Chassis rivet size?

[Bob Kneale]

I made up the most of the snaps we used although some of these broke due to faulty heat treatment! A reground twist drill made an excellent form tool to make the semi-spherical indent in the snap. I used silver steel as the base material.

Another way to make the hemispherical indent in the snap is to hammer a suitable sized ball bearing into the snap (we've all got lots of scrap ballraces around).
Heat treat the finished snap and it will serve you well!

Good luck.