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IndustryArena Forum > General Maintenance > BallScrew Repair > Double Ball Nut Spacer Problem
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  1. #1

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    Double Ball Nut Spacer Problem

    Hello everyone,
    I'm very new to cnc
    I'm trying to put the ball nut on a screw, but I cannot make the spacer ring tightened between the nut's halves. Now it looks like the spacer is not doing anything? I think it must be tight between the halves. I
    Am I missing something? I have the same problem with 3 nuts. The nuts are 2005.
    Thanks in advance
    Regards,
    Vilyo

  2. #2
    Community Moderator Jim Dawson's Avatar
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    Re: Double Ball Nut Spacer Problem

    Looks like you need some shims or a thinner spacer. Looks like that is not quite a finished system.

    Or you could make a screw adjustable system that would preload the nuts.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
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    Re: Double Ball Nut Spacer Problem

    Quote Originally Posted by Vilyoo View Post
    Hello everyone,
    I'm very new to cnc
    I'm trying to put the ball nut on a screw, but I cannot make the spacer ring tightened between the nut's halves. Now it looks like the spacer is not doing anything? I think it must be tight between the halves. I
    Am I missing something? I have the same problem with 3 nuts. The nuts are 2005.
    Thanks in advance
    Regards,
    Vilyo
    There should be no gap between the Spacer they are ground to the correct thickness this will give you the correct preload when you assemble it correctly

    Don't mix up the spacers they may be different for each assembly
    Attached Thumbnails Attached Thumbnails Double Nut.PNG  
    Mactec54

  4. #4
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    Re: Double Ball Nut Spacer Problem

    Quote Originally Posted by Vilyoo View Post
    Hello everyone,
    I'm very new to cnc
    I'm trying to put the ball nut on a screw, but I cannot make the spacer ring tightened between the nut's halves. Now it looks like the spacer is not doing anything? I think it must be tight between the halves. I
    Am I missing something? I have the same problem with 3 nuts. The nuts are 2005.
    Thanks in advance
    Regards,
    Vilyo

    How did they arrive when you bought them?. Were they seperates ie: not pre-fitted to the screws?.
    You've either mixed them up or manuf didn't bother checking preloads.
    Either way, That's a damn large distance.

    You can either try to shim them out or, leave nuts on without the bars- slide spacers out- skim down spacers a little at a time- test fitting as you go until you get thereabouts.
    A minor discrepancy can be dealt with a lot easier than a large one afaic using alu foil.

  5. #5

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    Re: Double Ball Nut Spacer Problem

    The nut arrived with a plastic cylinder inside it. When I try to move it on the screw the gap appeared. there is always 2mm gap between the spacer and the nut
    Attached Thumbnails Attached Thumbnails 232702199_539515347259201_2967558959906445791_n.jpg   233918643_795262561144890_6564812868673013835_n.jpg   235033583_344124444039178_618886292246528533_n.jpg   236139760_142438044702078_6534532022724568933_n.jpg  


  6. #6

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    It seems that the spacer is a bit bigger than it should be.
    If I make the spacer 5.76mm thick I guess it will be fine? What do u think? The spacer is 6.33mm now
    Attached Thumbnails Attached Thumbnails 20210814_160242.jpg   20210814_160233.jpg  

  7. #7
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    Re: Double Ball Nut Spacer Problem

    Quote Originally Posted by Vilyoo View Post
    It seems that the spacer is a bit bigger than it should be.
    If I make the spacer 5.76mm thick I guess it will be fine? What do u think? The spacer is 6.33mm now
    it should be bigger than the gap this is how the preload is done, the measuring you are doing is not very accurate with a digital caliper it does seem to be bigger than it should be but should be bigger than the gap

    With the 2 nuts mounted try and squeeze the spacer in between to see if it can fit, the correct way would be to remove the 2 keys, assemble with the spacer then rotate the nut into position and put the 2 keys back in place

    Contact the seller before you do anything, the spacer would have to be Ground on a surface grinder if it needs any machining
    Mactec54

  8. #8

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    Quote Originally Posted by mactec54 View Post
    it should be bigger than the gap this is how the preload is done, the measuring you are doing is not very accurate with a digital caliper it does seem to be bigger than it should be but should be bigger than the gap

    With the 2 nuts mounted try and squeeze the spacer in between to see if it can fit, the correct way would be to remove the 2 keys, assemble with the spacer then rotate the nut into position and put the 2 keys back in place

    Contact the seller before you do anything, the spacer would have to be Ground on a surface grinder if it needs any machining
    I cant tighten the nuts more than that.
    Attached Thumbnails Attached Thumbnails 20210814_190204.jpg  

  9. #9
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    Re: Double Ball Nut Spacer Problem

    Quote Originally Posted by Vilyoo View Post
    I cant tighten the nuts more than that.
    Show this to the seller ,does each Ballnut have the spacer it came with as this is the normal way to assemble them

    Are all your spacers the same thickness with a rough measurement, if not they may be mixed up and you have to add a thinner one on this screw, it would not have to be much different in thickness to be in the right position
    Mactec54

  10. #10

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    Re: Double Ball Nut Spacer Problem

    the nuts came with original package and were with the keys assembled. All spacers are the same thickness. The best solution might be to reduce the thickness of the current spacers..

  11. #11
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    Re: Double Ball Nut Spacer Problem

    Quote Originally Posted by Vilyoo View Post
    the nuts came with original package and were with the keys assembled. All spacers are the same thickness. The best solution might be to reduce the thickness of the current spacers..
    The first thing would be to contact the supplier we may be missing something, some of these cheaper Ballscrews have a Belleville washer to do the preload so the spacers may be ok and just missing the Belleville washer there are lots of different way they do this type of Preload

    If you where to Grind the spacers they would be a lot of back and forward to get the right thickness
    Mactec54

  12. #12

    Re: Double Ball Nut Spacer Problem

    Shim it will foil until the keys line up.

  13. #13

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    Re: Double Ball Nut Spacer Problem

    yes, i guess that will be the easiest way. i hope it will work fine. need to add near 2mm between the spacer and the nuts to line up the keys

  14. #14

    Re: Double Ball Nut Spacer Problem

    Start by complaining to the seller. Especially because it's multiple parts.

    After that, feeler gages might be easier than foil given the gap. Either way, stuff some some junk in there and get it preloaded.

  15. #15

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    Re: Double Ball Nut Spacer Problem

    the seller is awful, i had many problems with my order. finally most of the problems are fixed. i will never buy again from the same seller.

  16. #16
    Community Moderator Jim Dawson's Avatar
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    Re: Double Ball Nut Spacer Problem

    The easy way is to just make a screw adjustable system. I have done this before and it works great. Allows you to exactly set the preload to your personal preference, no shimming required.

    Or buy some quality ball screws from THK, Hiwin, or Thomson.
    Jim Dawson
    Sandy, Oregon, USA

  17. #17

    Re: Double Ball Nut Spacer Problem

    Or a rubber bumper in there, takes less measuring, but also has less precise preload.

  18. #18

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    Re: Double Ball Nut Spacer Problem

    what do u mean by adjustable system? I already payed 150 euro for 3 nuts. I dont want to buy another.

  19. #19
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    Re: Double Ball Nut Spacer Problem

    Quote Originally Posted by Vilyoo View Post
    The nut arrived with a plastic cylinder inside it. When I try to move it on the screw the gap appeared. there is always 2mm gap between the spacer and the nut

    My point of view is they were never tested on a screw to match preload. Stuck some generic off the shelf spacers in.

    Show the seller the pics with them on the screws. If no response I would grind down and then fine tune with foil. Will be easier than going bigger.
    Don't take straight down to 5.76. start a bit bigger.
    I have mine loaded pretty tight using the foil method (pushing away from each other).
    I went a little far and am limited to 3000mm/min until it sounds rough but that's fine for me.


    My backlash in the nut is 0.015mm and you can feel a bit of a bite in there.
    When on the machine with stresses etc it comes out just shy of 0.03mm overall. Happy enough with that and took effort.
    Lets see how long they last.

  20. #20
    Community Moderator Jim Dawson's Avatar
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    Re: Double Ball Nut Spacer Problem

    Quote Originally Posted by Vilyoo View Post
    what do u mean by adjustable system? I already payed 150 euro for 3 nuts. I dont want to buy another.
    Design a nut/screw system to replace the spacer, just a threaded collar. Very simple to build.

    , or put an end plate on the ball nut housing and use grub screws to apply preload.

    That's what I did here, the grub screws are circled, and one more is hidden above the ball screw. Sorry I don't have a better picture.

    Jim Dawson
    Sandy, Oregon, USA

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