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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > Taig Mills / Lathes > Anyone know how to preload the x,y screw?
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  1. #1
    Join Date
    Mar 2005
    Posts
    266

    Anyone know how to preload the x,y screw?

    I was experimenting with backlash compensation (IMO its awful I wont use it). I had .0035 on the X and .0012 on the Y as best I could tell anyway. The z had very little backlash but thats only because it has the heavy weight so that the backlash doesn't come into play as much.

    I have a few ideas in mind about using a double nut to remove backlash and compensate for wear automatically but its *much* more complicated than it sounds. Essentially the nuts that are there remain the same and can be used to remove most of the backlash like they do now. A second nut is added near the original nut and is mounted to its own slide with a spring pushing against it and the original nut for a "preload" of maybe 25-50 pounds.

    Might even be able to estimate wear and remaining life of the pre-loaded nuts by measuring the distance between them.

    I'll test my bobcad skills and get some kind of mockup to show what I mean but in the meantime I am interested in what others have done to minimize backlash.

  2. #2
    Join Date
    Jul 2009
    Posts
    205
    .0035 is waaaay to much for a taig. .0012 is reasonable, and you actually won't get all that much better than that most likely. if you consistently need less than .001 backlash, a stock taig just wasn't designed to do it.

    the split bronze nut (assuming you have a cnc-ready model with the split nut, and that it was made in the last 5 years or so therefore is bronze) is brutally easy to adjust, and should reduce backlash to around .001 or so.
    first make sure it isn't something else goofy like loose gibs or a loose nut on the end bearings causing the whole screw to move when force is applied. if everything is tight, adjust the split nut and you will be fine. nick carters site has instructions i believe. its actually very simple.

    in place of a/b nuts, you can also counterweight the axes instead. this has shown to work very well on several users machines in the past. simplest one i saw was to take a ball-bearing drawer slide screwed vertically on the back of the bench, and a 3/32" cable went from the back of the y axis to the rear of the bench, over a plastic roller, and down to a 5 pound weight on the drawer slide. this gave that much preload to the axis as it had to raise and lower the weight to travel, and like the z axis therefore had no backlash. this preload also added very little friction compared to what an a/b nut would. x axis did the same thing only with two rollers, one to change direction of the cable to the rear, and from there over and down the back with an identical slide and weight as the y axis. thats like $10 worth of components right there, easy to hook up and adjust without opening the machine or adding extra wear.

  3. #3
    Join Date
    Mar 2005
    Posts
    266
    This is kind of what I had in mind and using weights sounds easy. The split nuts on my machine look like brass to me but maybe not.
    Attached Thumbnails Attached Thumbnails AntiLash.jpg  

  4. #4
    Join Date
    Jul 2009
    Posts
    205
    i am assuming the mount is just to keep the second nut from rotating, while the spring allows it movement to maintain tension? that is actually kind of a neat setup.
    just remember that an a/b setup with metal nuts adds a lot of friction. also, it only works when the amount of force applied to the table is less than the spring applies. you put heavy loads or vibration to the table and it can overcome spring force. not major issues if you expect them, but you do trade a lot of speed and acceleration ramp for the lack of backlash.

  5. #5
    Join Date
    Jul 2011
    Posts
    0
    3 step:
    1: find the screw.
    2, preload the screw
    3, Install the parts as before....

  6. #6
    Join Date
    Feb 2008
    Posts
    194
    Quote Originally Posted by cameraguy View Post
    the split bronze nut (assuming you have a cnc-ready model with the split nut, and that it was made in the last 5 years or so therefore is bronze)
    I have an older CNC-ready model (I think it is about 10 years old). It has the split nut, but it appears to be made of brass. Did they change materials? Are users getting improved performance with the new split nuts?

  7. #7
    Join Date
    Jul 2009
    Posts
    205
    i have no idea exactly what they were before, i just know taig has told me the nuts on at least some of the machines i purchased a number of years ago are different material from the ones on the new machines i have ordered. i don't think they are any different of actual design, just of material for wear purposes.

    the new ones are a straight swap anyway, so if the old ones ever do wear out just order a replacement. not that i recall that ever being a particular problem with the old ones though.

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