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  1. #16
    Join Date
    Jun 2016
    Location
    Sydney
    Posts
    283

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    are most modern lathes built with these types of screws instead of backlashy ones ?
    Modern commercial production-type machines - yes. Cheap little Chinese home lathes, no. The ball screws are more expensive.

    I have to agree that the acetal nut idea might be the best for you at this stage. Done exactly as described the nut can be a bit tight, but acetal is cheap enough that you can afford to experiment.

    Cheers
    Roger

  2. #17
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

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    By all means replace the nut, but don't expect it to eliminate the problem. I replaced my cross-slide nut and while it reduced the backlash, there's still quite a bit there. I need to reface the collar as described in the doc I posted above and also in the Hercus Textbook of Turning.
    Chris

  3. #18
    Join Date
    Oct 2004
    Location
    Southern Highlands NSW
    Posts
    1,894

    Default

    Both the nut and screw wear.
    Replacing nut only might reduce backlash, but wear on the screw is uneven so there will still be some play somewhere.
    Uneven screw wear could translate to inconsistent movement of the slide with respect to dial measurement, but it has to be pretty bad to matter I think.
    Installing a digital readout (DRO) overcomes screw wear, because it measures actual linear movement, unlike the dial.
    Have you leveled your lathe? That could help accuracy, you need an accurate level tool.

  4. #19
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    3,228

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    Inspired by this thread, I finally decided to remove the slop from the graduated collar on my 260. The setup is shown. Not shown in the pic is the compound rotated to 90 degrees to take the place of the cross-slide which is obviously out of action during the operation. Prior to this procedure I was just able to slip a 0.15mm feeler into the gap between the graduated collar and the fixed collar. You could see movement between the two when pushing and pulling on the compound. After the operation there is no visible movement between the two parts. However there is still quite a bit of backlash in the nut/screw interface. At a guess I'd say I have removed 10-20% of the backlash. I reckon it's a worthwhile fix. Took about 30 minutes. I used two Tally Ho cigarette papers for the shim.

    Watch out for the tiny woodruff key and the brass pad that goes under the locking screw when disassembling.

    Sorry about the PDFs. My iPhone has started taking photos in a new format (HEIC) after a recent iOS upgrade. The forum doesn't recognise HEIC and I couldn't work out how to convert to HEIC to JPEG, so PDF it is.
    Attached Files Attached Files
    Chris

  5. #20
    Join Date
    Sep 2018
    Location
    South Australia
    Posts
    88

    Default

    Sincere thanks to everyone for the comments, advice and effort.

    Nadroj, no, as yet I have not levelled the lathe. It is in my garage at the moment; it ultimately must move to my shed, so I will fit up the VFD while in the garage then break it all down, move to the shed, set up and level.

    Regarding the backlash, I think the plan will be to live with the lathe for awhile, then try replacing the nut and screw with new parts, then if still not happy try the skimming trick and maybe even a custom acetal nut. I love doing this sort of stuff so happy to try a few things.

    Again, thanks guys.


    Moz

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