"Ken Grunke" wrote in message
...
Harold & Susan Vordos wrote:
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
If I understand you correctly, you're referring to the pressure on the
right side of the cutter which is taking only a minute (myNOOT) shaving?
It can't be very much, if you're advancing the compound only a little
for each pass as generally recommended.
Are you saying that the compound should be set at 30 degrees, instead of
29.5?
In my suggestion, the compound is *always* fed in the direction of cut,
it's just set a half degree in from 30 degrees. The advancement into the
left flank of the thread is so miniscule at that angle, that it barely
cuts on that side.
Ken Grunke
I'm sorry, I apologize. When I re-read your original post, I realize I
misinterpreted your comments as threading from the inside to the outside
(that was on my mind). *You clearly stated the opposite.* The two methods
suggested are, indeed, proper, but I would hesitate to use them unless I was
threading a through thread.
I would take exception to your statement about the difficulty of threading
from the inside to the outside. My first attempts to do it were a result
of the horrible difficulty of threading to a shoulder when chasing a 1"-8
inside thread. The bore was deep, near two inches. It was far easier to
start the thread in the relief that was permitted than it was to pull the
half nuts at the precise moment when threading such a course thread. I
guess it's all in what one gets used to! g
Harold
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