GO765 thread cutting, not indexing

[dkccfl]

Hi all, been trying to learn to cut threads on my GO765 and all attempts have look real bad so far. In an effort to try and sort it out I came up with the idea of running two scratch passes back to back and ended up with a double track. The manual says to use numbers 3 5 or 7 when cutting 20 TPI I tried 5 and then 7 on two different tests with the same result. Any ideas on what I should check? Thanks, Dale

 

[jaek]

Is your picture showing a wide blue stripe, one scratch pass, a very narrow blue stripe, and then another scratch pass?

1) Try using the same number on the threading dial for every pass. With an inch leadscrew, this should let you cut any whole-TPI thread pitch.

2) Try not disengaging the half nuts. Cut a thread pass, stop the lathe, back out the cross slide, run the lathe backwards past the end of your workpiece, run the cross slide back in, run the lathe forwards to cut another pass. This should let you cut any thread pitch on any lathe, for example metric threads on an inch lathe.

 

[RJSakowski]

Have you checked the thread pitch?

A problem that I had with my Grizzly G0602 was the thread dial was not marked concentric. I made a new dial and everything is good.

Threading On A Grizzly G0602

On March 19th, I replied to a thread begun by Cody Killgore entitled "Threading, Something Went Wrong Here" (post #19) where I show evidence of an problem with the threading dial on my Grizzly G0602. I had determined that the dial markings were not concentric with the gear shaft, creating an...

www.hobby-machinist.com

 

[RJSakowski]

Another issue that can arise is the dial isn't clocked correctly so the half nuts engage slightly before or after the mark. At a casual glance, it looks good but you won't track properly unless you hit the same side of the mark each rime. This can be corrected by loosening the screw and rotating the dial for correct registration.

 

[dkccfl]

Another issue that can arise is the dial isn't clocked correctly so the half nuts engage slightly before or after the mark. At a casual glance, it looks good but you won't track properly unless you hit the same side of the mark each rime. This can be corrected by loosening the screw and rotating the dial for correct registration.

Thanks, I think that may be the problem. It seemed to lag the mark a bit then engage. I did not know the dial could be rotated, Thought it was indexed with a key or spine. I will investigate and see what's up.

 

[dkccfl]

Is your picture showing a wide blue stripe, one scratch pass, a very narrow blue stripe, and then another scratch pass?

Yes, there is a tiny stripe between the two scratch passes.

1) Try using the same number on the threading dial for every pass. With an inch leadscrew, this should let you cut any whole-TPI thread pitch.

2) Try not disengaging the half nuts. Cut a thread pass, stop the lathe, back out the cross slide, run the lathe backwards past the end of your workpiece, run the cross slide back in, run the lathe forwards to cut another pass. This should let you cut any thread pitch on any lathe, for example metric threads on an inch lathe.

 

[Mitch Alsup]

I just use the same mark every time--saves me from all sorts of mistakes without wasting too much time in doing it.

 

[jaek]

On your lathe there are sixteen positions where you can close the half nuts, even though there are only 8 lines on the dial.

The pattern you have show looks like what I would expect from one pass on a "whole" position and one pass on the nearest "half" position. This could happen due to the misalignment RJSakowski is describing, or it could happen from closing the handles a little too early or late.

"seemed to lag the mark a bit and then engage" sounds like you just missed one position and then ended up catching the next.

 

[dkccfl]

On your lathe there are sixteen positions where you can close the half nuts, even though there are only 8 lines on the dial.

The pattern you have show looks like what I would expect from one pass on a "whole" position and one pass on the nearest "half" position. This could happen due to the misalignment RJSakowski is describing, or it could happen from closing the handles a little too early or late.

"seemed to lag the mark a bit and then engage" sounds like you just missed one position and then ended up catching the next.

Thanks for the reply, I played around with the lathe a bit today and found the dial does move to any position when the screw is loosened. Did manage to get three scratch passes down as one but I still need to try and adjust it better.

 

[T Bredehoft]

Just to make sure, verify that there is about 30 degrees between your compound and the face of the chuck, not 60 degrees. This is a recurring problem.