Schaublin 70 plain bearing is pooched - ideas....or part it out?
Close
Login to Your Account
Results 1 to 19 of 19
  1. #1
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    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?

  2. #2
    Join Date
    Feb 2010
    Location
    ch
    Posts
    2,048
    Post Thanks / Like
    Likes (Given)
    187
    Likes (Received)
    269

    Default

    what year is the machine?

  3. #3
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    Default

    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.

  4. #4
    Join Date
    Feb 2010
    Location
    Sweden Linkoping
    Posts
    164
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    68

    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

  5. #5
    Join Date
    Mar 2007
    Location
    Milwaukee
    Posts
    366
    Post Thanks / Like
    Likes (Given)
    299
    Likes (Received)
    173

    Default

    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.

  6. #6
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    Default

    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

  7. #7
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    Default

    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 01:48 PM.

  8. #8
    Join Date
    Aug 2005
    Location
    South Australia
    Posts
    173
    Post Thanks / Like
    Likes (Given)
    7
    Likes (Received)
    27

    Default

    Hi Mcgyver, giving your problem a bit of thought .. I'd clean up the spindle by grinding 'tween centres assuming the end bevels that Schaublin used to do it are still ok. DON'T lap on any account ..HONE manually using a single small flat fine stone, in other words 'superfinish' to polish only taking off the grinding finish crests no actual 'stock' removal. Now also assuming the headstock bores are pristine coz you've removed the bearings by chilling them (haven't you?), I'd turn up new bearings in say O1 steel to appropriate under & oversizes. Internally grind the bores, parallel rear & double taper front as near as possible then internally hone as for the spindle, no lapping. Same technique, small straight stone/s, inner taper first testing the 'figure' with bearing blue adjusting with localised attention to high areas. Once the inner taper mates & outer taper is beginning to witness work on both the same way. The thing about reasonably soft honing stones is they will adapt fairly quickly to the general macro shape of the work while knocking off the tiny deviating high spots. You CAN get both tapers to register, the main thing is to forget you can't. When you have the front bearing fitting the spindle nicely adhere it to the spindle wrung on with shellac or if you have a solvent, Loctite 290. I have a very old drum of highly sulphurised cutting oil that dissolved 290 with ease. Then I'd grind the OD of the bearing using the spindle as a mandrel between centres to either a light press fit in the headstock or else a fine Loctite fit. For what it's worth.

  9. Likes Mcgyver liked this post
  10. #9
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    Default

    swarfless,

    thanks for the thoughtful response. I needed some time to ponder. Can you expand a bit on two points, 1) why no lapping and 2) why not the bronze.

    Any lapping I'd do would be with a ground and charge lap, no free floating abrasive, so I'd think i'd get even cutting?

    For grinding, my equipment is light. Motorized work on a t&CG.....I scraped the T&CG so it is really good, but its still light compared to a proper grinder. For internal, its tool post on the lathe. Partially why I was thinking of scraping the bearing.

    You've got me thinking.....just trying to understand the finer points

    thanks

  11. #10
    Join Date
    Feb 2010
    Location
    Sweden Linkoping
    Posts
    164
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    68

    Default

    Mcgyver, You have the right way to go in swarfless post. The spindle I have is already cleaned up in a Studer grinder. The centers is still there. I would suggest to make bearing "blanks" in over sized bronze. Then scrape the front bearing to fit the spindle. Mill and drill the oil groves. I think the rear bearing can be turned to fit the spindle cylidric part. Then just turn the bearings OD with the spindle as mandrel like svarfless way. To hand scrape bearings to fit the dubble taper will go fine as you can handle the spindle and bearings separated from the headstock casting. I would avoid all abrasive operations in this case.

  12. Likes Mcgyver liked this post
  13. #11
    Join Date
    Aug 2005
    Location
    South Australia
    Posts
    173
    Post Thanks / Like
    Likes (Given)
    7
    Likes (Received)
    27

    Default

    Hi Mcgyver. Shake brother, I too am limited to T & C grinder but do have internal attachment. My remarks were how 'I' would go about it. I'm not averse to bronze or scraping it BUT I think Schaublin's machining something worthy of reliance, so one would assume their headstocks to be line-bored pretty right .. I'd take maximum advantage of that. Get the spindle clean & true, get the bearing bores fitting that & then the ODs of the bearings true to that again & assemble, that's the philosophy. No lapping, honing only with conformal stones: here we adopt the technique of the optical finisher to some extent, the 'figure' has already been established by our machining the little refinement to be accomplished by polishing more than anything. Why I prefer keeping with the hardened steel bearings, the work will be slow & tedious but Unlikely to go backwards, ever better. The honing would only amount to 'superfinishing' i.e. very short oscillation & only moderate pressure so as not to crown the surface worked on. Vary your technique to correct any tendency to crown or hollow, i.e. dwell at the ends to correct hollowing or dwell at centre to correct crowning. Admittedly a short soft lap would work simarly but 'I' wouldn't use diamond coz it works faster than my little mind. Only reservation concerning bronze is it demands scraping solely & while I've done both in different applications THIS job I'd do as described. Grinding the bores of the bearings by tool post grinder ought to be fine, you'd fix up the concentricity & axial truth of the ODs by subsequent grinding on-the-spindle between centres. I just happen to think scraping the bronzes in-headstock more tedious & there is the possibility of working directional bias into their alignment. Of course you COULD scrape the bearings to the spindle before turning their ODs ON-the-spindle between centres just like the grinding of the hardened bearings .. still relying on Schaublin's line-boring for the final alignment

  14. Likes Mcgyver liked this post
  15. #12
    Join Date
    Aug 2005
    Location
    South Australia
    Posts
    173
    Post Thanks / Like
    Likes (Given)
    7
    Likes (Received)
    27

    Default

    Seems POax hit on the treatment of the bronzes before I did. Amen.

  16. #13
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    Default

    Quote Originally Posted by swarfless View Post
    Of course you COULD scrape the bearings to the spindle before turning their ODs ON-the-spindle between centres just like the grinding of the hardened bearings .. still relying on Schaublin's line-boring for the final alignment
    thanks guys. ......100% on the same page re strategy: clean up spindle, put a fine finish on it, machine then fit bearing, fasten to shaft and grind OD, all relying on Schuablin's bearing mount geometry.

    Still thinking about bronze vs hardened steel, later models were bronze, so it wouldn't be un-Schuablin to do so. otoh it is a small deep bore to scrape, likely a lot easier to talk about than do, so that pushes me toward steel.

    The rear bearing is a collet like affair, not a simple piece but it seemed more doable if I could figure the front out. I suppose it does hold its challenges. I'm think after heat treating, make a cone for it to fit in, cement in, grind and finish ID, then remove and glue to shaft to grind OD taper.

    On heat treating the bearings - leave it fully hardened or a slight, say straw anneal? Any reason to prefer O1 to say A2? Default would be heat treat myself (have an oven), but doesn't have to be.

  17. #14
    Join Date
    Aug 2005
    Location
    South Australia
    Posts
    173
    Post Thanks / Like
    Likes (Given)
    7
    Likes (Received)
    27

    Default

    Hi Mcgyver, O1 is what came to mind because that's my first choice personally for ease of heat treatment in my home shop .. muffle furnace & a bucket of oil. I guess A2 is even simpler but I have no experience with it. As to hardness/temper I would temper it back a bit if only for stability.. about 400F for ~ 60 RC according to ASSAB. Realise I didn't explain aversion to lapping here .. you can't reciprocate a conical lap to even out the polishing but a small partial flexible shell such as a piece of PVC conduit say 1/4" shorter than the internal taper bridging say 1/3rd the larger periphery so that it needs to be flexed into contact OR a small soft hone (India) of similar length but quite narrow, say 1/4", that will quickly form a conformal shape while shuffled back & forth ~ 1/4". You'll need to hold your mouth right, but it is doable. For the external cones similar but the PVC conduit would need to be smaller in diameter than the small end of the cone so that it has to be flexed to fit. You could make several laps like that loaded by rolling in finer grades of carborundum grit, say start with #600 or # 800 & go finer. Obviously the PVC conduit needs to be thin walled, some other PVC tubing might be found. A small soft stone again would quickly conform to the male cone/s shuffling it back & forth 1/4". 'I' would probably use ~ 100-200rpm & apply pressure with a finger while OHS isn't looking or you could make up a 'wand' of some sort to keep the pinkies clear. Naturally I like your approach to the rear bearing. Duhhh I just realised a small brake cylinder hone, the DIY variety with floating shoes might be just the trick for the internal cone, the acute one, with the spring loading set light. Better stop at this point .. a dedicated machine might suggest itself ..

  18. Likes Mcgyver liked this post
  19. #15
    Join Date
    Feb 2010
    Location
    Sweden Linkoping
    Posts
    164
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    68

    Default

    Mcgyver, To scrape a bronze bearing, in this case, would not be to hard to do. You can turn the blank to fit the spindle, so good it will blue mark the bearing blank on both taper surfaces. then you just have to scrape the bearing to get the best oil/lubrication function.

  20. Likes swarfless, Mcgyver liked this post
  21. #16
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    Default

    Quote Originally Posted by swarfless View Post
    Hi Mcgyver, O1 is what came to mind because that's my first choice personally for ease of heat treatment in my home shop .. muffle furnace & a bucket of oil. I guess A2 is even simpler but I have no experience with it. As to hardness/temper I would temper it back a bit if only for stability.. about 400F for ~ 60 RC according to ASSAB. Realise I didn't explain aversion to lapping here .. you can't reciprocate a conical lap to even out the polishing
    Story of my life, it all needs a dedicated machine. I'm so deep in the loop of making to make things I'm not sure where its supposed to all be going anymore

    anyway, on lapping. Not meaning to tell the choir how to sing, but I'll explain where I was coming from. I've done cylindrical lapping (mostly internal) with great success using an expanding lap covered in copper and loose slurry. When you get to the finer grits the "feel" is very fine, and lap itself, also being cut by the slurry ends up an accurate cylinder lets that lets you lap a very accurate cylinder. in my experience you can get bores of consistent diam to a few microns as measure with a dial bore gauge.

    That is NOT what i'm think for here, because of your point that the lap cannot axially move in the taper. If you use loose abrasive you'd get goodness knows what geometry as the lap wore away with the work stuck in the same axial position. What I'm think is a proper lap, just for the internal bores, precision ground to the geometry wanted and then charged with abrasive, then cleaned. No loose abrasive.

    A decade ago I made a rotating lap of cast iron for carbide scrapers. I check it last night and the surface of the cast iron is in perfect condition, just like it was machined. i.e. the carbide scrapers have never made contact with the cast iron. The experience says the textbook is right; a properly charged lap with no loose abrasive will maintain its geometry. If I grind the perfect shape in say soft steel, charge with 10 micron diamond paste, wash it, than use it (even by hand) with a bit of oil I think it would work. Still doesn't solve the challenge of the double taper though.

    I'm leaning more toward your approach....just wanted to explain myself so you didn't think I was one of the loose abrasive cannons wanting to throw it in between moving parts and hope for the best


    Quote Originally Posted by POAx View Post
    Mcgyver, To scrape a bronze bearing, in this case, would not be to hard to do. You can turn the blank to fit the spindle, so good it will blue mark the bearing blank on both taper surfaces. then you just have to scrape the bearing to get the best oil/lubrication function.

    My reservation about scraping is its a bit restricted space wise. I've done lots of scraping of machine tools (but not bearings) so have a sense what is possible, but trying to get down into the bottom on the small dia 3 degree taper might be difficult especially with final pointing, I'm viewing it as a way to fit the double taper not lubricate (the Schaublin steel and bronze bearings were as smooth as can be allowing the shaft to ride on the thin wedge of oil).

    I really appreciate the help and input you guys, its definitely helping! It will be a time consuming and challenging task (for me anyway) so am taking it slowly

  22. #17
    Join Date
    Aug 2005
    Location
    South Australia
    Posts
    173
    Post Thanks / Like
    Likes (Given)
    7
    Likes (Received)
    27

    Default

    Hi Mcgyver, yes I know where you're coming from, have followed a lot of your exploits as have been aired. You COULD make a compliant taper lap. Picture an arrow head with the acute edges replicated by little parallel bars held off the head by a little compression spring each end. The 'arrow head' could be two bladed or better three bladed. With identical springs throughout the loading on the bars .. well you get the picture. It would be good to locate the bars radially, on guide pins perhaps? Need to keep grit away from them to prevent jamming. The bars could be cast iron preferably but copper or aluminium would do. Roll the abrasive in, wash off the xs & Bob's your uncle..
    Last edited by swarfless; 06-01-2018 at 08:48 PM. Reason: spelling

  23. #18
    Join Date
    Aug 2005
    Location
    South Australia
    Posts
    173
    Post Thanks / Like
    Likes (Given)
    7
    Likes (Received)
    27

    Default

    As to scraping, you grind a small slim taper triangular file to make a three-square scraper & go for it .. if you decide on bronze bearings.

  24. Likes Mcgyver liked this post
  25. #19
    Join Date
    Aug 2005
    Location
    Toronto
    Posts
    4,953
    Post Thanks / Like
    Likes (Given)
    2929
    Likes (Received)
    3242

    Default

    Quote Originally Posted by swarfless View Post
    As to scraping, you grind a small slim taper triangular file to make a three-square scraper & go for it .. if you decide on bronze bearings.

    I was looking at it yesterday, probably not as difficultly tight as I was thinking and I have a small bearing scraper as well as the triangle files prepared for it, so I'm all set. I'm still thinking about it (lots to finish first) and still thinking fitting the double taper would be a challenge via grinding. Maybe a combination - stoned super finish on shaft and the bearing is then scraped to fit it? I know ground surface aren't the best to blue from, so there's that, but I could glue the bonze on after scraping and grind OD as you suggest. No heat treating and the fit is so control-able .....we'll see

    Its an interesting subject as there is applicability to countless small lathes, watchmaker variety. When the bearings go they're considered scrap afaik where as the Schaublins are a little more special, but at some as the supply runs out fixing these will matter.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
2