"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.ExHempKnight OP t1_j91sxsw wrote
Reply to comment by CR123CR123CR 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
Thank you! I need to bring the standards to an instrument calibration place, and have them checked. I'm sure they're fine for my little hobby shop, but I'm kinda particular about that stuff.
tlove01 t1_j926wwg wrote
Metrology is cool
ExHempKnight OP t1_j92o92l wrote
It really is. Since I've started this journey of precision work, I've really gained an appreciation for how important the tiniest of distances really are. And that everything is rubber.
agnarxrist t1_j939305 wrote
What do you mean by “everything is rubber”?
ExHempKnight OP t1_j93adnm wrote
Everything is flexible, to some degree. Drop a feather onto a pool table, and the weight of that feather will bend the slate of the pool table. It's a tiny, tiny, TINY amount, but given appropriately sensitive equipment, you will find that there's a deflection.
When you're measuring down to 3, 4, or especially 5 decimal places, even the heat of your breath can distort a part a measureable amount.
Robin Renzetti has a great demonstration of this, if you're curious. Skip to 31:00 for the relevant part.
phuntism t1_j93g2qp wrote
For those who watch the video: If you skip to 31:00, you need to watch to 35:49, to see why he's doing this testing on his carpet? :)
zyzzogeton t1_j93of6q wrote
Adam Savage has some interesting discussions about his journey towards precision. Pask has a similar kind of arc as well on his channel. The hallmark of craftsmen is that their tastes become more and more exacting over time. The tools needed to accomplish that become more and more specialized and beautiful too.
ExHempKnight OP t1_j93wnid wrote
I've enjoyed Adam Savage's journey. Wild to see someone I admire so much, have the same kinds of struggles and learning experiences that I have.
Occhrome t1_j92af4m wrote
I’m sure they will be fine. We calibrate our sensitive torque wrenches all the time and they hardly ever need adjustment.
ExHempKnight OP t1_j92m00q wrote
I'm sure they will, as well. But as old as they are, I'm sure they're a bit worn. I don't need them to be exact, I mostly need to know exactly how off they are, so I can compensate when I calibrate the mics.
THE_CENTURION t1_j92q9rn wrote
I mean... That's a completely different kind of tool I don't know why you think that's applicable.
These kinds of standards can corrode and change or need to be re-lapped, or just wear. That doesn't ruin them, but you need to know how long they actually are so you can zero the micrometer correctly.
avidblinker t1_j9335mn wrote
Nah they’re right. I calibrate the color on my computer’s LCD display at home every few months and typically don’t need to change much
Lampshader t1_j93bdpu wrote
Nah that can't be right, because I have to reset the clock on my microwave every month
The_Best_Dakota t1_j93hrak wrote
That’s just the power company being shit
Lampshader t1_j93ijx3 wrote
It almost certainly has its own internal clock rather than using the mains frequency, but that's beside the point
The_Best_Dakota t1_j93irt9 wrote
I was making a joke about the power going out and needing to reset it bc I find myself having to do that at a frequency that’s probably more consistent than that of the power itself
Lampshader t1_j94b0an wrote
Ah oh right, yeah that's annoying too
Fat_Head_Carl t1_j93m644 wrote
With all that work you put in, why the fuck not!
I have inherited a box of machinist tools... I'm not sure what they're good for, but they seem all new. They're starett
Esset_89 t1_j92f3p1 wrote
Bring the gauges as well, they also need to be checked
ExHempKnight OP t1_j92ktrj wrote
Nah, once the standards are known, I can calibrate the mics myself. I'm not looking for NIST traceability.
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
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.
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.
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?
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.
boonepii t1_j95p3uq wrote
I got to see a huge metrology operation last week. Over 150 calibration and repair technicians. Was very very cool.
Metrology is a very cool job. Tons of demand.
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