5524
« on: October 24, 2009, 01:58:29 PM »
ART,
Well, first let me say that I am glad someone else is trying the the threading out.
The M1.5P ( 1.5x.0394=.0591" ) is close to the 20TPI i was running. Additionaly you get some
other uneven numbers in there like .xx91 for a pitch value. And we know that a small difference in
the defined pitch will change lead.
A nice new tap is a good compare against the thread as they are ground very accurately. I will
assume it was a ground tap. Most of mine are for H2, which simply means the diameter on it is held to
provide a tolerance of 0.001" over the basic pitch diameter.
Almost all of my threading has been done with averaging on
If averaging is on then all the rpm reported would be averaged and that is the value that would be
used for the NEXT thread pass. Correct?
If averaging was off then assume that the last reported...Or.... is it the requested used?
Unconfuse me.
I have not remarked much on what you see at the end of the thread. ie; single, double / multiple
lines.
I have used the distance in spacing to reaffirm what i thought i observed during the threading. (ie; a
later pass increases the thread) You would think that the difference between the ending of those
scribes could be used for lead error, or maybe tiiming pulse, rpm....but.... i figured if you have
some runout on the diameter of the piece or a difference of velocity as it pulls out of the thread,
backlash as it changes direction on pullout.....just too many variables to try and make sense of
what that measurement is telling you. SO i just use it as a visual.
I need to remark that no variable speed drive or whatever is used here just a plain good old
fashioned motor.
AVERAGING
If you get a change of speed, a practical example would be while threading and you hit a hard
spot in the metal, or, say you catch material just as the cutter hits the material at the beginning of
the thread, if that value was very influential on the next to last pass, then a good thread
can be ruined if averaging was off . If on, the affect would not be as great. Actualy calculated
forces can easily double.
Now if your in the middle of all the passes, there is recovery, by the additional passes yet to be
done. But then, if it was spring in the material or poor setup, then who knows!
The point is, the mechanical apsects of threading can vary the situation.
Like you, i am not sure what to make of it.
I won't even get into the acceleration and deceleration part of the cycle. I will say that whatever
someone does to test, keep the pullout at the same angle and use a common value like 2 or 3
times the pitch for free cutting before the actual thread is engaged by the cutter.
RICH
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