When I use dial calipers, I maintain the same thumb pressure, clean the jaws, and zero often. I try to rock them into perpendicularity, and measure with the same spot on the jaws each time. I check my accuracy with pin gauges. I interpolate between the .001" hatch marks with my eyes. My eyes can easily resolve .0002", but .0001" is harder.0) My 8 year old Midway $20 Chinese 6" calipers can be trusted to .0002" 1) My new Enco $14 Chinese 6" calipers can be trusted to .001" 2) My new SPI $25 Chinese 6" calipers can be trusted to .0025" 3) My new Mitutoyo $72 Brazilian 6" calipers can be trusted to .0002"
The thing of interest was the $25 SPI looks like it is the same as the $14, with nearly the same serial number sequence on the back. But the SPI costs more and are not as good. The "SPI" name has been w**re'd out to Chinese junk.