"Larry Jaques" wrote in message
...
On Mon, 14 Feb 2005 12:29:48 -0800, the inscrutable "Harold and Susan
Vordos" spake:
snip--

.. A good press fit has a narrow window---no more than a couple
tenths-----and you can't do it (reliably) with the typical caliper. You'd
have better luck with a spring caliper and a micrometer.

For my use, a few thou won't make much difference and I'll buy or
borrow a mike if I need real precision.

That's really the key in this discussion. If your needs are not critical,
there's absolutely nothing wrong with calipers, be they vernier, dial or
digital. I'm still using the first ones I bought, back in '57, made my
Helios. They've been to hell and back, including being lost off the roof
of my truck years ago. I got a strange phone call one day from a guy asking
me if I owned some calipers with my last name on them. "Sure do", I
replied, "they're right out in my shop, in my toolbox."

"Nope", he replies, "I have them right here in my hands. The last letter of
your name, the s, is missing. It was then I realized he had my calipers.
When I electroetched my name on them the s didn't print.

He found them in an intersection about two miles from my home at that time
in Utah.

I was employed as a QA inspector for an electronics firm in the 70s
and used dial calipers and vernier height gauges.

QC used the same tools, but in addition used fine dial indicators and
Cadillac Pla-chek instruments for measurements. They left nothing to
chance.

I was taught by an
ex-missile industry QA geezer who told me how to get better precision
out of an inferior tool. (Most of our stuff was Starrett, but you know
what I mean. He was used to being around optical comparators and other
nice stuff.) I can read a few tenths difference between two parts
using a caliper with a thou face. And having precision blocks helped
me get a feel for proper caliper use. I don't "bend to fit" any more.

That's the toughest thing to overcome. When I was grinding, I got used to
never looking at the mic while I was checking diameters, trusted my feel
exclusively. When you do that, you learn to do it consistently----which is
the main reason I keep harping that one can read mic's to .000050",
especially if you have good surfaces.

P.S: My first day there he made me promise I wouldn't use any of the
Starrett (or other) tenths mikes for C-clamps. That got a good laugh
all around.

But how many do so? I had a strict policy where my measuring tools were
concerned, and I still enforce it, although there's on one to borrow them
now. I permit NO ONE to handle my measuring tools. Anyone asked when I
worked with others, I told them to buy their own, just as I did.

Harold