I am reading various sources for information on threading in the
lathe. A lot is said about external threads, but not near as much
about internal threading.

For the moment, I am interested in cutting right-hand internal v
threads.

Various sources say to turn the compound 29.5 - 30 degrees to the
left. Disadvantage: No room to enter hole. Or leave compound to the
right and turn tool upside down. Or put compound in rear right
corner. Disadvantage: Have to lean over lathe to adjust. Other
permutations of these exist when the lathe is run backwards.
Disadvantage: Danger of unscrewing the chuck.

Why can't you just leave the compound set the same way as when cutting
external threads (29.5-30 to the right) with the tool in the normal
right side up position? The tool is still only going to cut on one
side. This time it will be mostly cutting on the rear side of the
tool and not the front as when cutting external threads.

Any thoughts would be greatly appreciated. Thank You



With the feed going the same way as the pressure from the cut, the tool may
tend to jump ahead a bit. Better to have the feed forcing the tool into the
cut.

The easiest way to thread is with a cross slide stop, but the only way you can
use one while internal threading is if you cut on the far side of the axis,
whether upside down or right side up.

John Martin