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  1. #1
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    Default Angular Contact Bearing Help

    Im in a bit of a pickle. New bearings arrived for the CVA today. But it looks like they wont suit without serious modification. This isnt going to make much sense without a drawing but i wont be able to get it done until tomorrow.

    All the (few) angular contact duplex pairs i have come into contact have had the same width inner and outer races, that is how my new Fafnir MM212WI are. But the original hoffman bearings have a significantly shorter outer race (1mm different). the back side of the inner and outer is flush (they are mounted back to back so all the faces that meet the spacers are flush) but the front face of each outer race is 1mm short)

    the inner spacers are exactly 0.001" different in height (inner is smaller)

    Initially i thought i could just make a custom outer spacer, but i cant, to fit what i have here i would have to alter the front spindle retainer plate, and possibly the headstock, or send the bearings out to have their outer races ground. has anyone seen this setup before?

    Does anyone on the forum have a really really good surface grinder setup, im not really sure factory accuracy would survive grinding without extreme care.

    Ill post more photos and detail tomorrow, and start calling around but i dont think im going to find any.

    Regards and thanks - Ralph

  2. #2
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    Default

    Hello Ralph,

    Are you sure that you have the right bearings, they are also listed as wide inner ring. That would make them the same as the Hoffman ones. Not having the Hoffman number I can't check sizes.
    Best Regards:
    Baron J.

  3. #3
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    Default

    Sorry BaronJ the Hoffman number is N4689A then furhr round the race is NM.

    Both my usually good older bearing places gave me these as the replacement. Ill do more digging today

  4. #4
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    Good morning Ralph,

    My contact at Hoffman Bearings, says that the bearings you have are not the correct ones, I would suggest that you return them.
    Hoffman are going to check their records and stock to see if they can help ! It may take a little time but I will come back to you with what ever information I get.
    Best Regards:
    Baron J.

  5. #5
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    Default

    Okay thanks so much Baron! Much appreciated.

    I have now dropped those off to have the front faces of the outer race ground down by a local precision spindle rebuilder but I don't think they will get to it until next week at any rate.

  6. #6
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    Default

    Sounds like specials, made specially for the lathe, a bit like Monarch put a special flanged angular contact bearing in the 10EE. I have an opposite problem that you have. I needed a special angular contact with a snap ring. When I picked up a NOS New Departure from the US, it has a wide inner ring. So I need someone to grind down the inner ring on both sides to the same dimension as the outer ring. It is not a precision bearing though.
    Gold, the colour of choice for the discerning person.

  7. #7
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    Default

    Quote Originally Posted by caskwarrior View Post
    Does anyone on the forum have a really really good surface grinder setup, im not really sure factory accuracy would survive grinding without extreme care.
    Ralph could you post pics of the brg shell that needs grinding, if you get stuck it is possible that it could be done on my rotary table grinder if the brg shell can be secured to the table.

    cheers, shed

  8. #8
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    Default

    20180729_161352.jpg

    Just the outer race needs to be ground, it's 110mm across. I have given H and W the go ahead so I probably won't use your precious time.

    The offer is seriously appreciated though.

    As usual everyone pulls through with help and advice.

    Regards Ralph

  9. #9
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    Good Morning Ralph,

    I've just heard back from Hoffman, there is no stock of these bearings available at the factory nor at any of the distributors that they supply !
    However they can manufacture a matched pair for you.

    quote"
    QB 31.01.18

    HB Equiv. (N4689 A NM Hoff) to manufacture
    1 pair £720.00 per pair Delivery: 8 to 10 weeks
    Hoffman Bearings manufacture, made in the UK.

    They are supposed to be sending me a copy of the manufacturing specifications.
    At this point I'm inclined to concur with your decision to have the ones you have ground.
    Best Regards:
    Baron J.

  10. #10
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    The manufacturing specs would be interesting to see. I am surprised how cheap they are for custom bearings.
    Gold, the colour of choice for the discerning person.

  11. #11
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    Thanks so much BaronJ that is indeed a pretty decent price for custom bearings, it ended up costing about $200 to have the existing set ground down.

    Does make me wonder what some other people on the net got when they bought replacement bearings.

    There is room in the headstock and retainer to fit normal 212 bearings in so maybe that is what they did in other years than 1963.

  12. #12
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    Hi Ralph,

    With respect to them sending me the bearing specifications, which I queried, they said that they would come with the supplied bearings and that quality control would provide actual measurement figures.

    So it looks like I'm not going to be able to get them ! When I asked I did hope to get some technical specs. Sorry
    Best Regards:
    Baron J.

  13. #13
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    They would probably supply the OD and ID measurements of each bearing down to the micron level. That seems to be standard for all precision bearings.
    Gold, the colour of choice for the discerning person.

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