Micro Meters 1a6r65

Micrometers DIN Standards and some historical background

Micrometer History Micrometer: Instrument permitting the measurement with great precision of various lengths, or very small angles (Micro + Meter) (French dictionary "Larousse") Micro: 1. Small 2. one millionth of 3. f. Greek (Mikros small) (The Oxford dictionary) Micron: one millionth of a meter The first measuring tool of this type was patented by the French inventor Mr Jean Laurent Palmer in 1848 as "calibre a vis et a vernier circulaire" (Screw caliper with a circular vernier). Today in 2001 we continue to manufacture external micrometers with these typical features.

The introduction of the micrometer to the mechanical world came about by the visit of the two American Engineers Mr Joseph R.Brown and Mr Lucian Sharpe to the Paris exhibition in 1867. At that time, their attention was called to Mr Palmer's invention, which greatly interested them. After some improvements of the Palmer design,the product was manufactured on a large scale and marketed successfully by the two partners. Here are some fine pictures of a Changeable Anvils Micrometrer from the well known AngloAmerican manufacturer "STARRETT" (many thanks to Kris Harrison from Te Anau)

 

As above in 1941 TESA developed and manufactured its first micrometer the "Minmetal" It was the first in a long line of instruments for quality control, that would contribute to the worldwide success of the Swiss company.

 

 

The good old "meaty" micrometer from PREISSER . Large heat insulator, the ratchet is located on the thimble (diam. 24,5mm) with easy access. One hundred graduation around the thimble! One revolution = 1,0mm / each graduation = 0,01mm can't go wrong with that. Also note the locking "wing nut" and the 8,0mm measuring spindle... what a change from the standard 6,5mm diam. spindle found in the market today! Lacquer paint finish. This type of micrometer can still be supplied today.

 

The more than famous SWISS TESA MASTER (and rightly called so...) Parallax-free reading of the thousand of millimeters (microns) on the thimble / The "tenths" of millimeters are being displayed by digital figures on a mechanical counter. (it goes "click" "click" when being rotated) Very fine instruments for the purist. Still available today up to 300mm !

DIN 863 STANDARD FOR MICROMETERS DIN: Deutsche Industrie Normen (German Industrial Norms) The directives for the inspection and testing of Micrometers can be found in the German Industrial Norms DIN 863. I thought some of you would appreciate some facts and figures...

 

The micrometers ratchet is set to give a measuring force of 0.5 - 1.0 daN. However, the ratchet can only fulfill its function if the spindle is moved against the work piece. Then only a measurement can be taken, this without force. It will also achieve accurate and consistent readings. The extensive practice of NOT using the ratchet for measurements against a work piece is false! The reference temperature is 20º C (= 68 F) and this should be observed in order to measure accurately. The Micrometer and its possible errors: a) Lack of flatness of the measuring faces b) Lack of parallelism of the measuring faces c) Inaccurate setting of the zero reading d) Inaccurate readings following the zero position e) Inaccurate readings shown by the fractional divisions on the thimble Inaccurate readings from zero onwards are generally found to be caused by pitch errors in the screw. This is a problem I have seen many times with low quality micrometers. Pitch errors are being termed as "the progressive error" and "the periodic error" The progressive error: exists when the pitch of a screw is uniform, but either exceeds or is less than the nominal figure. The periodic error: is that which recurs at regular intervals. It varies in magnitude when measured form thread to thread along the screw. Both progressive and periodic errors can be determined by using block gauges

One of the first TESA Swiss Made Digital micrometer. The "in" features of these days was the conversion "Metric - Inches" / "Zero in" function (floating zero) / a LCD display with coloured segments allowing the classification of measured values.... / RS 232 output and ABS feature (sorry no Air Bags..... yet!)

The latest TESA Swiss Made digital micrometer. How's that for technological improvement? To be noted the unique feature of a 30 mm travel range I have no comments to make beside the fact, it is water/coolant spray protection (Still... NO "Air Bags" for when you drop them on the workshop floor!)

Mould and Die making, combined with Micro-mechanics and electronics.Definitely Swiss! engineering excellence at it's best...

  Think BIG! Naval / Defence / Hydro Industry, Gas and Nuclear Power plants. Thermal plant turbines etc...Doesn't quite fit into my tool box!

And to conclude this page, I should not forget that Internal Micrometers also do play an important part in the industry.I personally think that one of the most important advance in the effective readings of internal measurements was with the fantastic invention of 3 Point Internal Micrometers. 3 Point Internal micrometers can be used for internal readings of Blind holes / counter bores / Trough holes / Deep holes measurements (with extensions and self centering devices)