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  1. #1
    Join Date
    Oct 2007
    Posts
    398

    G0602 X-Axis Ball Screw

    Hi all,

    I converted a Grizzly 10X22 lathe to CNC last year. I was in a hurry, though and took some short cuts. The one glaring issue I want to correct is that I initially mounted the X-Axis ball screw on top of the cross slide instead of under the saddle where the original lead screw was located. My problem then as now is the ball nut has a flange that's too big to fit in the channel.





    These are super cheap ball screws I got off ebay from linearmotionbearings. They have so far been both accurate and durable. My only complaint is he only has flanged ball nuts available. What I'm considering is cutting the channel in the saddle to fit the ball nut, but I'm worried that will weaken the dovetails too much. Has anyone tried this?

    Thanks,

    Jeff

  2. #2
    Join Date
    Feb 2006
    Posts
    7063
    If you really want to keep that screw and nut, why not re-machine the nut to remove the flange, and put a different end on it?

    Or, machine a couple of "notches" in the saddle and use set-screws to attach the nut, and let the screw travel back and forth with the cross-slide?

    Regards,
    Ray L.

  3. #3
    Join Date
    Aug 2004
    Posts
    2849
    I believe the ballnut is attached to the cross-slide and you want it to travel down the channel of the saddle?

    If so then as Ray said "machine the flanges of the ballnut to allow it to travel through the channel". Then you will need to machine a bracket to allow you to attach the ballnut to the cross-slide.

    Paul

  4. #4
    Join Date
    Oct 2007
    Posts
    398
    Yes, the ballnut is attached to the cross-slide. I was hoping to avoid machining the ballnut, though. It has proven to be much harder than the ballscrews were. I will have to grind it, and probably get some grit inside the nut.

    You two are probably right, though. Machining the ballnut is the better option. It's just that cutting the saddle would be so much easier...

    Jeff

  5. #5
    Join Date
    Aug 2009
    Posts
    986
    Quote Originally Posted by Flenser View Post
    I will have to grind it, and probably get some grit inside the nut.
    I wouldn't consider grinding a ballnut without first unloading it. After all, you'll be getting metal dust everywhere, and also dipping the ballnut into water to cool it as you grind. Getting grit inside is not likely, it's certain.

    But if you've unloaded it, then it's no problem. Just clean up the nut with a parts washer or brake cleaner once you're done, and put it back together.

  6. #6
    Join Date
    Oct 2007
    Posts
    398
    I was lead to believe reassembling a ball nut can be very... challenging. I've never tried it, though.

  7. #7
    Join Date
    Feb 2006
    Posts
    7063
    Quote Originally Posted by Flenser View Post
    I was lead to believe reassembling a ball nut can be very... challenging. I've never tried it, though.
    It's really not a big deal at all, once you know how.

    Regards,
    Ray L.

  8. #8
    Join Date
    Oct 2007
    Posts
    398
    Well, getting it on and off the screw without losing the bearings was pretty simple, but I haven't been able to find much information on reinserting the bearings once they are free of the housing.

    I have a "spare" empty housing now, because I was playing with g-code commands right after getting everything hooked up - everything but the limit switches, that is. The bearings were scattered, but the ones I found could be inserted by unscrewing the nut just enough to leave a bearing sized gap. Is that essentially what I would need to do??

    Thanks,

    Jeff

  9. #9
    Join Date
    Feb 2006
    Posts
    7063
    Quote Originally Posted by Flenser View Post
    Well, getting it on and off the screw without losing the bearings was pretty simple, but I haven't been able to find much information on reinserting the bearings once they are free of the housing.

    I have a "spare" empty housing now, because I was playing with g-code commands right after getting everything hooked up - everything but the limit switches, that is. The bearings were scattered, but the ones I found could be inserted by unscrewing the nut just enough to leave a bearing sized gap. Is that essentially what I would need to do??

    Thanks,

    Jeff
    There is generally a removable ball return guide, that allows the balls to be slipped back in, with the nut on the screw, then the return guide is replaced.

    Regards,
    Ray L.

  10. #10
    Join Date
    Oct 2007
    Posts
    398
    Hm, there are only plastic inserts with no obvious way to remove them from the outside. If there is a return guide, I sure don't see it. These are the same as the ones I have. Maybe they are cheaper than I thought...

    Jeff

  11. #11
    Join Date
    Feb 2006
    Posts
    7063
    Quote Originally Posted by Flenser View Post
    Hm, there are only plastic inserts with no obvious way to remove them from the outside. If there is a return guide, I sure don't see it. These are the same as the ones I have. Maybe they are cheaper than I thought...

    Jeff
    I have not taken apart that style, but those plastic plugs must be the returns. I would guess they just pry out, to expose the ball tracks.

    Regards,
    Ray L.

  12. #12
    Join Date
    Oct 2007
    Posts
    398
    I found a thread with a few different people reassembling these specific ballnuts. It's probably not quite as simple as machining the saddle, but maybe not beyond my limited skills

    I also cut one flange from the spare housing using a diamond dremel wheel mounted in the the mill. With max speed of 1500 RPM I was only able to cut 0.003" at a time without the wheel chattering, but at that depth I could feed as fast as I could turn the handle. I was surprised it cut so well after having dulled a HSS end mill and chipped a carbide insert with little more than a few scratches to show for my effort.

    Thanks everyone for the help. The g0602's saddle thanks you as well!

    Jeff

  13. #13
    Join Date
    Oct 2005
    Posts
    1237
    I hate thinking I'm missing the forest for the trees, but why does the ball nut have to go all the way through? Why can't the ball? screw float? Two notches with a cover plate clamping the ball nut home would work. Then the ball screw floats and you change where and how you mount your drive motor. I need another few pictures to see how it all fits, but a trapped nut seems like a good fit for that style of ball nut.

  14. #14
    I might consider rotating the nut 90 degrees and only need to remove one side of the nut.
    use the other sides 2 holes to mount to the cross slide.
    looks like the saddle could go untouched then.
    Hoss
    Attached Thumbnails Attached Thumbnails bn01edit.jpg  
    http://www.hossmachine.info - Gosh, you've... really got some nice toys here. - Roy Batty -- http://www.g0704.com - http://www.bf20.com - http://www.g0602.com

  15. #15
    Join Date
    Oct 2007
    Posts
    398
    Quote Originally Posted by MrWild View Post
    I hate thinking I'm missing the forest for the trees, but why does the ball nut have to go all the way through? Why can't the ball? screw float? Two notches with a cover plate clamping the ball nut home would work. Then the ball screw floats and you change where and how you mount your drive motor. I need another few pictures to see how it all fits, but a trapped nut seems like a good fit for that style of ball nut.
    Not sure I understand. Do you mean let the screw move with the cross slide? Without the nut moving along the channel, that's the only setup I can picture. It would requre different bearings and motor mount at least, and I wouldn't be able to use direct drive as I am now.

  16. #16
    Join Date
    Oct 2007
    Posts
    398
    Quote Originally Posted by hoss2006 View Post
    I might consider rotating the nut 90 degrees and only need to remove one side of the nut.
    use the other sides 2 holes to mount to the cross slide.
    looks like the saddle could go untouched then.
    Hoss
    That might work if the screw is long enough. I may have cut it a little short to mount the nut much further than the center of the slide.

  17. #17
    Join Date
    Oct 2007
    Posts
    398
    Just an update. The ballnut is machined and reassembled. There was a trick to getting the balls reloaded that took me a while to figure out, but after that it went pretty smoothly. I also learned the plastic plugs are labeled differently for a reason. One has a 5 and the other a 7 stamped on it. I dunno the meaning of the numbers, but if you swap them (as I did the first time) the turn around points in the wrong direction.

    Even after removing the flange I had to trim a tenth off each side of the cross slide channel. I'm planning to make the mount a press fit, maybe adding a set screw against the square section to prevent it from slipping. I ordered a drill bit that gets me close to the right dimensions. I'm making the mount from steel and don't want to spend an hour with a boring bar widening a hole in steel. I spent almost that much time just grinding the ballnut flange :tired: I was pretty happy with how it came out, though.

    Jeff



  18. #18
    Join Date
    Feb 2009
    Posts
    137
    Jeff,
    Looks like the mode is comming along well. I also have a 10x22 and I am thinking to convert it but I have to get the VFD done first.

    How are the quality of those ball screws?

    Did you turn the ends on the lathe?

    Matt

  19. #19
    Join Date
    Oct 2007
    Posts
    398
    Matt, I don't have a lot of experience with other ballscrews to compare these to, but I have been impressed with them. I will probably use them for my mill conversion as well. I did turn them on the lathe. Hoss has a video of theprocess, and I did essentially the same thing. Though unlike Hoss, who knows what he's doing, I had to ruin a few tool inserts first. I also ground the last .05 or so with a Dremel strapped to the tool changer to get a smooth finish.

    Jeff

  20. #20
    Join Date
    Oct 2007
    Posts
    398
    As requested, I'm posting some pics of the conversion I did several years ago. There's a lot I would do differently today, and probably I will at some point. I think it might be useful, though, to show some of the mistakes I made.

    Here's the whole machine. The "enclosure" is mostly to keep chips out of my hair when the spindle is spinning at high speed. I have another Lexan sheet that covers the opening when metal starts flying.

    Click image for larger version. 

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    I removed the compound travel assembly and added a block to mount the QC tool post on. I made two serious mistakes here. The first was mounting the x-screw above the cross slide. The first part of this thread dealt with me correcting that error, but you can still see the slot in the mounting block where it used to sit. The second error was using that angle bracket as a mount. There's enough leverage at the tool to flex that bracket 0.02" or more on heavy cuts. I really need to fix that... someday.

    Click image for larger version. 

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    Note the limit switch in the above pic to the right of the motor mount. This is the other one on the back side of the cross slide. Too bad I didn't mount it until AFTER I spun a ballnut right off the end of the screw : ) The front switch was once tripped by chips during a run. I told myself I would do something about that, but never have.

    Click image for larger version. 

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    Here's the z screw beeaing and motor mounts. The angle brackets aren't much of a problem here. They don't flex like the x screw mount does, for some reason. Still, if I ever rework it, I'll move the screw closer to the lathe bed. It is always getting fouled with chips and cutting oil when I cut steel. It also made mounting the other bearing difficult. I had to shave off part of the block so it would slide behind the ballnut mount on the carriage.

    Click image for larger version. 

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    I removed the gearbox when I removed the lead screw. The mounting holes were convenient for mounting the left z-screw bearing. The e-stop switch has both the spindle motor enable-relay and the e-stop on the G540 wired to it.

    Click image for larger version. 

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    Finally, here's the encoder pickup. I forget the part number of that component, but it's electrically equivalent to the setup CNC4PC sells. I stumbled on a bag of 20 of the things selling on ebay for $4 after I dropped a live center on the one from CNC4PC. Now at least I have spares : ) I wasn't thinking when I took the pic, so you can't see the notch in the disc, but it's about 2 inches long to make sure Mach can pick up the signal at high spindle rates.

    Click image for larger version. 

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