ER 32 COLLET HOLDER VIDEO PART 2

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BillTodd:

--- Quote from: andyf on April 04, 2013, 05:52:55 AM ---Another great production from Doubleboost Studios, John.

One thing I'm :scratch: about, though. At about 15:30 in, you show the topslide angled at 29°, but it looks to be at that angle from the lathe bed, and so at 61° from a line perpendicular to the bed. Is that right? I’ve only had one cup of coffee so far this morning, so may be missing something.

Andy

--- End quote ---

Looks wrong to me :(

The top-slide should be set at about the same angle as the V of the thread (the exact angle is subject to debate)

Imagine a straight edge placed against the V of the thread you are about to cut , your top-slide should move parallel with this line.

For a RH inside thread the angle is / (same as a LH OD thread) . The idea, is that the tool is advanced in the same direction as the flank of the thread (with a tiny clearance), which reduces the loading on the tool because it is only cutting with one edge and gives better swarf clearance .

Now that said, if , at the end of the day, if you take a final pass or two using just the cross-slide (i.e. so the tool cuts on both edges - acting like a form tool ) then the thread will end up the correct profile

Top slide angle = ~ thread V angle
for Internal RH /
for External RH \
for Internal LH \
for External LH /

Bill

hopefuldave:
Bill beat me to it! I reckon the topslide's at the wrong angle, too... Another 30 degrees anticlockwise would br right, then the 'back' edge of the tool will follow the thread trailing flank. Jommetry, ain't it?
As Bill says, a final cut or three with the cross-slide will probably sort it out, as long as you're not.too close to.the major diameter... I normally take a 'straight in' cut or three for the last few thou" to clean up both flanks and ensure the right thread form.

Otherwise, great video, John!

Dave H. (the other one)

andyf:
I’m no expert on screwcutting, Stuart, but I have done a fair amount of it, including internal threads, with the topslide set at an angle of 29 deg. to the side of the cross slide, not the lathe bed. Looking from the front, its handle was pointing at roughly 1 o’clock

Had I set it at 29 deg. to the lathe bed, it would have produced an asymmetric thread, the leading flank of the tool producing the correct angle on the thread flank it was cutting, but the tip of the tool leaving the other flank at far too shallow an angle to the longitudinal axis of the work.

I agree with Bill; it looks wrong, but no doubt John will put us right!

Andy

doubleboost:
The angle of my compound slide is wrong
The last few cuts were taken straight in this cleaned the thread up fine
(we have been hear before)
It depends where you measure the angle
John

porker:
Great videos.These really fill the "gap" for me - someone who is interested in this as a hobby but has no background in this and does not know anyone who does personally. Books are great as far as they go but seeing someone actually doing it is very useful. I also like the pace and the style. :beer:

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