Calipers, particularly cheap one, are to be considered a roughing tool.Harold_V wrote: ↑Sun Aug 25, 2019 1:34 am Don't make the mistake many make, using a caliper, be it dial, vernier or digital, for critical measurements (that's what micrometers are for). Such instruments are not capable, not even in skilled hands, of making readings when you are working closely (tight tolerance work, like fitting a bearing). You won't be exempt---no one is.
If you need to have a part within a few thou, they can be good enough. If you need something to within a thou, you need a mic.
Your 1" mic will be your most important tool - get a good one. I picked up a Starrett mic with carbide faces that reads to 1/10,000" (commonly referred to as 10ths) at an estate sale for $10. It's still my go-to mic 10 years later. Get one with a vernier scale (it's what you read the 10ths on) and learn how to read it. You can find youtube videos on reading vernier mics.
Do I have calipers? Yes, several. My favorites are my Starrett mechanical dial and my Mitutoyo digital, but I also have Starrett vernier calipers in 6", 12" and 24" and I can read them almost as fast as the dial and they NEVER go out of adjustment.
Use your calipers to check the progress on taking a 1" bar down to 1/2". When you get within maybe 30 thou, verify the diameter with the mic, take a pass at 10 thou, check with the mic (see if you are over or under), take off half of what's left, check with the mic, and take off the remainder.
Oh, and on the jobs where you need to work to a couple of thou? Do them to the thou for practice. Got a job where you need it to a thou? Do it plus or minus a few tenths.
If you can't work to tenths when you don't need to, you can't when it counts.
Steve
