My caliper......junk or normal???

[shoot'n hogs]

I have a mechanical stainless steel caliper.  This will be difficult to explain but here goes.  When you open it up to measure a casing, the tips of the jaws (flat part, not the edged section)  measure different from the part closest to the body.  The same goes for the middle of the jaw.  The caliper is new from cabelas.  When the jaws are closed, they appear to be flush.  Is this normal?  Where should I take the measurement from?  Any help would be nice.  Thanks!

[John Traveler]

I used to work in a metrology (instrument calibration) shop.

I'll bet that your readings are not consistent from one measurement to another either.

The problem you describe is common.

You need to dissable and clean the pinion gear and rack that it rides in.

Dirt particles cause the dial indicator to jump around and give bad readings.

HTH
John

[Questor]

It doesn't sound right to me. I have two calipers, one cheap RCBS plastic dial caliper and one RCBS digital and they both measure uniformly regardless of where the case is gripped between the jaws.

[Duffy]

I have a cheap china pair and while they are pretty accurate there is a difference between the knifed tips and the flat section near the frame you speak of. I belive it's about .003 or so on mine. As long as you know of this and take all your measurements the same no biggie. Also make sure you are holding the case flat in the jaw's. It's very easy to get things a bit cocked and not notice it. I usually roll the case between my fingers gently until you feel it seat against the jaws. Many times the mouth isn't square either and you'll get high spots.

Ryan