what is the technique for a stripped thread in hardened material?, how to re-tap a pinion shaft threads / Tranny problems Options

[brant]

Ok...
so I had a big transmission failure
this box was built by a friend, at a clinic

I'm guessing the 30mm Bolt (for the speedo drive) was not torqued correctly?
apparently it came loose

the stack slid
and drove the brass angle drive through the back of the tail cone

the little button in the picture is the plug from the magnesium tail cone

but as you can see the bolt threads were heavily damaged
I have a replacement bolt with good threads

but the threads inside the pinion shaft received some damage also
I have the correct tap
but the material of the pinion shaft is so hard, that I can't get the tap to start


What is the technique to thread something hardened?

I'm betting the process involved heat, and softening the metal then rehardening...
which may not be a good idea with a pinion shaft
so I may need to build a different transmission
but if I could tap this thread, I'd be willing to give this box a shot.


any metal experts out there.. or machinist know if this is possible?

thanks in advance
brant