Absolutely! They also make very fine circular parallels- but although they're not bad, two races of the same type may not necessarily be the -exact- same width. The "important" tolerances regard the diameters.
The problem I've encountered with feeler gauges, they are punched from sheet stock, and typically have a raised edge. They work OK for setting engine tappets, as the central part away from the edge is used. I have old used feeler gauges as well, that were used back in the day, and are all dented up from being used to set the valve clearance. I think this happened when the engine was running.
+8/-4 microinch max for grade 3, less then 1 inch. At least what I found. Seems the set I have, I've seen numbers that range +/-30 microinch on the calibration sheet included, so this must be an economy set of blocks.
