Would like to make threading dial for my 13" LaBlond lathe (circa 1947 ±)..
Lead screw (worm) is 1" in diameter and 6 threads to the inch. I assume it is either square thread or Acme.

Please help me select a worm gear to fit. My intent is to print the gear (once I find a CAD drawing) with my Prusa 3D printer. After all, it is simply a pointer with not much power being transmitted, ergo, ABS gear should last a while.

I might also try and design the entire mount out of ABS and print it. Although it would not be difficult to do a couple of cross drills on a block of aluminum. One hole for the shaft with the gear, and an other for the mount to the saddle.

All help appreciated.

Ivan Vegvary

On Sunday, December 21, 2014 6:50:16 PM UTC-5, Ivan Vegvary wrote:
Would like to make threading dial for my 13" LaBlond lathe (circa 1947 ±).
Lead screw (worm) is 1" in diameter and 6 threads to the inch. I assume it is either square thread or Acme.



All help appreciated.

Ivan Vegvary

Probably no help, but 6 threads to the inch sounds wrong. Are you sure it is 6 tpi. I would expect it to be 8 tpi.

Dan

"Ivan Vegvary" wrote in message
...
Would like to make threading dial for my 13" LaBlond lathe (circa 1947 ±).
Lead screw (worm) is 1" in diameter and 6 threads to the inch. I assume it
is either square thread or Acme.

Please help me select a worm gear to fit. My intent is to print the gear
(once I find a CAD drawing) with my Prusa 3D printer. After all, it is
simply a pointer with not much power being transmitted, ergo, ABS gear
should last a while.

I might also try and design the entire mount out of ABS and print it.
Although it would not be difficult to do a couple of cross drills on a block
of aluminum. One hole for the shaft with the gear, and an other for the
mount to the saddle.

All help appreciated.

Ivan Vegvary

Think of your lead screw as a rack. If it is 6tpi then it would have a
diametric pitch of 6tpi*3.14259.
18.84945.
In reality, anything from 18-20 dp will work for this application.
You will want a gear with a tooth count in multiples of 1" of screw tpi,
i.e. 6,12,24.
Pressure angle won't make much difference.
It doesn"t need to be a worm gear, a straight gear will work fine. But if
you want to minimize wear, you should design the mounting to cant the gear
to match the angle of the threads.

Paul K. Dickman

On Monday, December 22, 2014 7:26:17 AM UTC-8, Paul K. Dickman wrote:
"Ivan Vegvary" wrote in message
...
Would like to make threading dial for my 13" LaBlond lathe (circa 1947 Ä…).
Lead screw (worm) is 1" in diameter and 6 threads to the inch. I assume it
is either square thread or Acme.

Please help me select a worm gear to fit. My intent is to print the gear
(once I find a CAD drawing) with my Prusa 3D printer. After all, it is
simply a pointer with not much power being transmitted, ergo, ABS gear
should last a while.

I might also try and design the entire mount out of ABS and print it.
Although it would not be difficult to do a couple of cross drills on a block
of aluminum. One hole for the shaft with the gear, and an other for the
mount to the saddle.

All help appreciated.

Ivan Vegvary

Think of your lead screw as a rack. If it is 6tpi then it would have a
diametric pitch of 6tpi*3.14259.
18.84945.
In reality, anything from 18-20 dp will work for this application.
You will want a gear with a tooth count in multiples of 1" of screw tpi,
i.e. 6,12,24.
Pressure angle won't make much difference.
It doesn"t need to be a worm gear, a straight gear will work fine. But if
you want to minimize wear, you should design the mounting to cant the gear
to match the angle of the threads.

Paul K. Dickman

Paul, thank you so much for your detailed answer!!
Your answer is thorough and will help tremendously.
Ivan Vegvary

"Ivan Vegvary" wrote in message
...
Would like to make threading dial for my 13" LaBlond lathe (circa 1947
±).
Lead screw (worm) is 1" in diameter and 6 threads to the inch. I
assume it is either square thread or Acme.

Please help me select a worm gear to fit. My intent is to print the
gear (once I find a CAD drawing) with my Prusa 3D printer. After all,
it is simply a pointer with not much power being transmitted, ergo,
ABS gear should last a while.

I might also try and design the entire mount out of ABS and print it.
Although it would not be difficult to do a couple of cross drills on a
block of aluminum. One hole for the shaft with the gear, and an other
for the mount to the saddle.

All help appreciated.

Ivan Vegvary
===================

Perhaps you could copy a short section of the lead screw in drill rod
and turn it into a hob for an aluminum gear. In my experience an
unhardened cutter without back relief can cut one or two aluminum
parts per sharpening of the radial cutting edges.
-jsw