Anatol
Aluminum
- Joined
- Jan 19, 2018
- Location
- Los Angeles
FYI - found on youtube
Old Southbend instructional movie taper.mp4(360p_H.264-AAC).mp4 - YouTube
Old Southbend instructional movie taper.mp4(360p_H.264-AAC).mp4 - YouTube
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Newtons third law, "For every action there's an equal and opposite reaction". For machine tools you'd subtract that reaction from the machines own mass, rigidity and resistance to those forces. Once you do understand everything we have or use is in one form or another basically rubber you can then start to appreciate why machines require minute adjustments to help compensate and offset those forces. Trying to exactly duplicate a taper using a test indicator against an already known taper such as a Morse Taper on the top slide or taper turning attachment only gets you fairly close. The lathes own non optional clearances and rigidity are always working against us.
Even if you could somehow preset the angle to millionth's of an inch in accuracy it would still be wrong under those actual cutting loads and conditions as those clearances and machine tool part deflections are taken up. Visualize the necessary few thou clearances between the two halves of the top slide dovetails. As there taken up under those cutting loads the slide will take a slightly different angle as the end closest to the cutting tool is jammed against the dovetail and the other end pivots in the opposite direction. The same to a lesser amount because the parts are a bit more rigid happens with the taper turning attachment as well. It's also why light finishing cuts are more accurate because the cutting loads and machine deflections are much less. It's also why cutting a male and female taper using the exact same top slide angle still won't perfectly match each other because generally the cutting forces are acting in opposite directions on the top slide as each taper is cut. Using the cutting tool upside down and cutting on the back side of the female taper can help duplicate the same loads as what happened while cutting the male taper. It's simple physics, but not quite as obvious as it would seem because it's happening at levels that can't easily be observed.
@Anatol: Thank you very much for sharing this! I have seen very little info on use of a taper attachment.
I have a SB 13" lathe with the taper attachment. I have used it one time and it worked nicely, but I still have many questions. I don't have a good understanding of how the taper attachment controls the cross feed in place of the lead-screw. In the video, he removes a screw that should release the lead screw nut, but when I take out a similar screw in my lathe, the nut is still attached. So this mechanism is still mysterious to me. My lathe is a mid-70's machine.
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