3/16" verses #10 machine screws

[Fordors]

The "old toolmaker" way to determine what diameter rod is used for machine screw sizes is to take the number size and times it by .013 and then add .060. Example for 10-32 is 10 X .013 = .130 + .060 = .190; .190 being close to 3/16 so the #10 screws are that size. The 12-24 screw would be 12 X .013 = .156 + .060 = .216; .216 is just under 7/32.

[Terry, NJ]

Cute Trick! I'll remember that one! You are correct, #10s are interchangeable with 3/16, and #12s are 7/32. Little story, I once found an old, large coffee can that was about half full of 1/4-20s 12-24 and 10-32 SS Oval heads among a lot of other stuff for $.50. I didn't realize that the 12-24s were in there till I got it home and started poking around in it. I've never found any since. You get a little lucky now and then.
Terry

Originally Posted by Fordors

The "old toolmaker" way to determine what diameter rod is used for machine screw sizes is to take the number size and times it by .013 and then add .060. Example for 10-32 is 10 X .013 = .130 + .060 = .190; .190 being close to 3/16 so the #10 screws are that size. The 12-24 screw would be 12 X .013 = .156 + .060 = .216; .216 is just under 7/32.