Ever Checked?

[joatmon]

The real size of those pin gauges? I was checking my .38 and .357 cyl throats and thought I'd check them with a mic, These are +.002 I think! Here's the mic readings.
.356 reads .3556
.357 " .3569
.358 " .3575
.359 " .3586
.360 " .3596
My Smiths were the tightest @ 3556 and my 2 uberti's @ .360 the largest.

Just wondering Aaron

[Reverend Recoil]

Those appear to be 0.0005" minus pin gauges. They are the best type for gauging holes. You cannot easily insert a 0.3580" pin onto a 0.3580" hole. If it is forced it will likely seize and may never be removed.

[Buckshot]

Those appear to be 0.0005" minus pin gauges. They are the best type for gauging holes. You cannot easily insert a 0.3580" pin onto a 0.3580" hole. If it is forced it will likely seize and may never be removed.

............Very true about using minus sets. All my pin gauge sets (from .061" to .750") are .0002" Minus sets. While not as sensitive to temperature as a very good set of gauge blocks, which even import economy set's run to 0.00005 accuracy, the pin gauge you're using and the hole it's going into needs to be REALLY clean for an accurate reading.

And not to get too far into the weeds, how confident are you in your 'Tenths reading' mic"? I did machine work for about 12 years and had a Mitutoyo 0-1" tenths mic that was used regularly on the bench. Early on I had also bought a new Starrett which was only seldom used as a backup and was kept in my rollaway. Ditto a new Swiss made Brown & Sharp I escaped with on E-Bay when everyone else must have been asleep :-)

The 'Using' Mitutoyo was checked twice a year (4th of July and New Years) in 4 places with 1/100,000" gauge blocks. Mic's can wear, and usually in the lower half of their range. Also HOW they're used (even the ratchet handle types can lie) will have a definitive result in the accuracy they deliver.

.............Buckshot