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Grizzly G0776 - 13" x 40

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  • Grizzly G0776 - 13" x 40

    My lathe is about 3 months old and the cross slide will not ajust. I have work on the gibs ajusted them and the cross side nut like they say in the manual. So when I dial it in one 360 deg., it is fine for about 3 turnes no backlash one more turn and it is back. I also have cranked it all the way back and start to move it in to make a cut and 4 or 5 turns it is there this sucks. It like the cross side nut is no good .

    Al so do some of you guys lape the cross side in I have seen that done on mine lathes I was just woundering, and does it work

    And Saturday, November 11
    Veterans Day 2017 in United States of America so go get youe free stuff iam after the krispy kreme soooo good, ! and a coffee and then to denny's

    go here for the free stuff https://militarybenefits.info/vetera...ls-free-meals/ Make the gov feed us, I look forward to this and my sweet angle goes with me

  • #2
    Virtually all leadscrews have some amount of backlash. Even if they don't start out that way, they will wear with use and get looser in the most used area.


    The common way to overcome the problem is to always back out more than you need, and then move it in before turning. If you overshoot, back up more than the backlash and then move in again.


    Dan
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

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    • #3
      Sounds like the nut to me too. Pull it out and look at it and the lead screw. Something is broke!

      Thanks for your service too.

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      • #4
        Originally posted by Brett Hurt View Post
        My lathe is about 3 months old and the cross slide will not ajust.
        What are the symptoms that you are trying to solve by adjusting the gibbs?

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        • #5
          There is a screw at each end of the gib. You have to adjust both of them to work together. If you leave one loose, it allows the gib to go in too far and bind up. This may or may not be one of the problems, some things are kind of hard to diagnose long distance.
          Kansas City area

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          • #6
            What are you calling "backlash"?

            The gibs do not adjust backlash, they adjust the fit of the slide to the ways. If the slide jammed up, or was sloppy loose, the gibs can help.

            If you have backlash, meaning that the feed handle turns some amount without moving the slide, check to see that the feedscrew nut that the screw goes through is tightened down and is not loose on its mounting. Also check to see that the screw does not move lengthwise.

            If the nut is loose, then the first thing the screw does is move the nut, then after the nut has moved as far as it can, the slide moves. Same with the screw. if it can move relative to the slide, then it will move until it comes up against its bearing on the slide and starts to push the slide.
            Last edited by J Tiers; 11-11-2017, 10:28 AM.
            2730

            Keep eye on ball.
            Hashim Khan


            It's just a box of rain, I don't know who put it there.

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            • #7
              Assuming the 13x40 design is similar to the 12x36, there is a split acme nut for the cross slide. The adjustment screw forces the split nut further apart, reducing backlash. However, zero backlash is not a realistic goal.

              In addition to the acme nut, backlash may be caused by slop in the thrust bearing. The bearing preload can be adjusted -- and you might want to grease the bearing while you are at it because it may or may not have been greased at the factory. Adjusting the bearing preload on the cross slide is usually the single biggest improvement on Chinese lathes.

              As the others have said, gib adjustment is a separate issue.
              Last edited by MTNGUN; 11-11-2017, 07:12 PM.

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              • #8
                If it's that new then it's quite possible that you've still got some burrs or other on the lead screw or there may even be some crud in the nut halves. Have you taken the whole thing apart and cleaned it?

                I would not want to use lapping compound on the nut and screw. The grit will become embedded in the brass of the nut parts and be extremely difficult to be sure you get it all cleaned out. That's the way that lapping works. A softer material accepts the particles being pressed into the surface and then it cuts the harder material. It's really tough to get all that abrasive out of the surface of the softer metal afterwards. And so it ends up wearing the lead screw forever.

                In the end I'd also agree that it's going to be impossible to achieve a truly zero backlash in the lead screw dial. My own Taiwanese lathe has .004 to .005 backlash between points where it moves from pushing forward to starting to come back. That turned out to be the least amount I could set it for that did not result in some binding. Although that was a quite a number of years ago. So perhaps it was more like .002 to .003 back then and it's opened up by the extra thou or two.
                Chilliwack BC, Canada

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                • #9
                  I think what I'm hearing is:
                  Adjust the gib for a good fit at some position, crank the cross slide three or four turns in and the gib is not adjusted right.

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                  • #10
                    Ok I got down to about .003 of back lash but there is a soft spot in it. then it gets lossss, I have messed with it all weekend but did get my krispy kreme and it was good. I will call grizzly this week for a new nut and scew for it is still under woranty. I only have about 10 hours on it at frist it was giveing a good finish. and hitting size I have mostly cut 6061 alu. on it and some steel.

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                    • #11
                      Originally posted by Brett Hurt View Post
                      Ok I got down to about .003 of back lash but there is a soft spot in it.
                      You do realize that your lathe is supposed to have backlash? That is part of the art and skill of working a lathe is making it so it doesn't matter.

                      Anything under 0.010" of backlash on a lathe is good.

                      Tightening up on the split-nut too much to remove backlash (which will probably never be below 0.003" on an acme lead screw) promotes excessive wear of the lead screw.
                      Last edited by tmarks11; 11-12-2017, 10:27 PM.

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                      • #12
                        Agree.

                        If I had 0.003" backlash on ANYTHING, I'd be happy as a clam in mud. Instead, I have 0.025" on some. They work fine.

                        Now, being that yours is new, I'd expect that low a reading. What do you mean by a soft spot?
                        2730

                        Keep eye on ball.
                        Hashim Khan


                        It's just a box of rain, I don't know who put it there.

                        Comment


                        • #13
                          Originally posted by Brett Hurt View Post
                          Ok I got down to about .003 of back lash ... I will call grizzly this week for a new nut and scew.
                          0.003" is reasonable.

                          Did you adjust the preload on the thrust bearing (inside the handle-collar thingy)?

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                          • #14
                            If you are concerned about backlash, just install a two-axis DRO and be done with it. That way, assuming good accuracy in the scales, you are reading the absolute movement of the cutting tool. It worked for me.

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                            • #15
                              I did all that but hve not made a cut yet, the Air Compressor Pressure Switch went out and Iam all over this at the monent, have you guys used any of those from ebay that are lets say cheapppp!!. about under $20 looks like I have to rebuild it or look at every thing 30 years on a campbell hausfeld air compressor not bad I did change the oil every year stuff last any insight on pressre switchs

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