"Ken Grunke" wrote in message
...
gglines wrote:
http://www.metalworking.com/DropBox/...ding_setup.pdf

I don't cut internal threads that often (usually tap), but when I do,
it takes me forever to remember how to set the lathe up correctly.
There was an excellent discussion on this topic on the Chaski Board
recently.

I made this chart which I've uploaded to the metalworking.com drop box.
Harold Vordos graciously corrected all my mistakes and as always, I
appreciate his willingness and ability to teach the craft so well.
Hopefully, this will help someone else.



George,

There are two more positions as alternates for starting inside the hole
and coming out, which is not a fun thing to do.
They are both for the back side of the hole, with feed to the left:

RH with the tool down, forward rotation.
LH with the tool up, in reverse.

In both cases, the compound is aligned the same as for RH external
threads, pointing to the left--I would call it going from 5 o'clock to
11 o'clock, generally the most convenient position.

You can cut RH, LH, internal and external with the compound in this
position--just flip the toolbit appropriately.

So it's always the left side of the cutter doing the chip removal, and
the right side is just taking an extremely fine shaving as the tool is
fed in a half a degree more to the right than straight along the
thread's left flank.

Ken Grunke

Threading as you suggest is not a good idea. The pressure of the cut has
the ability to propel the carriage ahead of the lead screw, causing a
drunken thread. Feed of the compound should *always* be in the same
direction as the cut, which avoids the problem by loading the cut against
the lead screw. That is, and has always been, the reason for setting the
compound on different sides, depending on the nature of the thread involved.

Harold