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IndustryArena Forum > General Maintenance > BallScrew Repair > How are you supposed to hold the ball screw and tighten the nut to spec on these?
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  1. #1
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    How are you supposed to hold the ball screw and tighten the nut to spec on these?

    I got my ball screws rebuilt and new support bearings. $$$

    Now I need to put this stuff back together carefully and tighten the nuts that go against the support bearings to spec.

    I cannot find any tools to fit this stuff or hold a smooth shaft, So I am not sure what specialty tools they expect you to have? There are no flats on the screw or hex holes or anything.

    If you were to make a socket to fit the nut holes, then you still have the issue of no where to hold the screw.

    Of course there are no flats on the nut either. The nut has the holes that look like they are for a spanner, but I could not break these loose with a 2 pin spanner for anything when I was trying to remove them. The holes are messed up a bit too from people trying to adjust out backlash (when it needed rework, not a tighter nut). The nuts were likely over torqued on the original bearings. I took them off with the edge of an air hammer bit that fit in the holes. They did not come off easy at all. I even tried to clamp the oldham on before doing that method, then use something in the slot to hold it and then put a pipe wrench on the nut. It still wouldn't budge before the compression fitting of the oldham would slip!

    One of the nuts now has marks on the OD from the pipe wrench, but I can turn those off real quick for looks. The important part of the nut is perfect where it touches the inner races and the threads.

    Looking for some suggestions. I have some ideas, but none of them are quick and simple. Why they made this so hard....who knows. I see videos on new stuff and they have hex holes in the ends, or hex on the OD, or flats on the threaded part of the screw inside. Would have been much easier!

    I guess I could get new nuts instead of using these? I see no one using this style though on anything new. It seems like all the new ones have flats and brass tip set screws instead of a pinch style and they seem to use a spacer between the nut and the inner race (but this could just be to accommodate a wiper which mine does not have). I would still be left with how to hold the screw though.

  2. #2

    Re: How are you supposed to hold the ball screw and tighten the nut to spec on these?

    Well, I guess I would make an aluminum split collar about 4 inches long, bored to fit the screw OD, and bolt it onto the ballscrew wherever is convenient, maybe about three 3/8 bolts down each side. Put a pipe wrench on the collar and brace is against something solid. Probably want to do this near the ball nut so you are only putting torsional torque on the ball screw. Don't want to wrack the ball screw to the side.

    For the nut, either make a pin spanner to fit, or make new or modify the nut to your spec.

    From the drawings it looks like if you removed the motor mount and the two large bolts holding the ''bearing can'' in place, the whole assembly would slide out the back and you could do the whole set up on the bench. That is most likely what I would do. Easier than working with limited space.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Re: How are you supposed to hold the ball screw and tighten the nut to spec on these?

    I am a bit paranoid about clamping anything to the screw portion that I just paid so much to have redone.
    Everything is easy to get to. So limiting space is not really an issue. Getting the part off that the nut mounts to under the bed mill would not be fun, but I suppose the support end could be put together on the bench. I think I would rather tighten things down in position since it is no issue to get to though. The motor mount stuff can be left off, so it is pretty wide open. The Y motor is on the front of the mill and the X is just on the left of the bed.

    A few ideas I had:

    Replace the nut with a newer style that has flats and brass tip set screws.
    Then do something like you mention except clamp it on where the coupler goes.
    Hold it with the clamp where the coupler goes and then use a crows foot on a torque wrench at a 90 on the nut to torque it.
    I might have to leave one of the bolts out of the plate that holds the outer race of the bearings though so it is not in the way

    Another idea was to also replace the nut as mentioned above, but buy or make a split collar. Split a socket to mate with the split collar and weld it . Then you could basically clamp the socket onto the ball screw where the coupler goes and just hold the nut. Then, use the torque wrench on the homemade split clamp socket to turn the screw rather than the nut.

    A third idea could be to buy a new nut, then just clamp the coupler I have onto the shaft and hold it, then tighten the nut with a crows foot at a 90 with the torque wrench. This would not require me to make anything.

    A fourth idea would be to put flats on my current nut and do something like above.

    If I do anything to tighten the nut using the spanner holes, then that means I do have to likely hold the screw on the threaded side somewhere. Also, if there are no flats you can never recheck the torque or do anything without taking it all apart which includes using a puller to get the coupler off. Nothing worthwhile will fit between the nut and the coupler to get in the spanner holes. If the nut has flats then you can just hold the coupler to check torque at any time. I am not sure it will ever need to be checked, but it seems like this smooth nut with spanner holes is kind of a pain compared to one with flats and set screws. Also, you cannot get an allen in there to loosen the hex bolt on the split, so I would have to use some kind of a cap screw with a small head or something.

    I have no mill at the moment either, so I can do most things, but no milling of a custom tool....

  4. #4
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    Re: How are you supposed to hold the ball screw and tighten the nut to spec on these?

    I use one way bearing wrench, similar to ones on link to hold the screw from the floating end.

    https://www.bigkaiser.com/en/product.../mega-wrenches

  5. #5
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    Re: How are you supposed to hold the ball screw and tighten the nut to spec on these?

    Quote Originally Posted by jkkmobile View Post
    I use one way bearing wrench, similar to ones on link to hold the screw from the floating end.

    https://www.bigkaiser.com/en/product.../mega-wrenches
    Interesting. It does not look like they make a 28mm one though.

  6. #6
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    Re: How are you supposed to hold the ball screw and tighten the nut to spec on these?

    You can make one.. just buy a 28mm one way bearing and mill a handle. Locktite or glue the bearing in it..

  7. #7
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    Re: How are you supposed to hold the ball screw and tighten the nut to spec on these?

    the rollers in a one way bearing are hard hard.

    like Jim said you need to make a aluminum split collar to clamp on the screw.

    And a pin drive socket.

    most importantly and urgently you need a friend with a Bridgeport and a lathe.

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