TL-2 Left Hand Thread Routine

[dhelms]

I just tried to cut a 5/8-11 left hand thread on my TL-2 and something seems strange about the canned routine. When you use the LH thread setting, it rotates the spindle clockwise and feeds right to left, so I figured I had to put the tool on the far side of the workpiece. Problem is...at the end of the first pass when the tool starts to back out of the cut, it moves toward the operator (in my case crashing into the workpiece). Is there something I'm missing? Thanks. -- Dave

[Geof]

Originally Posted by dhelms I just tried to cut a 5/8-11 left hand thread on my TL-2 and something seems strange about the canned routine. When you use the LH thread setting, it rotates the spindle clockwise and feeds right to left,....

Spindle rotating clockwise as you look at it? In other words running in reverse.

I think you need the tool upside down.

What threading cycle are you using? I have used G92 for left hand threads on a TL. Spindle running forward and thread away from the chuck, i.e. left to right.

[dhelms]

Yes -- the spindle was running in reverse. I was going to turn the tool upside down, but didn't have time to make a new holder.

The conversational menu generates code using G76 -- I wasn't aware of G92. I was playing with the G76, but couldn't get it to feed left to right -- that's what I would prefer to do. I'll give the G92 a try tomorrow. Thanks for the help.

[Donkey Hotey]

Hey, I'm a nOOb at this stuff but can you just reverse the threading direction but use the same tool and conventional spindle rotation?

IOW: thread toward the tailstock instead of the chuck (changing the Z direction to negative?).

[Geof]

Originally Posted by Donkey Hotey Hey, I'm a nOOb at this stuff but can you just reverse the threading direction but use the same tool and conventional spindle rotation? IOW: thread toward the tailstock instead of the chuck (changing the Z direction to negative?).

Yes, but it is best to machine a relief at the starting end so the tool has space to enter the cut and get up to synchronization with the spindle rotation.