Harold and Susan Vordos wrote:

"Jordan" wrote in message
. au...


I made a bolt for the kickstarter of a friend's motorbike, as the
standard ones always bend. Used 4140 high-tensile steel, but now
thinking it might be improved by heat treatment.
But I've virtually no experience with this process, so:

Does it make sense, given that there is a thread on the bolt?
Will scaling or warping change its size and shape?
Is it easy enough to do?

Thanks
Jordan



Yes, it's fairly easy to do, but without a controlled atmosphere furnace, or
stainless foil, your chance of not screwing it up is not good. For one,
when you heat and soak the part as prescribed, you'll experience some
decarburization, and scaling will pretty much ruin the surface. Warping
can be controlled somewhat by proper quenching, but even that can be filled
with surprises. Chrome moly can be heat treated by torch, but you'll
still experience considerable scaling. If you'd like to try, heat to
1525/1625 F, and quench only in oil. I don't have a clue regards drawing
it after quench. I've always had heat treat done by a certified heat treat
facility, of necessity.

A good choice for the job you did is to use some pre-heat treated 4140. As
I recall, it comes hardened to somewhere between 28 and 32 Rc-----tough, but
quite machineable.

Harold


A useful trick is to rub soap (plain bar soap) over the metal surface.
It won't prevent discoloration and a small amount of oxidation, but it
will prevent any significant scaling. Depends on the item, try on a
spare piece first...

Steve