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  1. #1
    Join Date
    May 2021
    Location
    Surrey
    Posts
    14

    Default 1952 Swiss made milling machine bearing grinding

    I’m new to this, but I really value the community support. I recently acquired a small Shaeffner W12 mill, old and well used but the ways are still nice. I have never really aspired to a mill, as they are normally too expensive, but this one was free as the owner is sadly too infirm to use it. The table x screw seems to have about 0.5 mm backlash which seemed rather excessive so I set out to explore what needed to be done. The lead screw is carried in rather simple bearings at each end mounted in cylindrical threaded in 1 ½ 16 tpi carriers.
    the race ways are deeply pitted but no sign of damage to the balls. DD66E50A-3347-41A0-B7CA-EB188252DF5A.jpg
    my plan is to grind the ways true using a fine W series mounted point in my Potts tool post grinder. I now have the points, a struggle to find them with ¼” spindles which I need for the W8 collet church of the grinder.
    my first step is to practice on some scrap races to see how good a finish I get and generally see how it goes before hazarding the real parts.
    My questions are thus:

    Has any one done something like this before, how did it go?
    Am I being daft?
    Does any one know why a Swiss built mill should have so many imperial threads in it(the bearings have metric dimensions though);
    would I be better off redesigning the way the lead screw transmits its thrust to the table?
    Any advice would be most welcome.

  2. #2
    Join Date
    Jul 2016
    Location
    Melbourne
    Age
    35
    Posts
    1,522

    Default

    Although its something that probably should be fixed i dont know if it will fix your problem, as theoretically just tightening those nuts would take their portion of the backlash out.

    How much free movement is there between just the nut and screw?

    Delicate job but doable, replace the balls while you are at it, don't penny pinch when it comes to a job like that, not enough meat in the parts to grind them twice.

    Id also triple check there is enough travel in the nuts that you'll be able to close them up 9nce you grind that much out of them.

    Sent from my SM-G973F using Tapatalk

  3. #3
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    G day Blackpig

    Welcome to the MetalWork Forums.

    You have landed amongst a great bunch of blokes who have a great deal of knowledge and experience and are willing to share it with anyone who needs a hand.

    To gain the greatest benefit of the forum take the tour to see what we do.


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    Many pages also have a sticky at the top.If you post its always a good idea to check the sticky ,if there is one there.

    Please post your questions in the appropriate MetalWork forum.

    Again, welcome to our forums.

    Grahame

  4. #4
    Join Date
    Sep 2012
    Location
    York, North Yorkshire UK
    Posts
    6,436

    Default

    Quote Originally Posted by Blackpig View Post
    I’m new to this, but I really value the community support. I recently acquired a small Shaeffner W12 mill, old and well used but the ways are still nice. I have never really aspired to a mill, as they are normally too expensive, but this one was free as the owner is sadly too infirm to use it. The table x screw seems to have about 0.5 mm backlash which seemed rather excessive so I set out to explore what needed to be done. The lead screw is carried in rather simple bearings at each end mounted in cylindrical threaded in 1 ½ 16 tpi carriers.
    the race ways are deeply pitted but no sign of damage to the balls. DD66E50A-3347-41A0-B7CA-EB188252DF5A.jpg
    my plan is to grind the ways true using a fine W series mounted point in my Potts tool post grinder. I now have the points, a struggle to find them with ¼” spindles which I need for the W8 collet church of the grinder.
    my first step is to practice on some scrap races to see how good a finish I get and generally see how it goes before hazarding the real parts.
    My questions are thus:

    Has any one done something like this before, how did it go?
    Am I being daft?
    Does any one know why a Swiss built mill should have so many imperial threads in it(the bearings have metric dimensions though);
    would I be better off redesigning the way the lead screw transmits its thrust to the table?
    Any advice would be most welcome.
    You may be better off finding a suitable bearing race and replacing it. It looks like it is pressed onto the end of the shaft and located inside the cup. Grinding bearing raceways is not just a matter of using a fine stone ! The raceway surface is polished after grinding to very fine tolerances.

    It would be be easier to turn a suitable housing and possibly the shaft to suit a new ball race.
    Best Regards:
    Baron J.

  5. #5
    Join Date
    Jul 2016
    Location
    Melbourne
    Age
    35
    Posts
    1,522

    Default

    Its very un swiss to use much imperial stuff but maybe in order to get export share they did. My astoba UW1 is "imperial" but the leadscrews are all metric trapezoidal threadforms but cut at an imperial pitch. Super fun stuff.

    Sent from my SM-G973F using Tapatalk

  6. #6
    Join Date
    Dec 2013
    Age
    56
    Posts
    1,416

    Default

    If they are pressed in, I'm sure you could buy cheaply and machine the outside or bore the inside diameter of some races to fit, and while your there balls as well.
    If not slightly modify the housing to take a new bought one of similar size.

    Personally I wouldn't grind races, there usually hardened and or hard chromed and polished as said to micron finish and you may disrupt that leaving a softer metal which will wear quicker.

    Sent from my 5007U using Tapatalk
    Using Tapatalk

  7. #7
    Join Date
    Apr 2012
    Location
    Healesville
    Posts
    2,129

    Default

    Quote Originally Posted by Blackpig View Post
    The table x screw seems to have about 0.5 mm backlash which seemed rather excessive so I set out to explore what needed to be done.
    G/day Blackpig, just to give you a bit of an idea I have 3 oldish mills and the backlash on the x screws on them varries between
    a 1/4 to 1/2 a turn......
    a suggestion, take your bits and pieces to a bike shop and see if they have something that might work, eg cups, cones and bearings.

  8. #8
    Join Date
    May 2021
    Location
    Surrey
    Posts
    14

    Default Re grinding bearings on the 1952 mill

    Well, this is not exactly a rapid feedback, life gets in the way of fun some times. However i spent a while thinking about the sundry helpful comments. In the end pragmatism dominated and I ground the bearings as I outlined. I spent a while polishing the resultant race ways and found that by using ⅛” balls I wasn’t quite running on the original tracks either. Upshot, a fair bit of nail biting but a result that works well and I’m more than pleased. Thanks for the council.
    Next plan is to explore fitting a DRO to address the irritating imperial axis screws.

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