Bob,
If you noticed in my first line, I was on about digital verniers.
I use a mechanical clock vernier most of the time if I can't get a mic in, and even cheap ones will give a better reading than a digital one. They are usually good to guesstimating to 0.0005" (depending on the accuracy of the scale), but again, they must be used the correct way to obtain that reading. That is pressure from forefinger and thumb either side of the jaws, and as close to the measuring point as possible, with your other hand just supporting (not holding) the long arm, with the reading taken whilst in contact with the job, not locked up with the finger screw and read when withdrawn.
I did a very unenjoyable stint in a calibration dept of a metrology lab in a factory standards workshop, and came across almost every mechanical measuring instrument you could think of.
The first thing we did with all calipers, it didn't matter whether mechanical or digital, personal or factory owned, we ground the internal measuring tips off because they were deemed just too inaccurate to be used, even when brand new.
Everyone in the factory had to submit their personal precision instruments for calibration if they wanted to use them in the factory, as using a non up to date calibrated instrument left them liable to severe disciplinary action.
This was just part of my job when working in a cleanroom factory making computer hard disk drives. In the workshops where they developed new drives, mostly from solid billets using manual machinery, measurement was a critical part of the manufacturing process.
So I got to use not only very expensive digital calipers, but the cheaper ranges as well.
Not one of them gave me confidence enough to call them precision instruments, and were all marked up for 'not to be used for critical measurement'.
Maybe a bit too much info supplied, but it does show that digital verniers are not what most people expect of them.
I expect some of the very expensive ones have most probably come on a lot since I used to work with them, but the cheap and nasties should never be considered for critical measurement, you are just asking for trouble. I treat them as similar to a six inch rule. They are scattered about the shop, and picked up and used for when I want a near enough measurement. When they stop working, they are thrown away.
I bought a digital micrometer a while back, but haven't used it yet, I need to check it out using slips before I will consider putting it into action in the shop It reads to silly numbers of decimal points, but it is no use if it doesn't give the same reading each and every time.
Bogs