1 inch = 25.4 mm's. I keep my little Casio pocket calculator handy at all times. I can convert easier than reading those metric tools unless it is a digital, which I have not acquired one of. I still use my "Old Fashioned" tools to measure Old Fashioned guns.
It is utterly amazing the fits old timers gut using nothing nothing but a pair of spring joint calipers, one inside & one outside. When I was an apprentice one old timer told me about working in a railroad shop in his younger days. He described how he had to fit a large diameter wheel for a Shrink fit to an existing band using spring joint calipers. The inside one was set to the ID of the band & the outside one set to the inside one. The wheel was turned down until the caliper could be "Sprung" across the top. When he got Ľ" Drag, IE the distance from where the caliper got tight on one side to here it loosened after dragging over the top on the other side the amount of Shrink was perfect. The band would then be heated & placed on the wheel & when cool it was shrunk to Stay, Permanently.
Never sell old timers short.
I can tell the difference between a 1 1/8" & a 1 3/16" firing pin spacing using nothing more than a cloth tape measure from Joann's, I can certainly do it using a precision set of calipers, & that's just stating facts, not bragging, just to keep the record straight.
