Threading on Sherline lathe

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22 Apr 2017 15:08 #91845 by andypugh
G76 should work. But your spindle speed will be a problem.
If you can't get more Z speed the other option is to turn the spindle by hand. LinuxCNC can still sync to a hand-cranked spindle.

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22 Apr 2017 15:47 #91849 by Boltonbrass
I used a gear reduction attachment from Sherline and I made perfect threads this morning.
Thank you for the help. Next will be to get the 5i25 mess kit to work.

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03 Aug 2017 18:37 #96982 by techrat
Replied by techrat on topic Threading on Sherline lathe
Just jumping on this thread (Pun intended) quickly as I have been battling with getting G76 to work predictably on my lathe. I am wondering if you had more difficulty with G76 or G33? Did you start using G33 and saw better results? My current challenge may be related to the Q factor on G76 as it appears as though my tool is advancing too far with each subsequent pass and I end up with a wide flat at the root of the tread and a sharp point on the top of the thread.

I will probably work with G33 to simplify and see if this helps but am also interested in your experiences with switching between the 2 G Codes.

Thanks,
Jeff

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07 Aug 2017 10:41 #97099 by andypugh
Why not try a smaller value for Q if you think that is the problem? On manual lathes I have typically used a value of 0 and it works fine. (ie, apply cut with the cross-slide not the compound)

What type of thread are you cutting? Commonly used thread angles vary between 47.5 (BA) and 80 degrees (Panzergewinde) and you would typically set Q to fractionally less than half the thread angle.

I have never checked, but it is possible that the angle changes depending on whether one is in radius mode or diameter mode (it shouldn't, but....)

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07 Aug 2017 11:36 #97101 by techrat
Replied by techrat on topic Threading on Sherline lathe
Thanks for the reply! Over the weekend I decided to go through everything from the ground up and double checked my set-up. In the end, it boiled down to some really basic errors in the physical set-up of my machine rather than the program or control. After re-grinding the tool myself and setting it properly, my test thread came out perfectly first try.

Just a good reminder for me to start at the beginning when troubleshooting.

Thanks Again,
Jeff

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