No. 4 Help

[Calif-Steve]

I have tried 2 screws. The threads are gone on the rear screw hole. The receiver needs a real cleaning and likely a Parkerizing job. I might blue on top of the Parkerizing as well. The tap and dies sets are on Ebay from the UK, so I think I will try that route. Thank you very much for the help.

[Peter Laidler]

If you need UK spec phosphating and sunkorite painting, try Brian at BDL.

[browningautorifle]

I might blue on top of the Parkerizing as well.

That's not possible. Blue is a solid salt that dissolves in water and is applied at a temperature, it causes a reaction deep inside the pores of the metal. Parkerizing is a liquid that dissolves in water and is applied at a temperature...different to blue. It forms a crystalline structure on the surface of the metal. It's far more durable than blue thus being adapted for military weapons. The surface for blue must be polished and fine, or you get a matt finish. The surface for parkerizing should just be bead blasted or sand blasted and gives you a corresponding finish. If you try to put one over the other, you'll end up with a surface that resembles a calico cat's coat, except not fuzzy and pet-able.

As suggested, just ship it to BDL and he'll make good and return...

[Patrick Chadwick]

Can I assume that it is the thread in the BODY that's stripped? If so, then in our life, that's the end of the line I'm afraid. But it'd be a poor craftsman who couldn't fix it. If it were me I would drill out the stripped thread and silver solder in place a steel insert. Then set the body up on a drilling/milling table and re-drill and tap to the usual 94BA or whatever it is. I suppose you could get a good tig welder to fill the hole in and drill and tap.........

Well I have BA equipment down to 16BA, and some sub-mm wtachmakers tooling, but 94 BA could be tricky. So as poor weather stopped gardening, I attempted to work out what 94 BA would be. You need to know that pitch of 0BA is 1 mm and the pitch of each higher numbered thread is obtained by multiplying the pitch of the lower number by 0.9 so K-BA has a pitch of ${\displaystyle p=0.9^{K}}$ rounded to two significant figures in mm. The major diameter is given by ${\displaystyle 6p^{1.2}}$ rounded to two significant figures in mm and the hex head size (across the flats) is 1.75 times the major diameter.

94 BA works out to a pitch of about 50 nanometers.

No wonder I can't see any in the spares box!

[Peter Laidler]

I only mentioned that deliberate mistake just to see if everyone was awake and not falling asleep at the back of the class! Well done Patrick!