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Re: [mill_drill] Re: Ball screws

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  • Guenther Paul
    You can buy ball screws and nuts from McmasterCarr they have diverant finishes for them  GP ________________________________ From: jdkmlw
    Message 1 of 14 , Mar 2, 2013
      You can buy ball screws and nuts from McmasterCarr they have diverant finishes for them
       
      GP



      From: jdkmlw <Coils69@...>
      To: mill_drill@yahoogroups.com
      Sent: Sat, March 2, 2013 12:41:07 AM
      Subject: [mill_drill] Re: Ball screws

       



      --- In mill_drill@yahoogroups.com, "Larry" wrote:
      >
      > OK all I want to do is put ballscrews on my g1007. No cnc yet. I just want the ball screws. what am I looking for?
      >
      Remember ball screws have very little resistance, so you'll need to have drag on the gibs or the table will most likely move while cutting.

      I think this is a good deal.
      http://roton.com/Mating_Components.aspx?family=7059321
      I used this screw and nut (5/8" x .200") on my X & Y and made the nut mounts from aluminum. Ordered two 3' pieces and have more then enough left over for the Z. I used two of the standard nuts on each screw, four of these were still cheaper then a single anti-backlash model.

      If you want to mod the original mounts for the nuts you need the 3/4" screw and that is $10 more per foot and the nuts are $15 more each.

    • Jim S.
      You said: You can buy ball screws and nuts from McmasterCarr they have diverant finishes for them Just be careful of the ball screws on McC. While it might
      Message 2 of 14 , Mar 2, 2013
         
        You said:
         
        You can buy ball screws and nuts from McmasterCarr they have diverant finishes
        for them

        Just be careful of the ball screws on McC. While it might have changed, they used to list their ballscrews as for instance 5/8 diameter by 13/64 pitch (not .200). Thus may have been a typo, but it turned me off on using them. You can get 5/8 x .200 lead ballscrews from Rockford Ballscrew http://www.rockfordballscrew.com/ . Their rolled ballscrew had a standard precision of +/-.009 inch lead error per foot cumulative, but for a slight extra charge you can get their extra precision with a maximum lead error of +/-.003 per foot cumulative, probably just selected stock. Getting precision greater than this means going to a ground ball screw at much greater expense. The lead error can be mapped out and compensated for when tuning your controller. They also have left hand thread ballscrews if you need them. I'm sure there are other vendors, but I am familiar with them. If nothing else, their technical info is worth reading. Be aware that the above info is several years old from back when I was involved with some ballscrew work. YMMV.
         
        Another poster's remarks about using two nuts per screw works. It is much cheaper than any of the preloaded nuts sold commercially. You mount them so they can be preloaded against each other to eliminate backlash.
         
        I hope the above is of some use to the members.
         
        Jim (Just a guy who likes to build stuff)
      • Jerry Durand
        ... I ve seen products where the anti-backlash nut is just two nuts with a spring between them. You can also DIY nuts from acetal, someone had an instructional
        Message 3 of 14 , Mar 2, 2013
          On 03/02/2013 01:29 PM, Jim S. wrote:
          Another poster's remarks about using two nuts per screw works. It is much cheaper than any of the preloaded nuts sold commercially. You mount them so they can be preloaded against each other to eliminate backlash.

          I've seen products where the anti-backlash nut is just two nuts with a spring between them.

          You can also DIY nuts from acetal, someone had an instructional on doing this.
          -- 
          Jerry Durand, Durand Interstellar, Inc.  www.interstellar.com
          tel: +1 408 356-3886, USA toll free: 1 866 356-3886
          Skype:  jerrydurand 
          
        • jdkmlw
          Since I mentioned it earlier and others have commented about using two standard ball nuts instead of the more expensive anti-backlash ones, I d like to add
          Message 4 of 14 , Mar 2, 2013
            Since I mentioned it earlier and others have commented about using two standard ball nuts instead of the more expensive anti-backlash ones, I'd like to add this from what I have done and heard from others.
            Oh and you can just use one standard ball nut, but you will have a small amount of backlash and it will increase over time, so if you just want to get it up and running, one will work for starting out.


            Yes you can put spring pressure between them, this takes up the slack and keeps them close to zero backlash, and the spring pressure compensates for wear. But you need to use a strong spring or you can get bounce while cutting, so most normal coil springs won't work.
            I've seen a lot of people use Belleville Washers which are heat treated as spring steel, and can have a spring force from like 10-35 pounds per washer (in the sizes used for a 1/2" - 5/8" screw) and these washers can be stacked for more pressure.


            But what I did was made the mount that went to the table and one of the ball nuts was threaded into it and locked with three set screws to keep the ball nut body locked in the mount.
            Then I just made a simple aluminum square piece with a hole in the center that was threaded for a ball nut and drilled holes for set screws from the sides to lock that ball nut, and cut a groove on one side to make tabs or ears to fit over the body of the ball nut on the mount.
            I screwed the second ball nut into the square piece (smooth side) and started the ball screw in this one first, just enough for the ball screw to start out the other end of the ball nut, then holding this against the first ball nut (on the mount) so those tabs or ears were on both sides of the ball nut body I finished turning the ball screw through both ball nuts.
            Now to take out the backlash I held the square piece of aluminum and unscrewed the second ball nut (away from the first) until there was tension but the ball screw still turned smoothly, think it was about 1/16 or 1/8 of a turn, then locked it in place with the set screws.

            The way I did it will most likely get backlash over time, but for it being a hobby machine I think it will take a long time for this to happen, and I plan to redo it later (or buy a newer machine) once I get the hang of the programs.
            Hope this rambling helps someone :)


            --- In mill_drill@yahoogroups.com, Jerry Durand <jdurand@...> wrote:
            >
            > On 03/02/2013 01:29 PM, Jim S. wrote:
            > > Another poster's remarks about using two nuts per screw works. It is
            > > much cheaper than any of the preloaded nuts sold commercially. You
            > > mount them so they can be preloaded against each other to eliminate
            > > backlash.
            >
            > I've seen products where the anti-backlash nut is just two nuts with a
            > spring between them.
            >
            > You can also DIY nuts from acetal, someone had an instructional on doing
            > this.
            >
            > --
            > Jerry Durand, Durand Interstellar, Inc. www.interstellar.com
            > tel: +1 408 356-3886, USA toll free: 1 866 356-3886
            > Skype: jerrydurand
            >
          • jdkmlw
            Since I mentioned it earlier and others have commented about using two standard ball nuts instead of the more expensive anti-backlash ones, I d like to add
            Message 5 of 14 , Mar 2, 2013
              Since I mentioned it earlier and others have commented about using two standard ball nuts instead of the more expensive anti-backlash ones, I'd like to add this from what I have done and heard from others.
              Oh and you can just use one standard ball nut, but you will have a small amount of backlash and it will increase over time, so if you just want to get it up and running, one will work for starting out.


              Yes you can put spring pressure between them, this takes up the slack and keeps them close to zero backlash, and the spring pressure compensates for wear. But you need to use a strong spring or you can get bounce while cutting, so most normal coil springs won't work.
              I've seen a lot of people use Belleville Washers which are heat treated as spring steel, and can have a spring force from like 10-35 pounds per washer (in the sizes used for a 1/2" - 5/8" screw) and these washers can be stacked for more pressure.


              But what I did was made the mount that went to the table and one of the ball nuts was threaded into it and locked with three set screws to keep the ball nut body locked in the mount.
              Then I just made a simple aluminum square piece with a hole in the center that was threaded for a ball nut and drilled holes for set screws from the sides to lock that ball nut, and cut a groove on one side to make tabs or ears to fit over the body of the ball nut on the mount.
              I screwed the second ball nut into the square piece (smooth side) and started the ball screw in this one first, just enough for the ball screw to start out the other end of the ball nut, then holding this against the first ball nut (on the mount) so those tabs or ears were on both sides of the ball nut body I finished turning the ball screw through both ball nuts.
              Now to take out the backlash I held the square piece of aluminum and unscrewed the second ball nut (away from the first) until there was tension but the ball screw still turned smoothly, think it was about 1/16 or 1/8 of a turn, then locked it in place with the set screws.

              The way I did it will most likely get backlash over time, but for it being a hobby machine I think it will take a long time for this to happen, and I plan to redo it later (or buy a newer machine) once I get the hang of the programs.
              Hope this rambling helps someone :)


              --- In mill_drill@yahoogroups.com, Jerry Durand <jdurand@...> wrote:
              >
              > On 03/02/2013 01:29 PM, Jim S. wrote:
              > > Another poster's remarks about using two nuts per screw works. It is
              > > much cheaper than any of the preloaded nuts sold commercially. You
              > > mount them so they can be preloaded against each other to eliminate
              > > backlash.
              >
              > I've seen products where the anti-backlash nut is just two nuts with a
              > spring between them.
              >
              > You can also DIY nuts from acetal, someone had an instructional on doing
              > this.
              >
              > --
              > Jerry Durand, Durand Interstellar, Inc. www.interstellar.com
              > tel: +1 408 356-3886, USA toll free: 1 866 356-3886
              > Skype: jerrydurand
              >
            • jdkmlw
              Sorry for the double post
              Message 6 of 14 , Mar 2, 2013
                Sorry for the double post
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