"Mechanical Magic" wrote in message
...
There is another method for precision measuring of holes. Inside
micrometers.

http://www.shars.com/product_categor...de_Micrometers

I have been using them for years, and wouldn't be without them,
although I only have up to two inch.
Since the barrel travel is not intuitive (to me), I always check the
reading with a caliper to verify, or a calibrated outside micrometer
for precise measurements. The 2" does have some spring, and a good
feel is required to get better than .0005".

Chuckle!

You're joking about using calipers to verify your readings, aren't you?

I don't give a damn about the type of caliper, or how many places it will
display a reading, they can NOT be relied upon for measurements closer than
+/- .003", particularly if you're attempting a press fit with a pin, using
both inside and outside jaws. They're simply not made that precisely, nor
do they retain their original precision after being used for a period of
time.

Where I was trained, QC could not accept or reject any dimension closer than
+/- ,005" with calipers. They were caught way too many times missing the
boat by a thou or two.

Aside from dial bore gauges, or inside mics, there's nothing quite as good
as telescoping gauges in the hands of someone that knows how to use them.

Harold