Knowing your calipers

[The Profit Joseph Sith]

1075:

For reloading it won't make a difference. Just use a consistent amount of pressure each time if you think it matters.

I do hear you though about changes depending on how much pressure you put on the calipers. Sure will give different measures. Never seen it go as far as several thousandths though. Maybe a thousandth? Anyway, it doesn't matter when measuring for handloading.

LR1955

What's a caliper?

When i was a kid i used dial calipers (mititoyo) and for some reason got a kick out of measuring my hairs (not the short ones) i think this would be a good way to practice tension because you can crush it somewhat easily but would still have to kinda try. Technically there are very specialized ways to measure soft things precisely lime rubber or foam. Anyway you shouldn't see more than about .0005" deviation in pressure. Or there is dirt in the gear track or pickup is dirty or cheap calipers? I have used tons of certified mesuring tools at boeing and have mititoyo dig o matics and a couple pairs of autozone digital calipers as well. The cheap ones are actually pretty decent...

What i have issues with is the micrometers.. its easy to over torque a threaded screw measuring system. Especially the older ones without any kind of ratchet tensioner. There again i find a hair of some sort is good for practice. They Should measure about .0015-.002" depending on how thick your hairs are..

EDIT Mr. Lilja is indeed correct if I remember correctly even the certified digital calipers @ boeing are certified to -/+ whatever. nothing is ever exact... And i agree i kinda prefer dial over digital its amazing how much more info you get from them. But I do like my digitals more for what i do. And they are very reliable if good quality. And also 2nded jf you ARE trying to use your calipers for to measure .000x" you should definitely use micrometers.

All that said boeing uses nothing but digital everything now. And their gauges are VERY accurate. Its easier to have fewer moving parts with digital. I used $20k torque wrenches that had no moving parts but meaured strain in the head and plug into your laptop to record torque values. Wich you can just upload into velocity program to sell your jobs.
My last boss had digital mics that would read out to .00000x" not sure of their accuracy though. Not really ever needed if you ask me. That's getting into ic chip circuitry size territory... Which would be measured optically...