Spot annealing

L

Licensed to kill

CGN Regular
Rating - 100%
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Location
Peace Country Alberta
Had the right idea to drill and tap the rear of the receiver in a Miroku 1885 only to find out the thing is hardened like flint. Drill bits and end mills barely touch it. So, I gotta try to anneal just that spot if I can. Tried a hot rod, nope. Thinking of trying to finally some heat block paste that I can encircle the spot to mitigate heat migration. I think I can drill the hole both a carbide bit but to tap it??? Perhaps I can drill the hole, then put a copper rod in the hole and heat the rod glowing red and to anneal enough to allow it to be taped? I dunno. Of course it’s a small tap as well (8-32). I do have another idea if annealing is not an option but annealing and taping is first choice. Thoughts?
 
I tried to install a side scope mount on my Dad's Model of 1917 some years ago - same issue - hard as can be. So, I used like 1/4" nut - oxyfuel flame into that nut - maybe did not go long enough - ended up to use a carbide bit on my drill press - who knew that the inside face was going to be as hard as the outside face!!! Centre was not bad to drill through. As I recall - I used three 6-48 screws - is room for two more, but that side mount did not fall off. When I had the hole drilled part way through, I re-did with the flame - that might have got the metal soft enough for that carbon steel tap. As I understand, a home guy can "smash" as CS tap, but can not "smash" a tool steel tap.
 
That one can break up with small punch - like when you get a tap broke off going into a hole - remnants of CS tap can be struck and will shatter - tool steel taps usually won't shatter - of course, most cheapest ones are tool steel, not CS.
 
I've drilled for a lot of 6-48 screws, these require a #31 drill bit. For hard receivers I've used a #28 carbide bit break the skin then switched to the #31 to complete the drilling. This leaves a neat entrance to the hole and any raised edges are on the #31 hole, which is under the exterior surface.
 
On super hard steel I used to use a small tip on my oxy/acetylene and adjust it to a fine point and try to heat the spot to a blue colour and then try and drill it... and repeat. And then drill for tap size and use new taps... a starting tap (if it isn't a blind hole) and when it gets tight use a plug tap until it gets tight and then back to the starter tap, repeat... all of this tapping done in the drill press by hand.
 
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