Cutting wooden threads

L

littlewing1208

Registered
Hi,

I watched a youtube video of someone cutting threads (looked like 3/8x10) in a shaft on a lathe. He did it in 2 passes. My question is how does the machinist and/or the lathe know when to start the 2nd pass so that it follows the same helix/spiral of the 1st pass?
 
A machine lathe capable of threading has a thread dial. Any time the carriage is moved it turns. Any time the spindle turns and the lead screw is turning the dial turns. When both move tovether the dial turns taking both into account. The dial has numbers on it. Engage the half nut to the lead screw and make cut 1. Disengage and reposition. Engage again on correct number. Everthing is in time if stock and cutter/compound are not moved.

The correct number on the thread dial may vary from one lathe To another but generally even number of threads you can engage on any number as long as you stick to even/odd on subsequent cuts. Odd number of threads you must engage on odd numbers on thread dial each time.

YouTube should help you understand if you search for thread dial.
 
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By looking at the number in the dial when he started his first pass.
On the second pass, he starts threading on the same number .
 
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A tip for owners/users of thread cutting metal lathes.
If you are not cutting threads, don't have the thread-dial engaged.
To do so is to wear-out parts needlessly.
Loosen the bolt/nut and swing it out of the way until needed.
Also, if you're not using the pwr-fd at the moment, disengage the leadscrew.
Reread sentence #3. Turn out the lights when you're done.

KJ
 
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