"Harold & Susan Vordos" wrote in message ...
"Vincent Coppola" wrote in message
om...
snip------

Actually I think I had the compound set wrong. To start with, my
threading tool is made from drill rod. I got the idea from the 7x10
minilathe post on yahoo some time ago. Anyway the suggestion was to
get the same size rod as my boring tool holder, in my case 3/8" and
then turn a disk on one end. Make it a 60 degree angle on each
shoulder. Then grind off the top and bottom of the disk to form two
cutting tools. This is what I have been using.

There's nothing wrong with that if you know how to properly grind the
necessary relief angles after you've formed the 60 degree sides, and you can
drop the bar such that the top of the tool is on center. Any variation
from center height, or alteration of the top of the tool from dead flat and
parallel to the ways will yield an altered thread form. It's always a very
good idea to never touch the top of a threading tool, no matter what you
hear some of the "experts" say. When you grind a rake angle, the back
side of the tool will generally no longer make contact with the thread, so
the thread doesn't get cleaned up, nor does it conform to the threading
tool, instead taking the angle of the setting of the compound.

Now as far as the
compound angle goes I don't have a handle like you say. Picture it
this way....I shrink myself and stand on the tailstock. I then peer
straight into the headstock. Let's call this 0 degrees. I point the
boring bar in this direction. Now I turn it 30 degrees
counterclockwise. I then feed toward the headstock. I just tried this
and the thread looks much better. Must have done something right. How
does this sound?


Not good! Not if I understand what you're saying, anyway. If you have a
compound, it must have a handle of sorts, and it is that handle that you use
to feed the threading tool on successive passes, after setting the cross
slide to 0. The boring bar itself should parallel the ways of the machine,
assuming the cutting portion is at right angles to the shank of the boring
bar. The way you've described your setup, you have turned the threading
tool 30 degrees. Only the compound should be turned the 30 (actually only
29) degrees, which you'd do before setting up the threading tool. When the
threading tool is properly set, the angle of the thread, 60 degrees, is
equally split on each side of the tool, so the sides of the thread are each
30 degrees as they relate to the cross slide. What's important is that
you feed the tool at slightly less than the half angle of the thread.
Anything more simply cuts away the back side. When you set up your
compound properly, almost all off each pass takes the material off the
forward edge of the material, where the lead screw keeps the tool in
intimate contact with the cut. That not only guarantees the proper lead, but
permits superior chip flow, which can be a serious problem when threading
coarse threads in tough materials. Aluminum is usually pretty forgiving,
as is leaded brass.

If you're still not clear on this, lets keep talking. Threading, in order
to be right, must be approached properly. We'll get you there, just keep
asking questions. If you can post a picture of your setup it would help a
lot! That way we'd get past differences in descriptions.

Harold


Harold,
Ok I think I get how to set the compound angle now. Had to look at the
manual. I found the screws to loosen.(Yey) Ok, picture this...a clock
face. The headstock is at 12o'clock, the tailstock is at 6 o'clock, I
am at 9 o'clock. The angle on the dial reads 0 degrees. OK now I
turned the compound counterclockwise until my dial reads 29 degrees,
the compound moved from 12 o'clock to approx. 10 o'clock. I had to
turn the boring bar clockwise to compensate and get it back to 12
o'clock or parallel to the ways. This is probably opposite to what you
told me before.

Wait, now I took another look at it...Now it makes no sense this way
either. If I turn the tool holder to compensate for the angle I turned
the compound, when I engage the leadscrew the tool is moving at the
same speed and in the same direction. The only difference is when I
turn the compound rest crank, the tool moves at an angle and I can see
now how to make a bevel. Still can't see what difference it would make
for making a thread unless there is a force vector against the thread
changing somehow. Can't see how any angle would change on the thread
unless I manually turn the compound rest while the leadscrew is
turning. There that was confusing!
I think the best thing to do is take a picture and email it to you.


Vince