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26th May 2021, 06:42 AM #1Novice
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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.
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26th May 2021, 09:40 AM #2Most Valued Member
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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.
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26th May 2021, 09:44 AM #3
G day Blackpig
Welcome to the MetalWork Forums.
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Again, welcome to our forums.
Grahame
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26th May 2021, 04:57 PM #4
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.
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26th May 2021, 07:15 PM #5Most Valued Member
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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.
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26th May 2021, 10:46 PM #6
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.
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27th May 2021, 08:32 PM #7Most Valued Member
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- Apr 2012
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- Healesville
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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.
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24th Sep 2021, 05:56 AM #8Novice
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- May 2021
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- Surrey
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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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