Mauser Caliper Graduations.

[carl blum]

Hi Gang: Someone in the Unimat Lathe group has a Mauser Caliper and wanted to know how to read it. The front was easy enough, the top scale read to 1/64" and the bottom scale read to 0.01mm. The mystery was on the back, there is this odd progression of numbers and lines about every 3mm. It runs like this: 0, 0.005, 0.024, 0.055, 0.098, 0.154, 0.222, 0.0302, 0.395, 0.499, 0.617, 0.746, 0.888, 1.042 and it goes on. A friend said they form a geometric progression whose formula is x = 0.006194 n² - 0.003 where n are positive integers. But we still don't know what the scale can measure. It doesn't seem to be area of a circle. Any ideas?


Thanks, Carl.

[12L14]

Are there any inscriptions beside those numbers?
For example something like this:

[mklotz]

Some SWAGs...

A curve fitting the numbers on the back to the integers isn't terribly useful. The curve should be fit to the corresponding lengths of one of the caliper's scales (most likely the metric lengths).

The inscription in 12L14's picture begins "Gewicht in gr..." which translates to "Weight in grams...". The rest is unreadable. (A readable picture of the complete inscription would be helpful as would a comparison of the numbers on the back of both calipers.) My guess would be something like "weight in grams of a (TBD shape) made of (TBD material) with a dimension as shown on the caliper".

[12L14]

It's best photo I found, and my german - even quarter century ago - wasn't too good, but there is that part „Spez. Gew. 7,85”.
IIRC term You use for density is something like „specifik mas”, and 7,85 grams is really close to weight of cubic centimetre of „typical” carbon steel(that is 7,845 to 7,86 kilograms per litre).

[mklotz]

OTOH, the formula for the area of a circle is pi/4 times the square of the diameter and, suspiciously, pi/4 = 0.7854

If the number on the back scale was the square of the diameter read with the caliper then multiplying the back number by 0.785 would provide the area and the area would be simply related to a standard length to provide volume. An example will help my clumsy attempt to express my thinking in prose...

Suppose the back number represents in mm² the square of the caliper measurement. Then multiplying that by 7.85 ( 0.7854 * 10 mm = 1 cm)) would give the volume per centimeter of the cylindrical wire being measured.

If one then had a table of specific weights of various metals, expressed in terms of gm/cm³, it would be easy to calculate the weight of a long length of wire.

Admittedly, just another SWAG :-)

[12L14]

What is SWAG(I only know swage/swaging die)?

I'm looking for my old and trusty(or rusty - if I again leave it beside mill...) HP to calculate what You describe

[mklotz]

What is SWAG(I only know swage/swaging die)?

I'm looking for my old and trusty(or rusty - if I again leave it beside mill...) HP to calculate what You describe

SWAG = Scientific Wild Ass Guess

When you encounter unknown acronyms, this acronym finder...

https://www.acronymfinder.com/

can be a big help.

[12L14]

Thanks.

ps. 1018 density is circa 7.87 g/cm3 or 0.284 lb/in3 (for good start for someone else to calculate - not that I'm throwing towel).