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Thread: Telescoping cross slide lead screw problem

  1. #1

    Telescoping cross slide lead screw problem

    Hi All,
    My Rockwell 25-700 has a taper attachment with a telescoping cross slide lead screw. There is a nut that secures the lead screw to the taper attachment. The pencil is pointing at it in this picture.


    I want to tighten the nut as much as possible to minimize backlash but when I do the nut binds while turning the lead screw. Then when I back the lead screw off, the nut loosens or sometimes comes off. How are telescopic lead screw normally attached? Is this a factory install?

    Anyone have an idea how to prevent the binding and backing off of the nut?

  2. #2
    Senior Member caster's Avatar
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    Hi KDude, I don't have a taper attachment on my lathe but as I understand taper attachments the cross slide is disconnected from the leadscrew, the leadscrew is removed and the cross slide is connected to the taper attachment. As the carriage moves to and from the chuck the taper attachment moves the cross slide it in and out creating a taper.

    Hope this helps,

    Caster

  3. #3
    Appreciate the reply Caster.
    With a telescoping lead screw you don't have to disconnect anything because the lead screw is in two pieces and extends as the taper changes. My particular lathe has a nine sided straight spline that telescopes as shown in these pictures.


  4. #4
    Senior Member caster's Avatar
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    If the cross slide is connected to the taper attachment wouldn't you use the compound to move the cutting tool?

  5. #5
    hmmm, how do I explain this ...
    I'm not trying to cut a taper. The taper attachment is set parallel to the ways. If I want to face off a piece of metal using the cross slide, the nut binds and loosens as previous mentioned.
    Somewhere on the vast internet, I thought there was an article showing how to replace the nut with a ball set in some type of "V" block. That way the lead screw could still spin, but would be secured to the taper attachment side while allowing for the travel in the splined lead screw.

    I'm not sure how clear I was on this ^^.

    Think I'll go try slipping a flat washer between the nut and brass and add some grease.

  6. #6
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    You need a jam nut. There should be two nuts. You snug the inner one down and then make it hold it's position by jamming it with another. "Jam" them together and they won't loosen/tighten while spinning the lead screw.
    FLAME ON...!!!!

  7. #7
    Senior Member Robert's Avatar
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    In the pic it doesn't look like enough room for a jamb nut? Sounds like it would work though.
    R
    "Whether you think that you can, or that you can't, you are usually right."
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  8. #8
    Correct, there is no room for a jam nut. The nut that is on there look like it was cut in half to be thinner because there is a burr to one side.

    I tried some grease and that made it worse. The nut spun off so easy. So I cleaned up the nut and treads real good and put it on dry. In the process I removed a washer. It seems to be tight and not binding now. My guess is the washer was keeping the nut from bottoming out on threads and bottoming out the threads seems to be holding it in place.

    Time to cut some chips and see how it works!

  9. #9
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    hmm... So there isn't enough room for a jam nut and the current nut seems to be modified... I'm willing to bet what you have isn't original and a previous owner put on what is there because he lost the originals.

    A quick google search revealed pics of the south bend taper cross screw utilizing two jam nuts. I doubt your Rockwell reinvented this wheel.

    Other options would be fab'ing in provisions for a grub screw in the nut you have to retain it's position. ...or using a little Loctite.
    FLAME ON...!!!!

  10. #10
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    Locktite is the way to go.

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