Jerry, here’s where I can attempt to teach the teacher. There’s two ways that I have turned left handed threads on a lathe. The first is to cut a relief where the thread ends, to the depth of thread. In other words, if the length of thread that you want is 2”, thats where the relief will be cut. I usually use a cutoff tool that has been radius’s or a tool bit thats ground similar. Then thread as usual starting at the relief with the carriage feed going away from the the head stock.
The second method is to turn the tool bit upside down, reverse the direction that the lathe is normally running, then thread as usual. This method is not the preferred way, because the force is trying to pull the tool up away from the holder and cross slide which goes against the way the lathe is designed. As long as you are only using it for small threads, it works really well.
If your expertise is beyond these methods, I humbly apologize for trying to teach the master and take my seat.
Last edited by Phak1; 11/04/2019 1:38 AM.
