I need to screw down a rear sight base. The base appears sized for a #6 screw, possibly a #8. I have .28" of barrel wall thickness to work with. The local hardware store has 6-32 & 6-40 taps, but only 6-32 screws.

What is the best hole depth/screw size/thread pitch combination?

Get a 6-48 tap from Brownells and a #31 drill. This is standard sight screw thread. Don't use any other size as it will screw up the next person that needs a screw for the hole. Leave at least .125 wall from bottom of hole to bore.

If you don't have a good drill press or milling machine take the gun to a smith to get the job done right. I can't tell you how many guns I have seen that have been ruined by home "gunsmithing".

quote:

Originally posted by srose:
Get a 6-48 tap from Brownells and a #31 drill. This is standard sight screw thread. Don't use any other size as it will screw up the next person that needs a screw for the hole. Leave at least .125 wall from bottom of hole to bore.

Just the kind of advice I was looking for, thanks.