"SJ" wrote:

It would be relatively easy to single point a 4-start thread on a CNC lathe
with a C-axis, but not having access to one, how would you cut a 4-start
1/4"-20 thread on a manual small lathe (like the mini-lathe)?

Thanks,
Sam


I cut 4 start 36-TPI all the time on an Atlas 618. While I use the
proper depth of cut for 36 TPI, the lathe gearing is set to 9 TPI. My
thread dial has four marks and each mark works a different start (this
may vary on other lathes). I make a pass for all four starts, then
advance the compound for the next one.

Once I needed to do a 4 start 32 TPI and I just couldn't work the
thread dial the same way. I had to cut two threads to depth, and then
I slipped the gearing from the tumbler to the spindle 1/4 revolution
and did the other two threads.

For internal threads, extra clearance was required on the tool.

-Bruno