Knowing your calipers

[LRRPF52]

I just wanted to introduce the topic of the calipers with a diagram of the calipers and some of their features.

[LRRPF52]

[JASmith]

Nice description!

[sneaky one]

Sweet find! This should help a few out.

[wheelguner]

I use to help the Quality Assurance Department of an aerospace company by preparing visual aids similar to that as well as lessons and tests for their personnel. That is great stuff. I was able to sit in am classes when I wanted to. One of lessons was to teach us to be consistent in our operation of various measuring devises such as calipers. One of the tests was to measure an assortment of shims marked with alphabetical characters and to list the readings we got. One of the perks of my job was to get a set of "Standard units" they used to test instruments. In it was a precision gauge that was 1"x.50"x.25" (accurate to +/-.0001) and a OIML Class E2 stainless steel 10 milligram calibration weight ( has an accuracy of +/- 0.008 milligrams (0.000008 grams) both in airtight containers and to be handled only when wearing gloves. Nice to have and damned glad that I didn't have to pay for them.
In case you haven't already figured out from this and my other posts on this forum I AM ANAL and I have a teeshirt that says that the front with */-.0000005 below those words.

[1075 tech]

I only have a set of electronic calipers. I've never used the dial ones. I find that the amount of tension or pressure used when measuring can change the results by several thousandths. How does one know exactly how much pressure to apply to get consistent readings?

[LR1955]

I only have a set of electronic calipers. I've never used the dial ones. I find that the amount of tension or pressure used when measuring can change the results by several thousandths. How does one know exactly how much pressure to apply to get consistent readings?

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

[65Whelen]

I'll add my two cents here. I worked QA that had to comply with milspecs and medical devices manf., both demanded certified, traceable calibration of all measuring devices. Is this necessary for a lot of the discussion here, no. But if you have a question about the accuracy of your calipers, it's easy to find out. I picked up a set of gauge blocks used for calibration at a garage sale. Or, stop at reputable machine shop, odds are they have a set gauge blocks and ask them to check your calipers.

[LRRPF52]

I'm interested to hear what some of you with industry standardization experience have to contribute, as well as those like LR1955 who have been reloading for decades.

One rule of thumb is to always zero out your calipers before taking a measurement. This involves:

1. Wiping the caliper jaws clean,

2. Closing the jaws to mechanical zero,

3. Confirming that the gauge indicates "0".

[1075 tech]

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

Yeah sorry. I guess it was 10/1000's. I'm guessing if I have to worry about measurements varying by, say, 0.0005", I'm too anal or there is a serious issue.

[LR1955]

I'm interested to hear what some of you with industry standardization experience have to contribute, as well as those like LR1955 who have been reloading for decades.

One rule of thumb is to always zero out your calipers before taking a measurement. This involves:

1. Wiping the caliper jaws clean,

2. Closing the jaws to mechanical zero,

3. Confirming that the gauge indicates "0".

Absolutely correct.

Every time I reload I do that check list. Amazing how many times the calipers have slipped and are way off before zeroing. Or some crud has gotten between the jaws and is giving false readings.

I am not particularly anal about slight variances due to pressure on the calipers when I measure something but damn sure will clean them and zero them before using them.

LR55

[JASmith]

I try to use the same pressure I used to get "0" when taking serious measurements.

[Djgrendel]

One thing many people overlook is checking calipers over a standard to verify zero means zero and 1" means 1" and so forth.

[rocksoldier1]

A good set of 1-2-3 blocks might be cheaper than individual standards.

[Adam Lilja]

Just saw this. I find digital calipers to be worthless (especially is working with and around liquids) and much prefer a good set of dial calipers. Starrett or Mitutoyo are the best. Brown and Sharpe 3rd. You will never get as good a reading with calipers as you will with a micrometer, whether it be inside mic or outside mic. Calipers are usually a ballpark measurement tool. By ballpark I mean +-.002

[rabiddawg]

I find digital calipers to be worthless By ballpark I mean +-.002

I can live with that but I am glad to hear my barrel maker can't!

[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...

[Klem]

Consistent dialling.
Never seen them on calipers but on micrometers they often come with a secondary spring loaded dial that acts like a torque wrench. You spin the dial closing the jaws until it comes up against the object you are measuring and then the secondary ratchet click over at the same torque each time. Called a ratchet screw, friction dial or ratchet dial.


I've never really needed the extra precision that a micrometer gives you over a set of calipers. Calipers do 99% of all the measuring I ever do when reloading.

[explorecaves]

I'm interested to hear what some of you with industry standardization experience have to contribute, as well as those like LR1955 who have been reloading for decades.

One rule of thumb is to always zero out your calipers before taking a measurement. This involves:

1. Wiping the caliper jaws clean,

2. Closing the jaws to mechanical zero,

3. Confirming that the gauge indicates "0".

4. Take your measurement 2-3 times

5. close jaws to mechanical zero

6. confirm zero was maintained (too much pressure while measuring will cause the zero to drift)

[wraith1516]

Does any one know of any where to have a set of digital calipers repaired i have a mititoyo calipers that have a issue with draining the battery and won't read anything over 3 inches without giving an error or am I just out $275