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Thread: Lathe half nut adjustment

  1. #1

    Post Lathe half nut adjustment

    Requesting help on a procedure for adjusting the half nut on a lathe.

    The Engagement lever will sometimes only go about half way. Sometimes it will engage the lead screw correctly.

    There are two set screws, and, I think two small bolts that serve to adjust the half nut. The lathe is a 12x37 grizzly, two weeks old. The manual does not have a procedure for adjusting the half nut.



  2. #2
    Join Date
    Dec 2002


    I would adjust it closed on the leadscrew, then back it off maybe 1/4 turn. Sounds like something is wrong with it working sometimes and sometimes not. There may be a cam in the mechanism and could be something lose that sometimes blocks movement. Might have to drop the apron to find out.

  3. #3
    Join Date
    Jan 2004


    Now, then, I'm wondering if you have a thread dial?

    Adjusting, well maybe. But if it sometimes closes right, it must be set up to fit the thread OK. The difference is whether the thread is ready under it when you go to close it.

    That is where the thread dial comes in, to tell you when you can close it. When a mark is on the line, you should be able to close. If not, there is a problem with the dial. Maybe THAT needs adjustment?

    Keep eye on ball.
    Hashim Khan

  4. #4


    I will follow both suggestions. Thanks. Another quick question.

    Is the "normal" half nut adjustment for wear (up and down on the lead screw) or is it for lateral adjustment on the lead screw?

    The parts pictorial in the users manual are dificult to figure out.


  5. #5
    Join Date
    Apr 2001


    I suspect "problem" is just that the leadscrew thread isn't lined up with the halfnuts thread when the halfnuts won't close. When this happens again, keep pressure on the lever and turn the leadscrew maybe 1/2 turn and see if the lever drops into place.
    Try to make a living, not a killing. -- Utah Phillips
    Don't believe everything you know. -- Bumper sticker
    Everybody is ignorant, only on different subjects. -- Will Rogers
    There are lots of people who mistake their imagination for their memory. - Josh Billings
    Law of Logical Argument - Anything is possible if you don't know what you are talking about.

  6. #6
    Join Date
    Apr 2003


    As long as the halfnuts drop all the way in with the leadscrew turning,nothing is wrong. If the leadscrew is not turning, there is only about a 50-50 chance that the halfnuts will drop in with the carriage at any random position. If they wont drop in, move the carriage slightly, and if they drop in then, again there is nothing wrong.

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