My father needed to cut 34 tpi threads so his custom CCD camera
adaptors could be mated to his telescope. Neither his South Bend
9" nor my ATW cuts 34 threads, so we worked out a replacement gear to
be mounted on the quick change box of his lathe which would "speed up"
the 32 tpi setting and in fact cut 34 tpi.
We decided a 54 tooth gear would do it, and since it was for a few jobs
in aluminum, we also decided to do the gear in aluminum since its easy
to work and he already had stock at hand.
I prepared a blank. As expected, parting this was a big problem
but I eventually got it done.
I also prepared a mandrel out of scrap. The knurled piece is also
a bit of scrap, complete with hole off center.
I bought a #3 18dp cutter from Victor and set it up on the
Nichols. The long overhang isn't the best idea but with the 1-2-3
block & adjustable angle underneath it worked out OK. If the
gear were steel it probably wouldn't have worked out.
Back to the lathe to face off the burr left on the trailing face, and
slightly chamfering the teeth.
I broached the keyway using the Bridgeport slotting head and the gear
Installed on my father's lathe, it was a little noisy for a while but
quieted down. He succeeded in making several 34 tpi threads