Jordan wrote:

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



If you got an oxy/acytlene torch, a magnet, and a bucket of oil you can
easily heat treat it.

Set the torch with a reducing flame, one which there is an excess of
carbon. This will keep the metal from oxydizing. Heat the metal until
the magnet will not attract the steel. This is the point where the
steel changes...I forget what to what, but at that point you want to
quench the piece immediately. By the way, make sure you quenching oil
is about 140 degrees or the piece will chill too fast and crack. Also,
when you immerse the piece in the oil, do not pull it back out because
the smoke will flash and burn. Keep moving it while holding it under
the oil until it is cool. It will be in the full hardened condition,
for 4140 that will be about 56rc rockwell. Now you got to draw,
temper, anneal it, choose a word. What you do is to heat it back up to
about 600 degrees and then let it cool. 600 degrees is when the metal
turns a very light straw color. Sand off a place so you can see the
color change easily. I would practice on a piece first before you do a
finished piece.


John