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

[Superhawk996]

You're probably not going to like the answer.

I'd just start with a fresh shaft.

Options I'm aware of:

1) Carbide drill and carbide taps. Neither are cheap and both are painfully slow cutting. Carbide is also brittle by nature. Carbide is prone to chipping and breakage with tool vibration & chatter. If you break off a carbide you're screwed and only recourse will be to EDM it.

Here's a solid carbide M6x1.0 tap -- $163 each! (IMG:style_emoticons/default/yikes.gif)
https://www.mscdirect.com/browse/tnpla/3144...ASABEgK12fD_BwE

2) EDM the threads in. Yes it can be done. You won't like the costs involved to do it.


https://www.youtube.com/watch?v=x3hEXA_q-dE


Maybe someone else has good ideas but my past history of drilling tapping hardened shafts as DIY has a spotty track record and that is with a vertical mill and a lathe at my disposal.

[brant]

You're probably not going to like the answer.

I'd just start with a fresh shaft.

Options I'm aware of:

1) Carbide drill and carbide taps. Neither are cheap and both are painfully slow cutting. Carbide is also brittle by nature. If you break off a carbide you're screwed and only recourse will be to EDM it.

2) EDM the threads in. Yes it can be done. You won't like the costs involved to do it.

Maybe someone else has good ideas but my past history of drilling tapping hardened shafts as DYI has a spotty track record and that is with a vertical mill and a lathe at my disposal.

I have the fear that you are correct. and I need to build a different transmission... alot more work. I guess the good news is that I have a lot of decent core parts now