Re: screw pitch gage
The only way I can think of a screw pitch gage changing would be wear from a lot of screw sorting, unless someone decides to use it as a "comb" to brush away grime on the threads... :mg:
Anyway, I came across a procedure from Starrett (for their cat. no. 6, 155, 472, 473, 474 and 484 gage sets). The accuracy is ±.002" between any two teeth, and 60 ± 1 degrees for 20 pitch and coarser, and ± 2 degrees for finer than 20 pitch. Their procedure is as follows:
1. Appearance- visially inspect the gage for finish and proper markings.
2. Inspect for correct number of leaves.
3. Inspect for operation of the locks.
4. Inspect for accuracy.
It's #4 that I was curious how other people did it. I think the quickest and easiest way is to compare it against a known good gage (read: one that hasn't been abused) with the optical comparator, maybe stack them, mesh the teeth together, or make tracing paper overlays with a pencil and straight edge?