Brent Philion wrote in
:

As much as it sounds like a nice peice of machining what is a 4 start
thread used for?

Fast lead. In the example here a four start twenty pitch thread will move
the nut 0.200" per revolution versus 0.050" per rev for a standard 20
pitch.

So, why not just cut a five pitch thread and be done with it? Well in this
case the major is 0.250", a five pitch thread would be so deep that there
would be next to nothing left at the minor diameter. The 20 pitch four
start is shallower and leaves a lot more material at the minor diameter. So
the multi start thread gives you a fast lead and more strength.


On Sat, 01 Apr 2006 23:02:43 GMT, "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)?


BTW,

You don't need a C-axis to cut a multi start thread on a CNC. You simply
need one pulse signal from the spindle. You don't even really need an
encoder on the spindle.


--

Dan

Quid Aere Perennius