ER 32 COLLET HOLDER VIDEO PART 2

[doubleboost]

John

[Sid_Vicious]

Thank You Sir...We have Waited for part 2.  I really like your videos.

[Swarfing]

John we still need to know does she come back for the baby or what 

Good job 

[krv3000]

as per well dun

[vtsteam]

Excellent practical videos! 

[Brass_Machine]

Nice job John. I especially liked the back view as you were cutting the threads.

Eric

[lordedmond]

Very good Video and well explained as usual John

You are as good at video editing as you are at metal working


thanks again

Stuart

[andyf]

Another great production from Doubleboost Studios, John.

One thing I'm  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

[S. Heslop]

Nice video. Looking forward to part 3.

[lordedmond]

Andy

think of the thread form its in this case a 60 deg form as a apposed to the whitworth form of 55 deg

look at a large bolt the compound is set to the flank angle so that the tool runs down the flank and therefor cuts on only one side

the 29 angle is not half of the thread form but is off slightly to stop the tool rubbing on the uncut flank


the compound would be round the other way ire forward of the lathe centre line to cut an external thread


took me a long time and many circuits around the sun to get my head round it


But is there not always, if you use a preformed form tool to cut the thread ( insert tool ) you go straight in at 90 deg because the tool forms the root and crest , as John shows in his getting screwed video in which he shows the cutting of a lead screw and nut


Stuart

[BillTodd]

Another great production from Doubleboost Studios, John.

One thing I'm  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

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. 

[micktoon]

Another good Video John  , As Porker says , just what you need when you are not froma machining background , watching the job getting done is like reading ten books and more ................... keep up the good work John , Looking forward to part 3

 Cheers Mick

[Fredbare]

Great video John, like others on this forum i am new to this, and your videos are so informative, many thanks.

John