caliper vs micrometer

'Neck, I am a machinist by trade. Have Thousands of $ worth of precision measuring instrument and all I use are a quality set of Brown and Sharpe dial calipers for my reloading. As to the calibrating of calipers:
Resetting zero does not infact calibrate the calipers. Massair is correct in that the calipers use a geared rack and mics use ground threads. The calipers come from the factory with zero at the top of the dial. After time or missuse the gear on the dial will "jump" the teeth on the rack, thus causing the zero to move. Usually only quality equipment can be truely calibrated. My calipers have a slot on the back of the dial that you can insert a small object ( opened paper clip) into that will release the dial gear from the teeth on the rack. You then close the calipers with zero at the top and remove the paper clip. As with any often used tools measuring instruments should be calibrated yearly or if misshandled.

massair said:

bigsig said:

'Neck, I am a machinist by trade. ........

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Hey, if you are an "old-time" machinist, can you tell me HTH could my Dad (Tool & Die Maker, 1930s- 50s) possibly keep track of table position on, say, a Bridgeport mill? Big pad of paper and some kind of secret way of counting turns of the dials?

He never got to see/use digitals, poor guy. I put a set on my Bridgeport when I bought it, about 1990 in Phoenix, used, an old one, but gets my jobs done.

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Sorry massair I'm only 35 Have been machinist for 15 years. Now when I learned the trade we didn't use digital readouts, but all machines should have calibrated dial on them mine do. Now to put this into perspective I'll post a pic of me and my machine.
G]:x6b68wf6]http://i42.tinypic.com/sytsue.jpg[/IMG]

eddybo, this is a 120" BETTS boring mill, circa1958 I believe. I can swing 126", have about 96" under rail, and each of the rams have 80" of travel in Z. It turns at a whopping 35 rpms max and will feed between .005" and 1.0" per revolution. I have been running mills and verticle turret lathes most of my career. I can run a lathe, but prefer the VTL's. If you look at the upper right of the pic you will see a platform fastened to the right head. While machining the tops of these parts I actually ride up there so I can see in the bore and such. Can you imagine the size revolver cylinder I could make with this machine? Ha Ha :gatlin: :blol:

Starret, Browne & sharp, Mitutoyo= top of the line
SPI, Fowler= good
value= jjjjjjjjjjjunk
Try this out
http://www1.mscdirect.com/Dial-Calipers/Calipers/Measuring-Instruments/s1330.HTML

I use a set of "cheaper" fowler calipers to reload. All my good tools are at work. As long as your calipers read "0" with them all the way closed and there is no visible gaps in the blades you should be good.
With your calipers fully closed hold the blades toward a light and look for uneven gap. If you see more light at bottom and none at the top, then they are out of calibration.