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Esset_89 t1_j92f3p1 wrote

Reply to comment by ExHempKnight in "The longest-lived micrometer than can be bought." J.T. Slocomb micrometers and stand, all fully restored by myself. Each mic is between 70-120 years old, and they're all still accurate. by ExHempKnight

Bring the gauges as well, they also need to be checked

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ExHempKnight OP t1_j92ktrj wrote

Nah, once the standards are known, I can calibrate the mics myself. I'm not looking for NIST traceability.

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nicaldrogo t1_j92ymiy wrote

Depending on usage, you might need to get them tested for flatness and linearity. Parallelism for a 0 to 1 inch mic as well

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ExHempKnight OP t1_j938jxk wrote

I'd love to have them all lapped, but that's beyond any equipment I have, and prohibitively expensive to have done.

There aren't a lot of places that can do it, anyway.

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nicaldrogo t1_j93lqd1 wrote

I think you misunderstood me. You mentioned that you could use the end standards to calibrate the mics. All that does is set the zero on the mic itself. Calibrating a mic consists of checking for linearity, flatness, and parallelism. Like you mentioned, it won't matter for your use.

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ExHempKnight OP t1_j942yaa wrote

Fair points. If I understand correctly, the measuring faces are checked using a set of optical flats, each a slightly different length, to check for parallelism at different rotational positions of the spindle, right?

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Tawmcruize t1_j95t1i1 wrote

As a quality tech who calibrates micrometers often, if you have any that seem to not center very well ( you get a measurement but a little more force changes it by a tenth or so) you more than likely have a burr or foreign material on edge of the faces and a really smooth stone should be able to take it off, this is what I think I used for a v mic that had rust on the carbide faces and it checks gauge pins to tenths still.

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