Schaublin 70 plain bearing is pooched - ideas....or part it out?
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  1. #1
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    Default Schaublin 70 plain bearing is pooched - ideas....or part it out?

    I acquired another Schaublin 70 recently, this is the plain bearing spindle model with the double taper at the inboard bearing - i think its 45 and 3 degrees. Previous hack operated with oil and the bearing seems really pooched, the owner was the type who was barely qualified to operate a lawn mower, not a fine machine tool, sad. Anyway, lamenting aside, there's scoring and it seems when you move the bearing all the way on the shaft, its still sloppy on the shaft - ie. there doesn't look like enough material to grind/lap it back in. afaik these are hardened and lapped steel bearings on a hardened and lapped shaft.

    I'd be ok attempting to make a part with one taper, but getting two tapers and perfect mate via lapping is something I'm not sure how to do or even if i'm up to it. So making a replacement bearing seems iffy.

    i'll contact Schaublin, but expect its an exercise.....if they have the part it'll likely be more than the lathe is worth in good condition. If thought of hard chroming the shaft, but then I'm back to 'how to lap a double angle conical bearing and its mate perfectly?"

    The lathe is otherwise pretty good, so i'd like to save it over parting it out.

    Any great ideas on solving this problem? Anyone converted one of these to roller element bearings?

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    what year is the machine?

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    Quote Originally Posted by dian View Post
    what year is the machine?

    I'm not really sure, its a plain bearing with hardened steel bearings (like a watchmakers lathe). I believe these came before the bronze bearing models, I can't place why I think that. The patent # 81805 is stamped on the right side and under is a AL tag that says L7....I took that be a equipment take of the eventual owner.

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    Default Schaublin 70 Plainbearing

    Quote Originally Posted by Mcgyver View Post
    I acquired another Schaublin 70 recently, this is the plain bearing spindle model with the double taper at the inboard bearing - i think its 45 and 3 degrees. Previous hack operated with oil and the bearing seems really pooched, the owner was the type who was barely qualified to operate a lawn mower, not a fine machine tool, sad. Anyway, lamenting aside, there's scoring and it seems when you move the bearing all the way on the shaft, its still sloppy on the shaft - ie. there doesn't look like enough material to grind/lap it back in. afaik these are hardened and lapped steel bearings on a hardened and lapped shaft.

    I'd be ok attempting to make a part with one taper, but getting two tapers and perfect mate via lapping is something I'm not sure how to do or even if i'm up to it. So making a replacement bearing seems iffy.

    i'll contact Schaublin, but expect its an exercise.....if they have the part it'll likely be more than the lathe is worth in good condition. If thought of hard chroming the shaft, but then I'm back to 'how to lap a double angle conical bearing and its mate perfectly?"

    The lathe is otherwise pretty good, so i'd like to save it over parting it out.

    Any great ideas on solving this problem? Anyone converted one of these to roller element bearings?
    I have a such headstock. The base of the headstock is rescraped, not by me, so it is miss-aligned to a standard 70. The spindle is fine. The bronze bearings is worn. All parts is for sale if you think you can have use for it.
    P-O

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    Mcgyver,

    I am in the same boat as you. I have one ok plain bearing headstock and two with bad bearings. Mine are all from the 60's I have looked into re chroming the shaft, and it would be difficult to grind and i would still need to re lap the bearings. The Schaublin is a precision machine, it deserves a nearly perfect spindle.

    I have looked at converting the headstock to precision bearings, it Would be nearly impossible to make work. I do not think you could shove large enough bearing in the casting to guarantee an acceptable of rigidity. The ball bearing headstock castings are a bit larger.

    Ideally i would find an affordable ball bearing headstock for the 70. So, i think the best bet is to find a newer headstock. I would be willing to collaborate on a conversion also as i believe others have been down this path.

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    Quote Originally Posted by POAx View Post
    I have a such headstock. The base of the headstock is rescraped, not by me, so it is miss-aligned to a standard 70. The spindle is fine. The bronze bearings is worn. All parts is for sale if you think you can have use for it.
    P-O
    Any idea if new bearings are available? Then again if the bearing is worn, the shaft is going to have some wear, so will it mate properly with a new bearing? Do you have the OD of the bearings? I want to make sure they're the same - i.e. mine is earlier with the steel bearings.

    Quote Originally Posted by MCritchley View Post
    So, i think the best bet is to find a newer headstock. I would be willing to collaborate on a conversion also as i believe others have been down this path.
    Your points are solid on the challenges. Making that mating double taper, lapped, is a heck of a challenge. I've made taper mounts, where a taper meets a plane, and they're challenging enough.....add in two tapers and the very high precision and finish required...I'm just not sure how to do so, or if I could figure it out if its worth it.

    I'd like to collaborate on it, not really sure what direction to go. A batch of iron headstock castings that takes replaceable P4 angular contact bearings?

    I'm up for an interesting challenge but probably won't just buy a complete headstock. I hate buying stuff like that over ebay, condition unknown. Plus, I've got a couple of 70's so my heart wouldn't broken if I had to part it out (but thats not the preference). This is was rescue mission....still the idea of coming up with a slick fix appeals

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    an idea occured....grind the spindle shaft, the two tapers, 3 and 45 degrees. Take almost nothing off, but clean up. Then, lap. Lapping tapers (imo) requires making and charging a proper lap so the geometry is maintained (unlike a cylinder you can't move the lap back and forth so it doesn't self correct.). Grind it as fine as you can so the lap is mostly just putting the final polish on. Now, presumably, you've got a good shaft.

    For the bearing, instead of the original steel, do like latter models and make a bronze one. The difference being you just might be able to scrape it in, it would be tight space wise and you'd have to make some small bearing scrapers. The advantage is is eliminating one of the most difficult part of making a steel bearing, namely lapping to mate the double taper parts to a perfect fit.

    I'm very familiar with the very high standards of accuracy that one can achieve via scraping in the flat, but cannot claim the same experience with bearing scraping. It would seem the same principals would apply, with the small depth of cut and the right thinness of the blue, shouldn't it be possible to get the bronze bearing to with a tenth a perfect mate to the shaft?
    Last edited by Mcgyver; 05-19-2018 at 12:48 PM.


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