Re: which calipers are worth it?
I just did some testing to compare cheap dial calipers to expensive dial calipers to a micrometer.
I used two pin gauges; .7031 inches and .251- inches.
I calibrated the calipers at .7031" and then measured at .251- to find the measurement error.
There did not seem to be any tracking error in the three instruments over the .452" range.
There were repeatably errors.
The cheap [SPI $20] dial calipers, give a dozen measurements, would vary .0020".
The expensive [Mitutoyo $80] calipers, given a dozen measurements, would vary .0002".
The micrometer [ENCO $50], given a dozen measurements, would vary .0002". That instrument is hard to calibrate. It takes tool(s).