calipers

[agd1953]

I have noticed when measuring case length etc that my calipers read a little different depending on how loose or tight you hold the jaws on the item being measured. I can vary by .003 or more. How do I get consistent measurements? I make sure the caliper zero is correct prior to measuring. Is it me or the calipers? Are electronic ones easier to use or more consistent? I don't want to over trim the cases.

 

[The Bushmaster]

adg1953...Stop forcing those calipers. Just move the calipers until the jaw faces touch the case or just when they come to a stop. No farther pressure is necessary and if forced will give you a bad reading. Using micromerers, calipers and other fine measuring devises are a learned skill, but not difficult to master. It's all in the touch. Just close the calipers down on the case or whatever you are measuring until the jaws stop and read the dial. Don't push any farther.

 

[agd1953]

thanks Bushmaster

 

[The Bushmaster]

Absolutely "No Problem"... What you were seeing when you applied more pressure was caliper flex. Practice on a shell case until you get the same reading repeatedly. Then you will have it...

 

[Clark]

With practice, you may be able to measure any pin gauge and determine it's size to the nearest .001"

If you get really tricky with a dial caliper, you may be able to tell if it is a "+" or "-" gauge, that is +.0001" or a - .0001". That trick requires everything to be done right:
1) Calibrate [screw on the dial face ] the calipers with a pin gauge very near the size to be measured.
2) Wipe off the jaws
3) Get the jaws square on the gauge to be tested.
4) Get the test object at the same location on the jaws.
5) Use the same force as during the calibration.
6) Find the spot and the force of greatest repeatability
7) Not every $20 Chinese dial caliper is capable of this, but some are.
8) Don't drop the calipers.
9) Get good by using your dial calipers for competing with machinists with their micrometers.

I buy + pin gauges:
up to 1/4"
http://www.use-enco.com/CGI/INSRIT?PMAKA=890-9739&PMPXNO=5215207&PARTPG=INLMK3
1/4" to 1/2"
http://www.use-enco.com/CGI/INSRIT?PMAKA=616-8130&PMPXNO=5215208&PARTPG=INLMK3

These are actually handy in handloading.
Placed in a collet bullet puller in a single stage press, they can be used as a powder compressor or as a neck mandrel, or as a primer pocket go or no-go gauge.

 

[wheezengeezer]

many calipers will get a different reading at the base of the jaws than at the tip of the jaws.good calipers can be adjusted.