In article ,
Harold & Susan Vordos wrote:

"SteveF" wrote in message
.com...
Let's say I have a small lathe (length) and need to make a threaded screw
longer than the max length of my lathe. Obviously this can be done in
theory by just threading one part, removing from the chuck, reinserting
further back in the headstock and continuing the thread. But in practice
can this be done with enough accuracy for something like a replacement
lead
screw for a lathe? Yes, I am aware of parts on Ebay and long threaded
rods
from MSC, etc. - this is more of a "how to use my lathe" machining
question.

[ ... ]

Given the proper setup, it's possible, but would be a serious challenge,
especially if you are new at machining. You'd need a follow rest, possibly
a steady rest, be able to feed the material through the headstock, and be
able to pick up threads properly. Having considerable skill and experience
would be the most valuable asset, along with soft jaws. Depending on how
you pursued the project, you might be limited to length, but you could cut
one longer than the center length of the machine.

If I had a choice for this, I would probably use a Geometric Die
Head to do it. Make the first cut as far as the turret would feed, then
(after the head released), reposition the stock through the spindle, and
close the Geometric on the existing thread, perhaps an inch or two from
the end of the cut thread. Then switch spindle on again, and feed until
end of turret travel again.

If I were dealing with an Acme thread, or even a particularly
coarse thread, I would use a Geometric Die Head with the rough/finish
switch lever, and do two passes for each section.

Actually, I've never seen Geometric chasers for Acme threads,
but I could imagine them existing.

Enjoy,
DoN.
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