Most razors have tang holes that are 5/64 in size some are punched holes or worn holes that will fit a 1/8 size pin/screw but many of those are not round... Be prepared to do some modification of tang holes as soon as you go above 1/16 pins/screws
Good point. The hole on my Genco wasn't even close to round. It was small too. A straight-flute carbide bit is your friend in these situations.