 71: Chain
30
combined dimensioning Combined dimensioning uses chain dimensioning and parallel dimensioning on the same drawing view. 160dimensions 70 and parallel 200 dimensioning 30 from a common feature. Figure 14a illustrates combining single
Figure 14b illustrates combining single dimensions and chain dimensions.
Figure 72: Examples of
combined dimensioning Figure 72: Examples of combined dimensioning
(a) Combining single dimensions and parallel dimensioning from a common feature
(a) Combining single dimensions and parallel dimensioning from a common feature
a) (a) Combining single dimensions and parallel dimensioning from a common feature
(b) Combining single dimensions and chain dimensions
b) (b) Combining single dimensions and chain dimensions
74
Figure 14 – Combined dimensioning
(b) Combining single dimensions and chain dimensions
74 74
Dimensioning by coordinates uses superimposed running dimensioning in two direcThe Essential Guide Technical Product Engineering Drawing tions at right angles, as shown in Figure 73. to The common originSpecification: may be any suitable Dimensioning by coordinates uses superimposed running dimensioning in two direccommon reference feature. It may be useful, instead of dimensioning as shown in tions at right angles, as shown in Figure 73. The common origin may be any suitable Figure 73, to tabulate dimensional values as shown in Figure 74. common reference feature. It may be useful, instead of dimensioning as shown in Dimensioning by coordinates uses superimposed running dimensioning in two directions at right angles, Figure 73, to tabulate dimensional values as shown in Figure 74. as shown in Figure 15a. The common origin may be any suitable common reference feature. It may be useful, instead of dimensioning as shown in Figure 15a, to tabulate dimensional values as shown in Figure 73: Dimensioning Figure 15b.
∆ 15 ,5
8
∆ 11
120
∆
∆ 13 ,5
∆
13
13
,5
20
,5
∆
∆
60
13
13
,5
∆ ∆ 13 26 ,5
∆ 13
,5
,5
90 60
∆ 26
∆ 13
,5
∆ 26
120 90
∆ 15 ,5
∆ ∆1 26 5, 5
∆ 11
160
directions)
∆ 15 ,5
160
∆ 15 ,5
∆ 15 ,5
by coordinates (two Figure 73: Dimensioning directions) by coordinates (two
140
180
200
140
180
200
60 60
100
20 20
100
0
0
0
200
a) in two directions Figure 74: Dimensioning
A2 A2
B2 B2 B1
Y
A1
Y
A1
by coordinates (tabulated) Figure 74: Dimensioning by coordinates (tabulated)
C
∆ C
B1
∆
120 90
X X
160 60 120 160 90 60
b) tabulated
Figure 15 – Dimensioning by coordinates 75 75
A diameter of a circle or cylinder is dimensioned by prefixing the value with the symbol Ø. This symbol should be as large as the following numerals and the slanting line 9
tolerancing of size should be aboutDimensioning 30° clockwiseand from the vertical, in the direction in which it is to be read
(see Figure 68). It has already been pointed out (see Figure 68) that the dimensions should be placed on the view that most clearly shows the information.
1.6 Methods for dimensioning common features
Where dimension lines and other lines (e.g. extension lines) would otherwise intersect,
the dimension Certain lines tofeatures, the feature be dimensioned by leaderhole linessizes, as shown suchcan as diameters, radii, squares, chamfers, countersinks and counter-bores, can occur frequently in engineering drawings. in Figure 75. Where the whole view is not shown, concentric diameters can be A diameter of a circle or cylinder shall be dimensioned by prefixing the value with the symbol Ø, dimensioned as in Figure 76. as shown in Figure 16. A square feature shall be dimensioned by prefixing the value with the symbol . Additionally, square and flat features can be indicated by continuous narrow lines drawn diagonally on Circles are to be dimensioned as shown in Figure 77 and spherical surfaces as shown in the flat feature, as shown in Figure 18. Figure 78. Where dimension lines and other lines (e.g. extension lines) would otherwise intersect, the dimension lines to the feature can be dimensioned by leader lines as shown in Figure 16. Where the whole view is not shown, concentric diameters shall be dimensioned as in Figure 17. 6. Dimensionin
25
12. Dimensionin
340 320 300
20
Figure 78: Radial values
R1
0
35 R1 5
30
370
55
Figure 16 – Diameter dimensions indicated by leader lines
Figure 17 – Dimensioning concentric diameters on a partial view 20
10 10
40
Figure 79: Square values
NOTE. Leader line should be in line with centre of circle
40
Figure 18 – Dimensioning a square
SR6
0
SR
12
Figure 80: Spherical radi Circles shall be dimensioned as shown in Figure 19 and spherical surfaces as shown in Figure 20. Radii of features shall be dimensioned by prefixing the value with the letter R. Radii shall bevalues dimensioned by a line that es through, or is in line with, the centre of the arc. The dimension line shall have one arrowhead only, which shall touch the arc. S∆50 Radii that require their centres to be located shall be dimensioned as in Figure 21a; those that do not shall be dimensioned as in Figure 21b. Spherical radii shall be dimensioned as shown in Figures 21c and 21d.
S
20
370
Drawing practice 10 Drawing practice
The Essential Guide to Technical Product Specification: Engineering Drawing
Drawing practice Drawing practice
S∆50
S∆50a Figure 77: Dimensioning
20
10
spherical
circle
10
Figure 78
6.7.3 Radii 6.7.3 Radii
Radii of features are dimensioned by prefixing the value with the letter R. Radii should Radii of features are dimensioned by prefixing the value with the letter R. Radii should NOTE. Leader line should be dimensioned a line that es through, or is in line with, the centre of the arc. 6.7.3 by Radii be in line with centre be dimensioned by a line that es through, or is in line with, the centre of the arc. 6.7.3line Radii The dimension should have one arrowhead only, which should touch the arc. of circle 20 value The dimension should have one arrowhead only,Swhich touch arc. S 20 by prefixing Radiiline of features are dimensioned the the the letter R. Radii should 40 shouldwith Radii of features are dimensioned by prefixing the value with the letter R. Radii should Radii that require their centres bethat located be dimensioned as in Figure 79a; (a) should be dimensioned line es through, or is in line with, the centre of the arc. (a)by ato a) b) (b) Radii that require their centres toline be that located should be dimensioned as in Figure 79a; of the arc. (b) be dimensioned by a es through, or is in line with, the centre those that The do not are dimensioned as in Figure Spherical radiiwhich are dimensioned asthe arc. dimension line should have one79b. arrowhead only, should touch those that do not are dimensioned as in Figure 79b. Spherical radii are dimensioned as the arc. Figure 20 – Dimensioning The dimension line should have one arrowhead only, which should touch shown in Figures 79c and 79d. spherical diameters shown in Figures 79crequire and 79d. Radii that their centres to be located should be dimensioned as in Figure 79a; Radii that require their centres to be located should be dimensioned as in Figure 79a; Figure 19 – Dimensioning a diameter those that do not are dimensioned as in Figure 79b. Spherical radii are dimensioned as Holes are to be dimensioned as shown Figure depth the Holes aredo to not be dimensioned as shown in Figure 79.Spherical Theindepth of79. the drilled holeofwhen those that are dimensioned as in Figure 79b. radii areThe dimensioned as drilled hole w shown in Figures 79c and 79d. given in note form refers to the depth of the cylindrical portion of the given in in Figures noteS∆ form refers to the depth ofFigure the cylindrical portion of the hole and not to hole and n shown 79c and 79d. 78: Dimensioning 50 the extremity made by the point of otherwise the drill, unless R5,5 spherical diameters the extremity made by the point of the drill, unless specified. R4 otherwise specified. R5,5
R4
R4 R4
R2 R2
S 20 R8 R8
(a)
R100 R100
(b)
R2 R2
R8 R8
b)
given in note form refers to the depth of the cylindrical portion of the hole and not to
he extremity made by the point of the drill, unless otherwise specified.
SR6SR 0 60
12 12 c)
Figure 79: Dimensioning radii Figure 79: Dimensioning radii
Figure 79: Dimensioning radii Figure 79: Dimensioning radii
(d) (d)
Figure 21 – Dimensioning radii
d)
(d) (d)
SR6SR60 0
(c) (c)
SR SR
77 SR20 SR20
(c) (c)
SR SR 12 12
SR S R
12 12
SR20 SR20
(b) (b)
SR S R100 12 R1 R100 2
(b)
(a)
a) (b) hole when Holes are to be dimensioned as shown in Figure 79. The depth of the drilled (a)
78 78
R4 R4
5 25 R2 R
(a) (a)
R4 R4
5 5 R2 R2
R5,5 R5,5
13
Holes Holes are dimensioned are dimensioned as shown as shown in Figure in Figure 80. The 80.depth The depth of theofdrilled the drilled hole, hole, whenwhen given given after the afterdiameter, the diameter, refersrefers to thetodepth the depth of theofcylindrical the cylindrical portion portion of theofhole theand hole and not tonot thetoextremity the extremity mademade by thebypoint the point of theofdrill, the unless drill, unless otherwise otherwise specified. specified. 11
Dimensioning and tolerancing of size
∆32
+ 0,02 0
FigureFigure 80: Dimensioning 80: Dimensioning
4 × ∆54 × ∆5
6.7.4 Holes
∆7
∆7
holes holes
Teacher’s note: the method of production (e.g. drill, punch, bore or ream) sh Holes shall be dimensioned as shown in Figure 22. The depth of the drilled hole, when given after the not be specified is essential the function of the drawing. Holestoare shown in Figure 80. Theexcept depth where of the itdrilled hole, to when diameter, refers thedimensioned depth of theas cylindrical portion ∆ 38 ∆of38the hole and not to the extremity made by the theotherwise diameter,specified. refers to the depth of the cylindrical portion of the hole and point of thegiven drill, after unless The method production punch, or drill, ream)unless shall otherwise not be specified except where it is not toofthe extremity (e.g. madedrill, by the pointbore of the specified. essential to the function of the part. + 0,02 + 0,02 + 0,5 0
+ 0,5 0
13
13
∆9,5 ×∆18 9,5 × 18
∆32 arcs 0∆32 and 0 6.7.5 Chords, angles
Figure 80: Dimensioning
4 × ∆5
The dimensioning of chords, as shown in Figure 81 ∆7arcs and angles should beholes
∆32
6.7.56.7.5 Chords, Chords, arcs arcs and angles and angles
105
13
100
+ 0,5 0
∆9,5 × 18
Teacher’s Teacher’s note: note: the method the method of production of production (e.g. drill, (e.g.punch, drill, punch, bore or bore ream) or ream) shouldshould Drawing practice ∆ 38 not benot specified be specified exceptexcept wherewhere it is essential it is essential to thetofunction the function of theofdrawing. the drawing.
+ 0,02 0
Figure 22 – Dimensioning holes
The dimensioning The dimensioning of chords, of chords, arcs and arcsangles and angles should should be asCurved be shown as shown insurfaces Figure in Figure 81. 81. 6.7.6 (b) Arc (a) Chord Teacher’s note: the method of production (e.g. drill, punch, bore or ream) should The dimensioning of chords, arcs and angles shall be as shown in Figure 23. not be specified except where it is essential to thethe function of of theholes drawing. When dimensioning spacing and other features on a curved surf 100
whether the dimensions are chordal or circumferential, they are to be indicated cle Figure Figure 81: 81: Dimensioning 105 105 42Dimensioning
100
chords,chords, arcs and arcsangles and angles on the drawing, as shown in Figure 82.
6.7.5 Chords, arcs and angles Figure 82: Dimensions on
tice
nsions on
800 OUTER SURFACE
The dimensioning arcs and angles should be as a curved surface of chords, shown in Figure 81. (b) Arc(b) Arc
(a) Chord (a) Chord a) chord
(c) Angle
b) arc
Figure100 23 – Dimensioning chords, arcs and 105angles 42
c) angle
Figure 81: Dimensioning chords, arcs and angles
42
Dimensioning the spacing of holes and other features on a curved surface shall be as shown in Figure 24, whethersurfaces the dimensions are chordal or circumferential, they shall be indicated clearly on the drawing. 6.7.6 Curved When dimensioning the spacing of holes and other features on a(b) curved Arc surface, (a) Chord (c) Angle (c) whether the dimensions are chordal or Angle circumferential, they are to be indicated clearly on the drawing, as shown in Figure 82. 42
800 OUTER SURFACE
79
79
(c) Angle
75 +- 0,5
Figure 24 – Dimensions on a curved surface
6.8 Dimensioning screw threads and threade parts
of technical drawing 6.8.2 Thread size6.of Dimensioning The Essential Guide to Technical Product Specification: Engineering Drawing 6.system Dimensioning 6. and Dimensioning technical of technical drawings drawings
12
6. Dimensioning of technical drawings 6. Dimensioning of technical drawings
The letter M, denoting ISO metric screw threads, is followed by the values of th
nominal diameter and pitch (if required), with a multiplication sign between them
1.7 Dimensioning screw threads and threaded parts e.g. M8 × 1.
ISO metric screw threads shall be designated in accordance with BS EN ISO 6410-1, which specifies
6.8.2 Thread system and size 6.8.2 6.8.2 Thread system system and size and size 6.8.3 Thread class that Thread the designation shall indicate the thread system, nominaltolerance diameter and the thread tolerance class. If 6.8.2 Thread system and size 6.8.2 Thread system and size
necessary, the pitch shall also be indicated; however, when designating metric coarse threads, the pitch The letter M, denoting ISO metric screw threads, is followed by the values of the Theisletter TheM, letter denoting M, denoting ISO metric ISO screw metricthreads, screwFor threads, isgeneral followed isuse, followed bythe thetolerance values by the of values the 6H of isthe class suitable for internal threads and toleranc generally omitted. The letter M, denoting ISO metric screw threads, is followed byvalues the values of the The letter M,nominal denoting ISO metric screw threads, is followed by the of the diameter and pitch (if required), with a multiplication sign between them, The nominal diameter to major diameter ofexternal external and threads; the dimension nominal nominal diameter diameter and pitch and(ifrefers pitch required), (if the required), with aclass multiplication with6g a for multiplication sign threads. between ternal between them, them, The thread tolerance class is preceded by a hyphen, e.g nominal diameter and pitch (if required), with a multiplication sign between them, nominal diameter and pitch (if required), with a multiplication sign between them, e.g. of M8thread × 1. refers to the full depth of thread. The direction of a right hand thread (RH) to the×depth e.g.relating M8e.g. × 1. M8 1. M10-6H or M10 × 1-6g. e.g. M8 × 1. e.g. M8 × 1. is not generally noted; however left hand threads shall be denoted with the abbreviation ‘LH’ after the thread designation. 6.8.3 Thread toleranceScrew classthreads are dimensioned as shown in Figures 83 and 84.
6.8.3 Thread 6.8.3 Thread tolerance tolerance class class 6.8.3 Thread 6.8.3 Thread classclass Thread system andtolerance sizetolerance
M36-6g
M20-6g
For general use, the tolerance class 6Hbe is followed suitable for threads tolerance letter M, denoting ISO metric threads, by internal the values of theand nominal diameter ForThe general For general use, theuse, tolerance the tolerance class 6Hscrew class is suitable 6H is suitable for shall internal for internal threads threads and tolerance and tolerance For general use, the tolerance class 6H is suitable for internal threads and tolerance For general use, the tolerance class 6H is suitable for internal threads and tolerance and pitch (if required), with multiplication them, e.g. M8 × 1. class 6g foraexternal threads.sign The between thread tolerance class is preceded by a hyphen, e.g. class 6gclass for external 6g for external threads.threads. The thread The tolerance thread tolerance class is preceded class is preceded by a hyphen, by a hyphen, e.g. e.g. class for external threads. The thread tolerance class is preceded by a hyphen, class 6g for6g external threads. The thread tolerance class is preceded by a hyphen, e.g. e.g. M10-6H or M10 × 1-6g. 40 30 min M10-6H M10-6H or tolerance M10 or × M10 1-6g. × 1-6g. Thread class M10-6H or M10 × 1-6g. M10-6H or M10 × 1-6g. full For general use, the tolerance class 6H is suitable for internal threads and tolerance class 6g for external thread Screw threadsclass are dimensioned as shown Figures 83 and 84. threads. Thethreads thread tolerance shall be preceded by83 a in hyphen, Screw threads Screw are dimensioned are dimensioned as shown as in shown Figures in Figures 83 and 84. and 84. e.g. M10-6H or M10 × 1-6g. Screw threads are dimensioned as shown in Figures 83 and 84. Screw threads are dimensioned as shown in Figures 83 and 84.
Screw threads shall be dimensioned as shown in Figures 25 and 26.
M20-6g
M20-6g
M20-6g
M20-6g M20-6g
40
M36-6g
M36-6g
(a) (a) (a)
Figure 83: Dimensioning (b) 30 min Figure 83: Figure Dimensioning 83: Dimensioning 30 min 30 min Figure 83: Dimensioning Figure 83: Dimensioning external screw threads 30 min30 min full thread external external screw threads screw threads full thread full thread external screw threads external screw threads full thread full thread
40
40 40
M12-6H x 16 38 max
38 max 38 15max min 38 max38 max (b)full thread (b) (b) (b) (b)
(a) a)
b)
Figure 25 – Dimensioning external screw threads
(a) (a)
a) (a)
(a)
(b) b) (b) (b)
16
16 (a)
16
(b) Figure 84: Dimensioning Figure 84: Figure Dimensioning 84: Dimensioning M12 x 1,25-6H FigureFigure 84: Dimensioning 84: Dimensioning internal screw threads M12 x 1,25-6H M12 x 1,25-6H internal screw internal threads screw threads x 1,25-6H M12 xM12 1,25-6H internal threads internal screw screw threads
1616
(a)
M12-6H x 16 M12-6H M12-6H x 16 x 16 1516min M12-6H x M12-6H x 16 15 min 15 min full thread 15 min 15 full thread fullmin thread full thread full thread
M12 x 1,25-6H
16
(a)
M36-6g M36-6g
M36-6g
40
38 max
(a)
(b)
(b)
M6-6H x 10 20 min full thread c) including run-out 28 max
(c) Figure 26 – Dimensioning internal screw threads
M6-6H x 10 M6-6H xM6-6H 10 x 10 20 M6-6H x 10 min full thread M6-6H x 10 20 min full 20 thread min full thread 28thread max including run-out 20 min full 20 min full thread 28 max including 28 max including run-out run-out max including run-out 28 max28including run-out (c) (c) (c) (c) (c)
81
81 81 81
8
1
45°, the indications may be simplified as shown in Figures 104 and 105.
Note. Methods of production (e.g. ‘drill’, ‘punch’, ‘bore’, ‘ream’)+should not be 0,02 specified, except where they are essential to the function.
∆32
0
Dimensioning and tolerancing of size
∆13
or
4 × ∆5
13.7 Chamfers and countersinks ∆7 30 ˚
1.8 Dimensioning chamfers and 2
∆9,5 × 18 countersinks
Figure13 103: Chamfer dimensioning Figure 102: Hole dimensioning
30 ˚
13
+ 0,5 0
Chamfers should be dimensioned as shown in Figure 103. Where ∆ 38 the chamfer angle is Chamfers shall be dimensioned as shown in Figure 27. Where the chamfer angle is 45°, the indications 45°, the indications may be simplified as shown in Figures 104 and 105. may be simplified as shown in Figure 28.
Figure 104: 45° chamfer
2 × 45 ˚
+ 0,02 ∆32 0
30 ˚
simplified Figure 103: Chamfer
∆13
or or
dimensioning
13.7 Chamfers and countersinks 30 ˚
2
2 × 45 ˚
Chamfers should be dimensioned as shown in Figure 103. Where the chamfer angle is 45°, the indications may be simplified as shown in Figures 104 and 105. 22××45 45˚ ˚
2 × 45 ˚
Figure 105: Dimensionin Figure 104: 45° chamfer internal chamfers simplified Figure 103: Chamfer
or
or or
∆13
dimensioning
30 ˚
2 × 45 ˚
30 ˚
2
Figure 27 – Dimensioning external and internal chamfers
Figure 105: Dimensionin
2 × 45 ˚ 2 × 45 ˚
2 × 45 ˚ or
internal chamfers Figure 104: 45° chamfer simplified
113
or
Engineering drawing practice
2 × 45 ˚
Figure 28 – Simplified dimensioning of chamfers 2 × 45 ˚
Figure 105: Dimensionin internal chamfers
Countersinks are dimensioned by showing either the required diametral dimension at 2 × 45 ˚ Countersinks shall be dimensioned by showing either the required diametral dimension at the included the included angle, or the depth and the included angle 113 (see Figure 106). or angle, or the depth and the included angle, as shown in Figure 29. Figure 106: Dimensioning
90 ˚
90 ˚
∆14
countersinks
or
113
3,5
Figure 29 – Dimensioning countersinks
13.8 Other indications The use of reference letters in conjunction with an explanatory note or table can also be
50
13.5 Equally spaced repeated features 14
The Essential Guide to Technical Product Specification: Engineering Drawing
Where repeated features are linearly spaced, a simplified method of dimensioning may
13.5 Equally spaced repeated features be used, as illustrated in Figure 95.
1.9 Equally spaced repeated features
Where features areone linearly spaced, a simplified method of dimensioning may If thererepeated is any ambiguity, feature space may be dimensioned as illustrated in be used, as illustrated in Figure 95. Where repeated are linearly spaced, a simplified method of dimensioning may be used, as Figurefeatures 96. shown in Figure 30. If there is any ambiguity, one feature space may be dimensioned as illustrated in
ure 95: Dimensioning
inear spacings
Figure 96.
ure 95: Dimensioning
inear spacings
15
5 × 18 (= 90)
Figure 30 – Dimensioning of linear spacings
15
5 × 18 (= 90)
ure 96: Dimensioning
inear spacings If to there avoid is any ambiguity, one feature space may be dimensioned as illustrated in Figure 31.
nfusion
ure 96: Dimensioning
inear spacings to avoid
18
nfusion
17 × 18 (= 306)
15 18
17 be × 18dimensioned (= 306) 15 equally spaced features may Angular, as illustrated in Figure 97.
13. Dimensioning from a common feature Figure Dimensioning of linear spacings to avoid confusion The angles of 31 the –spacings may be omitted when the intent is evident, as shown in Angular, equally spaced features may be dimensioned as illustrated in Figure 97. Figure 98.
Angular, equally spaced shall bebedimensioned asindirectly shown in 32. The of of the The angles offeatures the spacings may be omitted when the intent is evident, shown in spacings Circular spaced features may dimensioned byFigure specifying theasangle number can be omitted where the intent is explicit, as shown in Figure 33. Figure 98.features, common as illustrated in Figure 99. Circular spaced features may be dimensioned indirectly by specifying the number of common features, as illustrated in Figure 99.
15 ˚
Figure 97: Dimensioning of angular spacings
110
10 ˚ 3
0' 110
5 × 10 ˚ 30' (52 ˚ 30')
Figure 32 – Dimensioning angular spacing ∆50
Figure 98: The omission of angles of spacings to avoid confusion
4 × ∆9
15 ˚
Figure 97: Dimensioning
10 ˚ 3
0'
of angular spacings 15
Dimensioning and tolerancing of size
5 × 10 ˚ 30' (52 ˚ 30')
15 ˚
∆50
10 ˚ 3
0'
Figure 98: The omission
angles of spacings to avo confusion
5 × 10 ˚ 30' (52 ˚ 30')
4 × ∆9
∆50
Figure 98: The omission
angles of spacings to avo confusion
4 × ∆9
5× Figure 33 – Omission of angle of spacing
16
Figure 99: Dimensioning circular spacings
6 Circular spaced features can be dimensioned indirectly by specifying the number of common features as shown in Figure 34.
Figure 99: Dimensioning
5×
16
circular spacings
6
5 × ∆12
5 × ∆12
111
Figure 34 – Dimensioning circular spacings
111
16
The Essential Guide to Technical Product Specification: Engineering Drawing
Series or patterned features of the same size may be dimensioned as illustrated in Figuresor100 and 101. Series patterned features of the same size may be dimensioned as illustrated in Figures 100 and of 101. Series or patterned features the same size may be dimensioned as illustrated in Figures 35 and 36.
ure 100: Defining a
antity of elements of the ure 100: Defining a me size: linear antity of elements of the
8 × ∆8 8 × ∆8
me size: linear
Figure 35 – Dimensioning a quantity of features of the same size – linear
ure 101: Defining a
6 × ∆8
antity of elements of the ure 101: Defining a me size: circular antity of elements of the
6 × ∆8
me size: circular
13.636Holes Figure – Dimensioning a quantity of features of the same size – circular 13.6 Holes Holes are dimensioned as shown in Figure 102. The depth of the drilled hole, when
1.10 Dimensioning of curved profiles given after the diameter, referinto the depth of the cylindrical of thewhen hole Holes are dimensioned asshall shown Figure 102. The depth of the portion drilled hole,
and not to the the diameter, extremity made by the point of the unless otherwise specified. given after shall tobe the depth of drill, the by cylindrical hole37. Curved profiles composed of circular arcsrefer shall dimensioned radii, asportion shown of inthe Figure and not to thepoints extremity by surface, the pointasofshown the drill, unless otherwise specified. Coordinates locating on amade curved in Figure 38, shall only be used when the profile is not composed of circular arcs. The more coordinates specified, the better the uniformity of the curve.
112 112
12.9. Curved profiles composed of circular arcs should be dimensioned by radii, as illustrated
17
Dimensioning and tolerancing of size
in Figure 118.
Figure 118: The
dimensioning of a curved profile
Engineering drawing practice
Figure 37 – Dimensioning of a curved profile Figure 119: Linear coordinates of a series of points through which a profile es 119
Figure 38 – Linear coordinates of a series of points through which a profile es
Coordinates locating points on a curved surface, as illustrated in Figure 119, should
1.11 Dimensioning of keyways
only be used when the profile is not composed of circular arcs. The more coordinates
specified, the uniformity Keyways in hubs or shafts shallthe bebetter dimensioned by oneofofthe thecurve. methods shown in Figure 39. NOTE: Further information on keys and keyways is given in BS 4235-1, Specification for metric keys and keyways – Part 1: Figure 120 illustrates a method specifying a cam in association with a Parallel and taper keys and BS 4235-2, Specification for metricof keys and keyways – Partprofile 2: Woodruff keys and keyways.
follower. The follower is indicated by a long-dashed double-dotted narrow line type 05.1.1 (see Table 1).
Figure 120: Specifying dimensions in association with a follower
0˚
b
shown in Figure 5. NOTE Further information on keys and keyways is given in BS 4235-1, Specification for metric keys and keyways – Part 1: Parallel and taper keys, and BS 4235-2, Specification for metric keys and keyways – Part 2: Woodruff keys and keyways. The Essential Guide to Technical Product Specification: Engineering Drawing
18
Figure 5
Dimensioning of keyways
a) Parallel hub
d) Parallel shaft
f) Parallel shaft
b) Tapered keyway in parallel hub
c) Parallel keyway in tapered hub
e) Parallel keyway in tapered shaft
g) Tapered shaft
Figure 39 – Dimensioning of keyways
1.12 Tolerancing
© BSI 2006 •
21
Tolerancing is the practice of specifying the upper and lower limit for any permissible variation in the finished manufactured size of a feature. The difference between these limits is known as the tolerance for that dimension. All dimensions (except auxiliary dimensions) are subject to tolerances. Tolerances shall be specified for all dimensions that affect the functioning or interchange ability of the part. Tolerances shall also be used to indicate where unusually wide variations are permissible. Tolerances shall be applied either to individual dimensions or by a general note giving uniform or graded tolerances to classes of dimensions, for example: TOLERANCE UNLESS OTHERWISE STATED LINEAR ±0,4 ANGULAR ±0° 30’ The method shown in Figure 40a should be followed where it is required to tolerance individual linear dimensions. This method directly specifies both the limits of the size of the dimension, the tolerance being the difference between the limits of the size. The larger limit of the size shall be placed above the smaller limit and both shall be given to the same number of decimal places. The method shown in Figure 40b can be used as an alternative way of specifying tolerances.
6.9.3 Tolerancing of individual linear dimensions The method shown in Figure 85 is recommended where it is required to tolerance indi-
Dimensioning andThis tolerancing size specifies both the limits of the size of the6. Dimensioning of technical 19 vidual linear dimensions. method of directly drawin dimension, the tolerance being the difference between the limits of the size.
32,15 31,80
nce by
32
+0,15 -0,20
f size
The larger limit of the size is placed above the smaller limit, and both are given to the
a) places. same number of decimal
b)
Figure 40 – Linear dimension tolerance by directly specifying limits of size 6.9.4 Tolerancing of individual angular dimensions The methods shown41 in Figure 86used may be to tolerance individual angular dimensions. The methods shown in Figure may be to used tolerance individual angular dimensions.
Figure 86: Tolerancing
30 30' 30 0'
(a)
(b)
a)
0 30,5 ± 0,1
90 ± 0 30'
angular dimensions
(c)
b)
c)
Figure 41 – Tolerancing angular dimensions
6.10 Summary
1.13 Interpretations of limits ofparts size forstandards a feature-of-size This chapter has covered those of the that deal with dimensioning and
tolerancing which are likely to be of use to Design and Technology teachers and their Limits of size for an individual feature-of-size shall be interpreted according to the principles and rules students in schools and colleges. The key points are as follows. defined in BS ISO 8015, BS EN ISO 14660-1 and BS EN ISO 14660-2. A feature-of-size may consist of two parallel plane surfaces, a cylindrical surface or a spherical BIP 2155 File name: 2008-01133_40b.e ] The general principles dimensioning as set out in may BS 8888:2006 should always surface, in each case defined with a of linear size. A feature-of-size also consist of two plane surfaces at an angle to each other (aifwedge) a conical surface, in each defined with an angular be followed effectiveorcommunication between thecase designer, manufacturer and size. BS ISO 8015 states that limits of size control only the actual local sizes (two-point measurements) end is to be established and maintained. of a feature-of-size and not its deviations of form (e.g. the roundness and straightness deviations of a ] Functional dimensions are those that directly affect the function of the product. cylindrical feature, or the flatness deviations of two parallel plane surfaces). Form deviations may be ] All dimensions except auxiliary dimensions are subject to tolerancing. controlled by individually specified geometrical tolerances, general geometrical tolerances or through ] envelope The decimal marker is represented by a comma not a point. the use of the requirement (where the maximum material limit of size defines an envelope of perfect form]forGroups the relevant surfaces; seeleft BS and ISO right 8015). of numerals to the of the decimal marker should be divided BS ISO 8015 defines the principle of independency, according to which specified up into groups of three, counting from the decimal marker, and aeach full space, notdimensional a and geometrical requirement on a drawing is met independently, unless a particular relationship is comma, left between them. specified. A relationship may be specified through the use of the envelope requirement or material condition modifiers maximum material condition (MMC) or least material condition (LMC). Where no relationship is specified, any geometrical tolerance applied to the feature-of-size applies regardless of feature size, and the two requirements shall be treated as unrelated, as shown in Figure 42. Relevant standards Title The limits of size do not control the form, orientation, or the spatial relationship between, individual Technical drawings — Dimensioning and features-of-size.BS EN ISO 1660
Consequently, if a particular relationship of size and form, or size and location, or size and tolerancing of profiles orientation is required, it needs to be specified. BS ISO 129-1 Technical drawings — Indication of dimensions and tolerances — Part 1: General principles
BS 8888:2008
BritiSh Standard
20
The Essential Guide to Technical Product Specification: Engineering Drawing
25,0 24,9
Figure 3 Permissible interpretations when no form control is given on the drawing
a) drawing presentation
a
b
c
NOTE There is no form control (i.e. over roundness, straightness or cylindricity). Measurements a, b and c may lie between 25.0 mm and 24.9 mm, meeting the drawing requirement using two-point measurement only. b) Permissible interpretation: straightness unconstrained
Maximum size
5,0
2
Maximum roundness deviation (resulting from a lobed form)
NOTE For any cross-section of the cylinder, there is no roundness control. c) Permissible interpretation: roundness unconstrained
Figure 42 – Permissible interpretations when no form control is given on the drawing 15.1.2 Limits of size with mutual dependency of size and form COMMENTARY AND RECOMMENDATIONS ON 15.1.2
1.13.1 Limits of size with mutual dependency of size and form Some national standards apply, or have applied, the Envelope Requirement to all features-of-size by default. As the Envelope Requirement the default, they have not used a symbol by to Some national standards apply, or have applied, has the been envelope requirement to all features-of-size indicate this requirement; rather they use a note to indicate when this default. As the envelope requirement has been the default, they have not used a symbol to indicate this is not required. This system of tolerancing is sometimes described as the requirement; rather they use a note Principle to indicate when this is or notthe required. Thisofsystem of tolerancing of Dependency, application the Taylor Principle. is sometimes described as the principle of dependency, or the theEnvelope Taylor principle. Standards which apply, or application have applied,ofthe Requirement by Standards which apply, or have default applied, the envelope requirement by default include: include: ASME Y14.5 (the requirement that there is an envelope of perfect form corresponding to the Maximum Material Size of the feature is The requirement that there shall be an envelope perfect defined asofRule #1). form corresponding to the maximum
ASME Y14.5
material size of the feature is defined asBS Rule 308#1). (the Principle of Dependency was taken as the default option under BS 308, although the option of working to the Principle of Independency was included, through the use of The principle of dependency was taken as the optionI indication): under BS 308, although the option of working the BSdefault 308 triangle
BS 308
I
8888 to the principle of independency was included, through the use of theBS BS 308 triangle I indication.
BS 8888 prior to the 2004 revision (the Principle of Dependency was I taken option under BS 8888:2000 and BS 8888:2002, BS as 8888the default although the option of working to the Principle of Independency was included, through the use of the BS 8888 triangle I indication).
16 • © BSI 2008
21
Dimensioning and tolerancing of size
BS 8888 Prior to the 2004 revision; the principle of dependency was taken as the default option under BS 8888:2000 and BS 8888:2002, although the option of working to the principle of independency was included, through the use of the BS 8888 triangle I indication.
BS 8888:2004 and BS 8888:2006 the principle of dependency could be explicitly invoked through the use of the BS 8888 triangle D indication. BS 8888
D
As the interaction between the envelope requirement and individual geometrical tolerances is not always fully defined within the ISO system, and as the application of the envelope requirement by default to all features-of-size is not formally ed within the ISO system, the use of the principle of dependency is no longer recommended.
1.14 Datum surfaces and functional requirements Functional dimensions shall be expressed directly on the drawing, as shown in Figure 1. The application of this principle will result in the selection of reference features on the basis of the function of the product and the method of locating it in any assembly of which it may form a part. If any reference feature other than one based on the function of the product is used, finer tolerances will be necessary to meet the functional requirement, which in turn will increase the cost of producing the product, as shown in Figure 43 on page 22.
1.15 Relevant standards BS EN ISO 1660, Technical drawings — Dimensioning and tolerancing of profiles BS ISO 129-1, Technical drawings — Indication of dimensions and tolerances — Part 1: General principles BS ISO 3040, Technical drawings — Dimensioning and tolerancing — Cones BS ISO 10579, Technical drawings — Dimensioning and tolerancing — Non-rigid parts BS ISO 406, Technical drawings — Tolerancing of linear and angular dimensions BS EN 22768-1, General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications BS 4235-1, Specification for metric keys and keyways — Part 1: Parallel and taper keys BS 4235-2, Specification for metric keys and keyways — Part 2: Woodruff keys and keyways BS ISO 8015, Technical drawings — Fundamental tolerancing principle BS EN ISO 14660-1, Geometrical Product Specifications (GPS) — Geometrical features — Part 1: General and definitions BS EN ISO 14660-2, Geometrical Product Specifications (GPS) — Geometrical features — Part 2: Extracted median line of a cylinder and a cone, extracted median surface, local size of an extracted feature PP 8888-2, Engineering drawing practice: a guide for further and higher education to BS 8888:2006, Technical product specification (TPS)
A
22
The Essential Guide to Technical Product Specification: Engineering Drawing
Description
Drawing
1
2
12,00 11,92
Date: 15/06/2009 Approval of issue 6,05 6,00
5,5 5,0
NOTE: One direct dimension with a tolerance of 0.05 mm is needed to satisfy the condition shown in a). A nominal flange thickness of 5 mm has been assumed. This value is non-functional and can have BIPany 2155 large tolerance.
Modifications:
File name: 2008-01133_43a.eps
correct functional reference surface
d) Item 2 dimensioned from a nonfunctional reference surface
File name: 2008-01133_43b.eps
BSI/PM: Jenny Cranwell Date: 15/06/2009
BIP 2155
11,03 11,00
5,00 4,98
NOTE: Tolerances have had to be reduced; two dimensions with tolerances of, say, 0.02 mm for the flange and 0.03 mm are now needed to satisfy the condition shown in a).
incorrect non-functional reference surface
Figure 43 – Effect on tolerances by changing datum surfaces from those determined by functional requirements
BIP 2155
Date: 15/06/2009 Modifications:
c) Item 2 dimensioned from a functional reference surface
18,00 17,97
b) Detail of head of item 1 showing given limits of size, with a tolerance of 0.03 mm
Modifications:
3
BSI/PM: Jenny Cranwell Approval of issue
a) Assembly drawing showing a given functional requirement, namely the limits of height of the top face of item 1 above the top face of item 3, with a tolerance of 0.08 mm
File name: 2008-01133_43c.eps
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