Four Facet Drill Grinding Jig 5q1l4y

Four Facet Drill Grinding Jig - Construction Notes This drill grinding jig is based on a design published in Model Engineer magazine in the mid1990s. I do not have a copy of the magazine, but I made some notes from the original article. I made a number of changes to the design as originally published to make the jig easier to use on my grinder. The notes below, and the associated drawings, are compiled from my sketches in my notebook and measurements taken from the jig I made. Throughout these notes reference is made to brazed construction. I MIG welded my unit together, each t held by a few tack welds rather than a complete unbroken bead on the seam. It doesn’t look as pretty, but it works just as well. No dimensions are critical except those that determine the grinding angles, and the cross holes in the four guide blocks (parts 20) which take the drill to be sharpened – these holes must be on the centreline of the blocks, or the symmetry of the drill point will suffer. When matching the jig to a particular grinder it may be necessary to change the height of the Main Body (part 6) to ensure the drill point is at approximately the same height as the grinding wheel centre. Similarly, the ‘reach’ of the body (dimensioned as 35mm on the drawing) was necessary to clear the base of my bench grinder – this may need to be changed to match the grinder that the jig is being fitted to. All sheet metal parts are made from 2mm thick material. Again, this dimension is not critical, but if changed, the appropriate changes may be made to the relevant dimensions on parts 4, 10 etc. for cosmetic reasons. For most parts the materials are not critical – I recall that in the original article the drill was made of aluminium and the various knurled screws were made of brass. Two alternative constructions are shown for the drill end-stop. The original article described a component fabricated from sheet (parts 13-16). I made the stop from a solid block (part 22) secured by a screw (part 23). The M3 x 0.5 threaded hole in the feed stop bush (part 8) was intended to take a grub screw and a nylon or copper pad to act on the feed stop (part 9) to prevent it changing setting due to vibration. I cut the M6 x 1 thread on the feed stop with a split die adjusted to cut the thread a little large so it is a firm fit in the bush – further anti-vibration precautions proved to be unnecessary and the grub screw and pad were never fitted.

The pivot stud hole in parts 1, 2 and 3 is initially drilled 2mm. After the parts are brazed together with the pilot holes aligned, the hole through all three parts is opened out to 3.3mm and tapped M4 x 0.7 When the pivot stud hole has been tapped, a short length of M4 studding (a bolt with the head cut off) is brazed into the tapped hole – the spelter being fed in from the part 1 side to prevent it flowing into the thread that will take the nut/locknut.

Four guide blocks (parts 20) are specified, each with a different size cross hole. The cross hole takes the drill to be sharpened and each block covers a range of 1mm in diameter (e.g. the 3mm hole covers drills from 2-3mm dia. Etc.). Although four guide block screws (parts 21) are specified, only one is needed in reality as the same screw can be fitted to which ever block is in use. Ian Newman [email protected]

Four Facet Drill Grinding Jig – Instruction For Use

Installation The 8mm bar that forms the top of the base body must be at 90 degrees to the grinding wheel surface. Position the base body so that when the feed stop is fully unscrewed the main body is just clear of the grinding wheel surface. Check this in both the 10 degree grinding position and the 30 degree position. Check the location of the jig. Read the section on Using The Jig (below) and put a few drills of various sizes in the machine to check that there is enough movement to allow the unit to operate – if you use a bench grinder you will find things are a bit tight under and around the grinding wheel and some wood blocks will probably be needed to bring everything to the right height. Secure the jig to the bench.

Using the Jig 1)

Using the smallest guide block that will fit the drill, place a guide block on the drill body at the base of the flutes.

2)

Looking onto the point of the drill, rotate the drill until the line of the cutting edges (the lips) are at 90 degrees to the long axis of the guide block – see diagram below.

For small drills a loupe or other magnifier is a help here. As the drill is ground back, the line of the lips rotates in a clockwise direction (down the helix of the flutes) so this position may need to be reset if you are grinding back a particularly blunt drill.

Page 1

Four Facet Drill Grinding Jig – Instruction For Use

3)

Set the grinding jig in the 30 degree position (with the angle setting lock screw located in the lower locking guide). Place the rocker vee at the bottom of the main body over the rocker bar that forms the top of the base body and adjust the feed stop so the jig is 2-3mm clear of the grinding wheel surface.

4)

Place the drill in the drill groove and adjust the drill end-stop until the drill is just touching the grinding wheel.

5)

Press the drill clamp down to hold the drill in place, check that everything is clear of the grinding wheel then start the grinder. Holding the drill clamp firmly against the drill and pushing the rocker vee feed stop against the end of the rocker bar, rock the drill across the grinding surface (observing all the usual safety rules)

6)

Take the drill off the jig, rotate through 180 degrees and repeat to grind the other edge.

7)

Adjust the feed stop to take off a little more from the drill and repeat steps (5) and (6) until both sides of the drill have been ground to a smooth, uniform condition.

8)

Stop the wheel and reset the adjustable body to the 10 degree position.

9)

Using the feed screw adjust the position of the drill so it just touches the grinding wheel surface.

10) Start the grinder and repeat the grinding process to produce a thin 10 degree lip on each side of the drill.

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Four Facet Drill Grinding Jig – Parts List Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Description

Material

Dimensions

Qty

ADJUSTABLE BODY ANGLE SETTING PLATE PIVOT BLOCK ANGLE SETTING LOCK BUSH ANGLE SETTING LOCK MAIN BODY ROCKER FEED STOP BUSH FEED STOP ANGLE SETTING LOCK GUIDE DRILL DRILL CLAMP DRILL END-STOP PLATE DRILL END-STOP PLATE GUIDE DRILL END-STOP LOCK DRILL END-STOP LOCK NUT BASE BODY ROCKER BAR

MS MS MS MS MS MS MS MS MS MS MS Nylon MS MS MS MS MS Silver Steel

1 1 1 1 1 1 1 1 1 2 1 1 1 2 1 1 1 1

GUIDE BLOCK GUIDE BLOCK SCREW DRILL END-STOP BLOCK DRILL END-STOP LOCK SCREW

MS MS MS MS

4 4 1 1

PIVOT STUD PIVOT WASHER PIVOT NUT PIVOT LOCKNUT FEED STOP FRICTION PAD FEED STOP FRICTION SCREW DRILL SCREW DRILL CLAMP SCREW

MS MS MS MS Nylon MS MS

M4 M4 M4 M4

x 0.7 x 15 crinkle x 0.7 x 0.7

M3 x 0.5 grub M3 x 0.5 x 5 hex ∅3 x 12 self tap

1 1 1 1 1 1 2 2

M4 x 0.7

30 deg

dia 12

3

NOTE Drill dia 2 pilot hole only. Open to full size after assy.

7

15

30 deg

R7 2

21

3

5

15

dia 8 dia 6 M3 x 0.5

4

94

115

5

6 M3 x 0.5

dia 10

R 10

25

2

R6

M4 x 0.7

30 deg

NOTE Drill dia 2 pilot hole only. Open to full size after assy.

SCALE

A4

SIZE

Ian Newman [email protected]

1:1

dia 6

6

DWG NO

SHEET

1 of 2

FOUR FACET DRILL GRINDING JIG BODY

All parts MS unless stated

TITLE

12

50

2 4

6 80

20

1

20 16

115

20

92

4

7

1

REV

R6

9

dia 4

R6

6

6

35

R6

30 deg

30 deg

10 deg

10 deg

100

2 x 5 dia

R 80

R6

124

6

7

dia 5 dia 3

dia 6

12

9

8

dia 15

dia 4

SCALE

A4

SIZE

TITLE

Ian Newman [email protected]

1:1

80

dia 4

20 25

20 35 40

M6 x 1

dia 15 med knurl

10

dia 8

DWG NO

SHEET

2 of 2

M6 x 1

M3 x 0.5

FOUR FACET DRILL GRINDING JIG BODY

All parts MS unless stated

R2

2

10

1

REV

6.8

130

90 deg

30 deg

30 deg

13

28

36

M3 x 0.5

12

9

10 7

90 deg

10

18

36

SCALE

A4

SIZE

TITLE

Ian Newman [email protected]

1:1

Centres for 2 x self-tapping screws to fit slot in part 1

SHEET

DWG NO

1 of 1

FOUR FACET DRILL GRINDING JIG DRILL /CLAMP

All parts MS unless stated

Matl. Nylon

Shape to clear grinding wheel

16

11

30 12

4

1

REV

6

20

10

M3 x 0.5

R2

22 15 9

3

10

dia 3 CS

4

3

23

6

dia 8

6 dia 12

M3 x 0.5

14 4 2 4

12

M3 x 0.5

22

12

10

1.5

13

M3 x 0.5

15

16

15 SCALE

A4

SIZE

TITLE

dia 8

DWG NO

SHEET

1 of 1

1

REV

Braze part (15) to part (13)

DRILL END-STOP Ian Newman [email protected]

1:1

M3 x 0.5

dia 12

Rivet 2 x part (14) to part (13).

16

FOUR FACET DRILL GRINDING JIG

All parts MS unless stated

14

15

4

13

8

8

17

8

16

25

45

54

62

70

6 30

6

2

22

dia 8

SCALE

A4

SIZE

TITLE

Ian Newman [email protected]

1:1

70

DWG NO

SHEET

BASE

1 of 1

FOUR FACET DRILL GRINDING JIG

All parts MS unless stated

18

1

REV

30

12

M3 x 0.5

10

dia 3, 4, 5, 6

Part (20) Four required - one of each size cross hole.

20

22 18

dia 2

M3 x 0.5

dia 8 med Knurl

SCALE

A4

SIZE

TITLE

1:1

Ian Newman [email protected]

SHEET

DWG NO

GUIDE BLOCKS

1 of 1

FOUR FACET DRILL GRINDING JIG

All parts MS unless stated

21

1

1

REV

3

Pivot

1

2

1

3

4

2

SCALE

A4

SIZE

TITLE

1:1

DWG NO

SHEET

1 of 6

FOUR FACET DRILL GRINDING JIG ASSEMBLY Ian Newman [email protected]

All parts MS

Insert M4 studding to form pivot. Step braze from part (1) side.

Tap M4

After brazing, drill through pivot hole in (1) using hole in (2) and (3) as a guide.

Braze (1), (2), (3) and (4).

1

REV

Use wire to hold together parts (1), (2) and (3). Use jig to ensure 30 degs between parts (1) and (2).

11

Attach Drill Clamp (12) to Adjustable Body (1) using self-tapping screws into nylon body of (12). Drill Clamp (12) to be a free sliding fit.

SCALE

A4

SIZE

TITLE

1:1

SHEET

DWG NO

ASSEMBLY Ian Newman [email protected]

All parts MS

2 of 6

FOUR FACET DRILL GRINDING JIG

12

Bolt Drill (11) to Adjustable Body (1) using M4 bolts

1

1

REV

7

6 8

10

SCALE

A4

SIZE

TITLE

1:1

DWG NO

SHEET

3 of 6

FOUR FACET DRILL GRINDING JIG ASSEMBLY Ian Newman [email protected]

All parts MS

Braze Feed Stop Bush (8) to Rocker (7)

Braze 2 x Angle Setting Lock Guide (10) to Main Body (6)

Braze Rocker (7) to Main Body (6)

1

REV

5

Secure with crinkle washer, M4 nut and lock nut

SCALE

A4

SIZE

TITLE

1:1

DWG NO

SHEET

4 of 6

FOUR FACET DRILL GRINDING JIG ASSEMBLY Ian Newman [email protected]

All parts MS

1

REV

SCALE

A4

SIZE

TITLE

1:1

DWG NO

SHEET

5 of 6

FOUR FACET DRILL GRINDING JIG ASSEMBLY Ian Newman [email protected]

All parts MS

1

REV

SCALE

A4

SIZE

TITLE

1:1

DWG NO

SHEET

6 of 6

FOUR FACET DRILL GRINDING JIG ASSEMBLY Ian Newman [email protected]

All parts MS

1

REV

SCALE

A4

SIZE

TITLE

1:1

Ian Newman [email protected]

SHEET

DWG NO

1 of 2

FOUR FACET DRILL GRINDING JIG OPERATION - 30 degree grinding position

All parts MS

30 degree grinding position

1

REV

SCALE

A4

SIZE

TITLE

1:1

Ian Newman [email protected]

DWG NO

SHEET

1 of 2

FOUR FACET DRILL GRINDING JIG OPERATION - 30 degree grinding position

All parts MS

30 degree grinding position

1

REV

SCALE

A4

SIZE

TITLE

1:1

Ian Newman [email protected]

SHEET

DWG NO

2 of 2

1

REV

FOUR FACET DRILL GRINDING JIG OPERATION - 10 degree grinding position

All parts MS

10 degree grinding position

SCALE

A4

SIZE

TITLE

1:1

Ian Newman [email protected]

DWG NO

SHEET

2 of 2

1

REV

FOUR FACET DRILL GRINDING JIG OPERATION - 10 degree grinding position

All parts MS

10 degree grinding position