Lead screw or thread dial not right?

twhite said:
You need to cut a full thread. Do not run it in reverse with the threads engaged. Back out then reverse. Go far enough back out to allow any backlash to be removed. If it will cut the threads correctly over all those passes. You may have fixed the issue with the half nut gib adjust. If notI think might you have something loose like your gibs or other components. Go through and make sure everything is tight and gibs adjusted correctly cross slide and compound.


Cutting oil is my blood.
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I can cut fine if I engage at the same number every time.
 
Although one can thread certain threads using various numbers on the dial, I have made it a habit to choose #1. This slows you down, and forces you to carefully choose the engagement point. Since I'm not in a hurry, or production environment, it helps me get it right every time. This may not work for you, but it has helped me. Worth a try anyways.
 
I move the carriage away from the chuck until I am near my preferred number. It does not seem as long as waiting for the number to arrive.
 
Parlo said:
I move the carriage away from the chuck until I am near my preferred number. It does not seem as long as waiting for the number to arrive.
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I've been known to do that too. But practicing patience is not a bad thing to do either. Builds discipline.
 
twhite said:
You need to cut a full thread. Do not run it in reverse with the threads engaged. Back out then reverse. Go far enough back out to allow any backlash to be removed. If it will cut the threads correctly over all those passes. You may have fixed the issue with the half nut gib adjust. If notI think might you have something loose like your gibs or other components. Go through and make sure everything is tight and gibs adjusted correctly cross slide and compound.


Cutting oil is my blood.
Click to expand...
Do this, but Ill add to slightly tighten the saddle lock screw to add some drag to take out additional slack.

Not much mind you, just enough you can feel it manually moving the saddle.
 
RaisedByWolves said:
Do this, but Ill add to slightly tighten the saddle lock screw to add some drag to take out additional slack.

Not much mind you, just enough you can feel it manually moving the saddle.
Click to expand...
This is especially important when threading away from the chuck as there is no time to take up any backlash.
 
Parlo said:
This is especially important when threading away from the chuck as there is no time to take up any backlash.
Click to expand...

If your threading away and engaging the half-nut with a running gear train, the backlash is removed as soon as it's engaged. If you thread in and then thread out without releasing the half-nut, then there is backlash. If you have the half-nut engaged and thread away, you normally go toward the chuck and back to thread start by turning the spindle by hand or jog to remove the backlash.
 
I know you guys are talking backlash, but the machine is brand new, with replacement parts. so no wear on the half-nut. the gears should all be meshing correctly, so backlash from traditional sources should be minimal. When I do the forward/reverse test on my 41 year old 12"Taiwanese lathe or my 40 year old 15" LeBlond lathe, you cannot tell the difference in the forward or reverse scratch impressions.

The forward/reverse test is only to test the half-nut engagement, nothing else.
 
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