Lathe Headstock Bearing Replacement Recommendations?

Discussion in 'Machine Modifications' started by cfellows, Oct 27, 2011.

  1. Oct 27, 2011 #1

    cfellows

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  2. Oct 27, 2011 #2

    MachineTom

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    Are they regular BB?, sounds odd for a lathe spindle, Doesn't everyone use angular contact bearing for a spindle application. Find the numbers on the bearing, and you will know the answer.

    Angular contact bearing, have balls and a cage like a regular ball bearing. But the grooves iin the outer race cover about 100° of the ball radius, and the inner race also about 100°, where with regular ball bearings the ball contact area is around 20%. The bearings are select fitted by ball, and race, to millionths inch. A * will mark the high side of the assembled bearing, and if the machine takes 4 bearings at a single point, they are sold as a matched set.

    A set of roler bearings, set up perfect, will be out of adjustment as soon as the spindle warms up, now you have a loose spindle with a heavy chuck on the end, going wherever it wants.

    not an idea for good machining results.
     
  3. Oct 27, 2011 #3

    cfellows

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    Near as I can tell, the current bearings are not angular contact. There is one bearing with a snap ring on the front and one bearing on the rear of the headstock. Two Belleville washers apply pressure against the back of the rear bearing and pulling the spindle back against the face of the front bearing. I have found angular contact bearings the right size on Ebay, but they cost from $175 to over $300 apiece. Don't know if I really need that kind of precision...

    With the tapered roller bearings, I would continue to use the ball bearing on the rear of the headstock and the belleville washers to apply a constant pull against the font, taper roller bearing. This should keep everything tight with temperature variations.

    I've attached a drawing of the current headstock assembly

    Chuck

    Lathe Spindle.png
     
  4. Oct 27, 2011 #4

    ShedBoy

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    What about lubrication? These tapered bearings are not shielded.
    Brock
     
  5. Oct 27, 2011 #5

    dalem9

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    Why can't you use tapered roller bearing. Or are they not heavy enough.Dale
     
  6. Oct 28, 2011 #6

    cfellows

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    That's what I'm asking... is there any reason I couldn't use tapered roller bearings to replace the existing, deep groove ball bearings?

    I'm assuming I could just pack the bearings in grease. There is a shield on the spindle which shields the ball bearings.

    Thx... Chuck
     
  7. Oct 28, 2011 #7

    dalem9

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    Chuch My mill and my lathe both have tappered roller bearings in them .Dale
     
  8. Oct 28, 2011 #8

    steamer

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    Chuck,

    Lots of lathes ....like Harrison and American Pacesetter use taper roller bearings.....Horses for courses.

    I would be somewhat suprised if your bearings were not angular contact....but ...deep groove radials do fine for relatively light axial loading...provided they are preloaded ...and with the belevilles....they are.

    Now

    Why change them?.....the bearings that are in there lasted at least 30 years....at least since the last Logan left the factory anyway....I would say new ones would last a long time.

    Regular deep groove conrads will perform better at say 3000 rpm than taper roller grease packs.....nice thing about the conrads is that you could probably get them sealed if your installation allows it and they are real cheap compared to angular contact.


    Just my thoughts.....

    Dave
     
  9. Oct 28, 2011 #9

    cfellows

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    I have another lathe headstock for the logan that lets me mount the motor underneath the lathe instead of behind it. Problem is, the replacement headstock bearings feel kind of rough. Could just need cleaning, but I thought I would explore replacing them with tapered roller bearings. Would love to have angular contact bearings, but they are just too expensive.

    Part number on the existing front bearing is Fafnir 9110KDDG. These are simply described as deep groove. By the way, the tapered roller bearings on Ebay are about the same price as replacement deep groove bearings, also on Ebay. The only problem is that the tapered roller bearings don't have a snap ring like the replacement deep groove bearings so I'd have to fabricate something.

    Chuck
     
  10. Oct 28, 2011 #10

    Ken I

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    Chuck, Angular contacts are better at handling axial load (thrust against the spindle resulting from feed) than concentric radials (which handle radial thrust better) - but in both cases can be had in metal shielded (ZZ) or rubber sealed (RS) - "sealed for life" already pre-greased.

    My choice would be the angular contacts - especially since you have constant running pre-load from the Belville washers

    Taper rollers are all good and well but lubrication may prove to be problematical (no seals).
    Tapered rollers are highly intollerant of alignment problems (unlikely in your application).

    2c Ken
     
  11. Oct 28, 2011 #11

    Niels Abildgaard

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    My Boxford is open to challenge by all Southbends and has two Timkem tapered rollerbearings.
    Shielded with an air gap of 0.1 mm and gets some fresh grease on X-mas.


    IMG_0396.JPG
     
  12. Oct 28, 2011 #12

    Stan

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  13. Oct 28, 2011 #13

    MachineTom

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    With the Belleville washers, think about this, the tapered roller bearing, when side loaded, as when cutting, would naturally try to deflect, and climb a bit out of the outer race, this force will be countered by the rear bearing, but the spring washer will have to allow some movement in an axial direction, and that compression of the washers, however slight, will show up in the finish of the workpiece. If the compressive preload force of the washers was to exceed the axial forces of cutting action, then there may not be a problem. But it would be a fair amount of work to find out.

    To groove the bearing cup EDM would be first choice, but at a $$$cost. buy a carbide grooving tool that is about half or a little more that the groove needed, about 250 sfm and plenty of lube, may need earphones for the squeal.
     
  14. Oct 30, 2011 #14

    velocette

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    Hi Chuck
    I find this interesting topic with all the varied views on how to do this job. It all come down to personal preferences based on Experience and access to the right information. Taper roller bearings will carry the greatest loading and is a preferred option.

    This can be achieved if you machine a "Circlip Groove in the headstock bearing housing to support the "Outer Race".

    Being familiar with "Logan Lathes" by there reputation only. I will not attempt to make a call as to why they have ball bearings in the headstock.
    Take this a observation only

    The bloke that designed it got it accepted by his peers and has served very well on this and many more machines World Wide
    this is a fine machine and will still be capable of doing a good job for many years to come.

    Enjoy it Chuck




    I
     
  15. Apr 12, 2012 #15

    n4zou

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    Considering that your lathe is not in a production environment the replacement bearings will out live your use of the lathe. Now consider the person that will inherit it or perhaps purchase it from your estate after you are gone. If you change the original design you will devalue it considerably, even if that upgrade enhanced it's performance.

    You did not post the width of your 50 X 80 bearings so I am going to assume they are 16 wide which is the most common width for this size bearing. Personally I would purchase the same size bearings and leave it in a stock condition. A quick check of Amazon.com reveals a better replacement bearing due to it's maintenance free sealed design and they only cost $9.95 each.

    http://www.amazon.com/6010RS-Bearin...4?s=industrial&ie=UTF8&qid=1334234472&sr=1-14
     
  16. Apr 12, 2012 #16

    f350ca

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    I'd recommend staying with the original bearings. Tapered roller bearings are generally used in pairs with preload, a radial load outside the pair results in an axial load that is carried by the second bearing. The higher the contact angle in the bearing the greater the resulting axial load. In your case you'll be applying that axial load to the ball bearing. Ball bearings aren't great for that type of loading. When machining away from the headstock you'll be removing the preload on the tapered bearing as you compress the Belleville washers.
    It may work fine but may cause some unwanted results.
    Greg
     

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