"Mechanical Magic" wrote in message
...


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

Harold,
No, I was very serious.

But, to clarify, the error I tend to make with that thimble is being
off by .025" or .050" because I misinterpret the direction. So, I'm
using the caliper to that accuracy.

I don't know why I have such a problem with those inside mics, never
have a problem with depth mics or normal mics.
Maybe it's a dsylxic tool?

I could not agree with you more, about the accuracy of calipers (on an
outside measurement), and the need for developing a "feel" when using
measuring tools. I learned the art of telescope gage use 40 years ago
while boring motorcycle cylinders. That said, I am more comfortable
using an inside mike and a direct measurement, which still requires
the same level of "feel", practice, and calibration of the measuring
tool.

Where I disagree: measuring a smallish hole with calipers. To suggest
that +-.005" is to be expected, is leading the inexperienced down the
wrong path. I have tried all my calipers with a .2000" ring, and they
ALL read a smaller diameter, by different amounts. I don't believe a
hole measurement to within .010"

Dave

Are you talking about spring calipers or sliding calipers, Dave? If we were
to sit down and try it together I could demonstrate repeatable accuracy in a
2" ring of +/- 0.002" with spring calipers; probably half that with good
instruments. An expert can do even better. But if you're talking about
sliding-scale calipers, they're next to useless for measuring the inside of
a ring.

--
Ed Huntress