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  1. #1
    I'm looking for a source for a low-backlash ball screw for the quill of my Fehlmann mill-drill (see my previous thread on this machine).

    The machine was previously set up with a very nicely constructed worm and wheel drive to the quill rack and pinion, but backlash in the worm and wheel (not the rack and pinion) has led me to consider using a ball screw instead. The photo shows an old actuator ball screw that I've set up to prove the principle.
    Click image for larger version. 

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    While positional accuracy over the 120mm of travel is not important backlash is. A dual nut would make sense and would probably be OK since I can accomodate a maximum thread length of 250mm. I've looked through eBay and am unable to find double-nut screws and am unable to seperate the wheat from the chaff in respect of other screws. Some guidance would be appreciated.

    David

  2. #2
    In terms of ebay I found this seller to be about the best when it comes to C7 double nut (DFU) screws. Bought around a year ago for conversion of an AMAT25LV benchtop mill.
    I got my screws down to around 0.015mm backlash using some thin tin foil (approx 0.05mm thickness in total) to pack between the slave nut and spacer.

    Or you could spend fortunes on C5 or lower using DFU nut in your searches.

  3. #3
    Quote Originally Posted by dazp1976 View Post
    In terms of ebay I found this seller to be about the best when it comes to C7 double nut (DFU) screws. Bought around a year ago for conversion of an AMAT25LV benchtop mill.
    I got my screws down to around 0.015mm backlash using some thin tin foil (approx 0.05mm thickness in total) to pack between the slave nut and spacer.

    Or you could spend fortunes on C5 or lower using DFU nut in your searches.

    Thanks for your reply. Did you mean to put a link to the seller in your post? I'd be pleased to take a look at their stock.

    Best regards

    David

  4. #4
    Quote Originally Posted by Agathon View Post
    Thanks for your reply. Did you mean to put a link to the seller in your post? I'd be pleased to take a look at their stock.

    Best regards

    David
    Oooops. Sorry.
    This one:
    https://www.ebay.co.uk/str/cyber-ebu...at=22348999012
    These are the ones on my machine:
    https://www.ebay.co.uk/itm/2-set-DFU...72.m2749.l2649

    Don't use thrust bearings with the Chinese screws. More hassle than it's worth. Design the machine to fit angular contact bearings, I've used some Dunlop on my AMAT25 which were relatively cheap and some unbranded which seem fine too.

    I had thrust bearings on my Sieg X2 and it wasn't very good. They cause your screw to run bendy as they don't seat on the ends well.
    Last edited by dazp1976; 1 Week Ago at 12:42 PM.

  5. #5
    Quote Originally Posted by dazp1976 View Post
    Many thanks.

  6. #6
    Quote Originally Posted by Agathon View Post
    Many thanks.
    The picture shows them with no spacers but all mine came properly done.
    I ordered spare sets for the AMAT and some for rebuilding my Sieg.

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