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

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....)

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