"JWho" wrote in
news:2Ehbf.547233$xm3.377596@attbi_s21:

I think I am going to look on eBay for a used name brand micrometer.
Is there some way to check to see if it is accurate? Do they come
with a metal bar that is .5" or 1" exactly or something like that?? I
thought I saw something in a set at Harbor Freight. Is a micrometer
adjustable to get it back to accurate? I'd hate to buy one off eBay
and it be inaccurate. Also, there are so many different models that
it is confusing. If I get one off eBay, it won't be a Chinese one. I
can just go get a new one from Harbor Freight instead of eBay.

All micrometers are adjustable as far as I know. All of the brand name
ones are for certain. Most come with a "standard" which is a 1" long rod
(for a 0-1" and a 1-2") that you can use to set zero. Often there is no
standard with 0-1" micrometers, because you can just close the anvils and
make sure it reads zero.

To truly check out a micrometer requires tools that few machinists own.
You would need a set of gage blocks and an optical parallel along with a
light source. Plus an indicator. You would check the readings against the
gage blocks at 90 degree intervals throughout the travel of the
micrometer. You would then use the indicator to check the run out of the
spindle at various points in the travel. Then you would use the optical
parallel to check the flatness of the anvils and thier parallelism.

Trust me. If you buy a newer brand name micrometer off of Ebay you really
won't need to do this. I've checked some vintage tools I collect just for
the fun of it, and surprisingly 50-100 year old well used micrometers
rarely have a problem.

Individual gage blocks and micrometer standards are listed frequently on
Ebay. If the micrometer of your dreams doesn't come with a standard, you
can pick up an individual gage block or micrometer standard cheap and
easy. Once you get a mike, just let us know what it is and you'll get
help here on adjusting it.

I also read where you work in metric. You'll find good quality metric
micrometers are a little more scarce on Ebay than inch ones. But they
usually sell for cheap and are as a rule in very good shape.


--

Dan