Not a new idea but I thought I would post my latest use of a tool I did not have.
The price of broaching sets is right up there to the point of tools I would like but
have not purchased yet. Since my new pulley needed a keyway slot and it was
made from aluminum I thought I would try the lathe method.
On hand were a couple of cutoff tool bits that I don't use on my lathe since they
are a bit on the large size for a mini lathe. So I mounted one HORIZONTALLY in a
tool holder and went to work. The pully was still attached to the 3.5" chunk of
aluminum round stock. I only took .001" on each pass to keep the pressure down.
After 30 minutes I had "broached" a 4mm keyway in my new pulley. Since I was
broaching in a blind hole I added an extra step to move the cut curl inside the
pulley after each cut. This doubles the time to complete but was necessary
to get the "chip curls" out.
One thing to note is the steady rest. It is being as a spindle lock in this picture to
hold the pulley firm and not allow it to rotate. Don't forget to unlock it prior to
running the lathe with power! No I did not do that, just thought I would mention it for safety reasons.
This should work with steel but I would take a .0005" cut for the first attempt.