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Thread: threading on jet 9x20 lathe

  1. #11
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    Dec 2015
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    Chilliwack, BC, Canada
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    Yep, I've done both styles of ending the thread.

    One method is a runout like shown where you pull back the cross slide then shut off the lathe or disengage the half nuts. It produces a long tapering runout of the thread as shown. Or it can be as abrupt a ramp out as a 1/3 to 1/2 turn of the part and thread. Depends on a lot of things and some small amount of practice where you run the lathe in threading mode but don't actually make a cut a few times but have a mark on the part so you have a target of where to run out then pull the half nuts. At 130 RPM it does not need to be all that rushed either. You still want to do the actions smartly but it doesn't need to be lightning quick either. And as mentioned if you're doing the threads at something like 16 TPI or finer it gives you more time.

    The other way is a relief groove as shown by Paul above. When I do a relief groove I like to make them about 1.5 to 2 threads wide or even more if I have the room. Otherwise I'll go for a single thread groove and use an extra slow back gear speed. That way I've got a decent sized target and if I'm out by a touch it will still stop in the groove. The nice thing about a relief groove is that we don't need to do 2 things more or less at once. With the taper out we have to back off the cross slide wheel then disengage the half nut. With the relief groove we simply have to open the half nuts on cue then breath again.;0

    If you're doing a fairly short thread and it's only 4 or 5 turns a trick you can use is to engage the half nuts with the cutter well off the work. Like set it up a good half or one inch out. This will give you a few seconds to get the half nuts engaged and get in synch with the pace of the travel. After all there's TWO specific targets we need to hit. The first is to engage the half nuts right on one of the threading index dial's marks. Then we need to disengage in the groove. It takes a moment after the engaging to shift mental gears and get ready for the disengage. Starting up the cut with some time wasting air cutting gives us a couple of precious seconds to get the shift in focus smoothly.

    It won't take long before you find yourself using less and less wasted time by starting the passes well off the part. But it's good to make up some threaded things ahead of time that do not rely on really tight timing such as threading up to a shoulder. But do mark off a target length for the threading so you're working to a limit instead of just free practicing. It's good to impose the limit so you learn more and get the feel for ending the thread where and how you want it to end.

  2. #12
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    Mar 2015
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    Another good way to end a thread is to post something political, religious, or racist.

  3. #13
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    Quote Originally Posted by RB211 View Post
    Another good way to end a thread is to post something political, religious, or racist.
    Was this thread not derailed enough to be worth of HSM? Just wondering where your comment came from? It's by far the most on topic thread running at the moment.... up to now of course.

  4. #14
    Join Date
    Mar 2005
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    St. Louis Metro area
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    Quote Originally Posted by RB211 View Post
    Another good way to end a thread is to post something political, religious, or racist.
    Wow, you should probably head back to facebook....
    Feel free to put me on ignore....

  5. #15
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    Huntsville Ala
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    ...looks like we have in our midst a distinguished graduate of the 3 phase light bulb school of forum etiquette.

    I've always preferred to set up travel indicator on a Mighty Mag base, attached to the ways to start reading about .100 before my target end point. That gives plenty of time to get ready to wind out the X-feed and release the half nuts. Of course it helps that my lathe can be slowed down to 25 rpm too.

  6. #16
    Join Date
    Oct 2013
    Location
    USA MD 21030
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    Maybe a good shop project would be a limit switch to turn off the lathe motor and stop carriage travel when it gets close to the chuck or the tool goes past a safe place on the work. Some ideas:

    http://www.opensourcemachinetools.or...mit-switch.pdf

    http://www.chaski.org/homemachinist/...ic.php?t=95191

    http://bbs.homeshopmachinist.net/arc...p/t-62726.html

    https://www.youtube.com/watch?v=rY6YHA4upRU (mechanical release)

    (electrical stop with a DC brake motor)

    Most lathes with induction motors won't stop quickly when power is removed. But it might be possible to rig a mechanical clutch or brake that will stop the spindle faster.

  7. #17
    Join Date
    Dec 2007
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    This is my favorite set up, would love to have one. https://m.youtube.com/watch?v=sn8av4Y1crU

  8. #18
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    Mar 2015
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    Put the threading tool upside down and back of the workpiece, reverse the spindle direction, and turn a thread going away from the headstock. No more danger of crashing. See? Thread isn't derailed...

  9. #19
    Join Date
    Feb 2012
    Location
    yuma az
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    110

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    Quote Originally Posted by RB211 View Post
    Another good way to end a thread is to post something political, religious, or racist.
    Lol guess I'm the only asshole that chuckled

  10. #20
    Join Date
    Jan 2014
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    Long Island, N.Y.
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    Quote Originally Posted by RB211 View Post
    Put the threading tool upside down and back of the workpiece, reverse the spindle direction, and turn a thread going away from the headstock. No more danger of crashing. See? Thread isn't derailed...
    You got 2 out of 3 right. Either turn the tool upside down or move it to the back of the workpiece, not both.

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