Tap size for right side of rear sight housing?

[KYGun]

The parts I have has a nut for the sight screw. But old back piece has a threaded right side hole. What threads on a tap do I need to buy? Or can I drill it through as the left side is and the nut secure it?

 

[scottz63]

It is 1/8" BSW (British Standard Whitworth) but good luck finding that tap easily. 5-40 UNC is close enough to work fine though.

Edit: That little nut is intended to lock the screw in place so it does not back out, not to secure it all on it's own.

 

[heimue]

https://www.amazon.com/British-Standard-Whitworth-Pieces-Toolzone/dp/B006B3NE3U

 

[KYGun]

Got a 5-40 UNC coming....I'm assuming the tap will go in from left side through drilled screw hole to tap right side? One can't really tap it from the right side in as that'd reverse the threads, lol.

 

[scottz63]

Got a 5-40 UNC coming....I'm assuming the tap will go in from left side through drilled screw hole to tap right side? One can't really tap it from the right side in as that'd reverse the threads, lol.

Nope, you can tap it from either side, it won't "reverse" the threads. Think of a nut, you can put a bolt in a nut from either side. The only way you can "reverse" the threads is with a left hand threaded tap.

 

[KYGun]

good point. I hadn't done it so couldn't picture it in my mind.....