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  1. #21
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    Feb 2007
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    Quote Originally Posted by Skyfire View Post
    Yes. pretty much as you said. just like the "fixed" end for ballscrews.

    I guess one single tapered roller bearing on each end will work too considering strongger than angular contact ones. But safe MAX speed I guess should around 3000-4000RPM because the MAX RPM of ID45mm tapered roller bearing should be around 6000. Just a guess.

    BTW. In the benchtop building thread in this forum, I will use the angular contact bearings for the spindle the same way as I did. I think it can reach MAX 6000-8000RPM with P5/P4 class bearings. I think it will work well too. but the initial target of this spindle is 3000RPM now. I will see then.

    Cheers~
    What do you think about using a pair of double-row angular contact bearings back to back at the nose of the spindle and preloaded from the front, then a single floating radial bearing at the rear for supporting drive belt loads?

    The stack of double-row angular-contact bearings would be 61mm (2.401") long, and 85mm (3.346") in diameter. The spindle body I'm working with is only 152mm (6") long, so the radial bearing would be fairly close to the A/C bearings.

    This configuration is probably the easiest to machine as everything can be done from one side of the headstock block in a single setup.
    Gough Custom - http://goughcustom.com/

  2. #22
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    Quote Originally Posted by mactec54 View Post
    aarongough

    My post here may give you a idea of how to make one, this is a smaller diameter than what you want, but you can make it just larger to suit your spindle

    http://www.cnczone.com/forums/cnc_wo...dle_build.html
    Ah, I remember that ER16 spindle build. Beautiful work!

    Those labyrinth seals look simpler than I would have thought! I thought they had to have multiple back-and-forths (like two combs fitted together) but it seems that you're only using 2?

    If that's enough, then I could certainly work something like that into the design.
    Gough Custom - http://goughcustom.com/

  3. #23
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    Some additional great information of building spindles here: Lathe Spindle Bearings, and design.
    Gough Custom - http://goughcustom.com/

  4. #24
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    Hmmm...

    So, I've been doing some research while waiting for other tasks to finish at work and I think I've had a revelation about how preload works that will make this spindle more difficult to build.

    When using a matched pair of angular contact bearings the inner and outer races are ground to different widths so that when pressure is applied to the 'stack' as a whole the bearings acquire their correct preload once they are jammed up against each other.

    I was going to simulate this with deep-groove ball bearings by placing a slim spacer between the faces of the inner races. Unfortunately though that means that I would also have to place a spacer between the outer races of the pair, otherwise the nose bearing will have the rear of it's outer race unsupported, and the stack will not be rigid.

    This is only a problem with the 3 bearing configuration (two axial/radial bearings at the nose, one radial bearing at the heel), when using a 2 bearing system then the bearing pockets at the front and back of the spindle allow you to apply preload across the whole stack with no risk of a bearing race ending up unsupported...

    If I make the spacer between the inner races very small (equivalent to the entire preload distance) then I can do away with having to make an outer spacer. But the tolerances required there are more than likely far beyond my abilities, and adjustments would be a nightmare as they require re-sizing the spacer.

    From what I'm seeing this pretty much rules out the option of using a pair of deep-groove bearings at the nose, unless I'm missing something.

    The remaining options are 3 bearing config with a matched pair of A/C bearings at the nose, or a 2 bearing configuration with separate bearing pockets at the front and rear of the headstock.

    Am I missing anything with my thinking here guys?

    I guess this explains why most of the manual lathes I've seen use a 2 bearing configuration, to avoid using a matched pair of A/C bearings that would be responsible for a big chunk of the cost of the lathe...
    Gough Custom - http://goughcustom.com/

  5. #25
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    I guess my final question here is: Is it really a problem if one face of a bearing race is unsupported?
    Gough Custom - http://goughcustom.com/

  6. #26
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    Lots of good info on bearing grades etc, here: Ball Bearing Primer - VintageMachinery.org Knowledge Base (Wiki)

    I'm trying to make note of the pages I use for research so that others can get hold of it easily.
    Gough Custom - http://goughcustom.com/

  7. #27
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    Jan 2005
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    aarongough
    double row angular contact

    Double row angular contact bearings, that you have most likely found, you can not add any preload, they are preset, they do have backlash, this is a very small amount around .0005, there are some that have a split inner race that can be preloaded, but these double row angular contact bearings, are not what you want to use for your spindle


    I've seen a number of spindle designs with the dual bearings at the nose, but they've all been smaller spindles

    It does not matter what size the spindle is big or small, all the good one's are constructed the same way
    Mactec54

  8. #28
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    Sep 2006
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    I've attached a couple of drawings of the spindle from my standard modern 13" x 34" lathe that show it using a double timken roller bearing assembly at the nose and a standard deep groove bearing at the tail.




    hope this helps a bit with visualizing the arrangement.
    Mike

  9. #29
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    Quote Originally Posted by mactec54 View Post
    aarongough
    double row angular contact

    Double row angular contact bearings, that you have most likely found, you can not add any preload, they are preset, they do have backlash, this is a very small amount around .0005, there are some that have a split inner race that can be preloaded, but these double row angular contact bearings, are not what you want to use for your spindle

    Interesting! The fact that you can't properly preload double-row bearings makes perfect sense when I take a second to think about it! Thanks for pointing that out!

    Quote Originally Posted by mactec54 View Post
    I've seen a number of spindle designs with the dual bearings at the nose, but they've all been smaller spindles

    It does not matter what size the spindle is big or small, all the good one's are constructed the same way
    Well, I guess that I'm building a 3 bearing spindle then!
    Gough Custom - http://goughcustom.com/

  10. #30
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    Quote Originally Posted by ninefinger View Post
    I've attached a couple of drawings of the spindle from my standard modern 13" x 34" lathe that show it using a double timken roller bearing assembly at the nose and a standard deep groove bearing at the tail.

    hope this helps a bit with visualizing the arrangement.
    Mike
    Thanks Mike!

    this is very similar to the small spindle designs that I have seen, I was just never able to dig one up for a lathe! Thanks for taking the time to post that.

    Interestingly I notice that the inside faces of the inner bearing races are unsupported, which answers my question from before about whether that is ok or not!
    Gough Custom - http://goughcustom.com/

  11. #31
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    Put some time in today putting together a draft of the headstock assembly design.

    Any thoughts on the general arrangement?

    The 2 blocks in front of the nose bearing comprise the bearing shield, and could be adapted into a labyrinth seal if needed.

    The bearings stack isn't as long as I'd like, but I don't have any more spindle length left!
    Attached Thumbnails Attached Thumbnails headstock-assembly-cutaway.jpg  
    Gough Custom - http://goughcustom.com/

  12. #32
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    Jan 2008
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    A thought for the 6209 preload spacer... I've done similar for the top pulley of a step belt Bridgeport mill.

    The required spacer will depend greatly on the actual bearings you get - they are not all the same. Clamp them together with some small blobs of soft solder or lead in the center race faces. The solder will compress and measurement of this will indicate the actual differential space required to get to approximately "neutral" preload. That's your starting point.. then add "10ths" (not"thou") for actual preload.

    The process to get a reliable preload without overload can be quite time consuming. Too much and you'll rapidly overheat the bearings; too little and they'll flop around. Are you sure you don't want to just get some 7209SU bearings? These are angular thrust (not matched pairs) and already have differential grind applied - just clamp togther... Not expensive at all unless you want matched precision class.

  13. #33
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    Quote Originally Posted by lakeside53 View Post
    A thought for the 6209 preload spacer... I've done similar for the top pulley of a step belt Bridgeport mill.

    The required spacer will depend greatly on the actual bearings you get - they are not all the same. Clamp them together with some small blobs of soft solder or lead in the center race faces. The solder will compress and measurement of this will indicate the actual differential space required to get to approximately "neutral" preload. That's your starting point.. then add "10ths" (bit "thou" for actual preload.

    The process to get a reliable preload without overload can be quite time consuming. Are you sure you don't want to just get some 7209SU bearings? These are angular thrust (not matched pairs) and already have differential grind applied - just clamp togther... Not expensive at all unless you want matched precision class.
    I'm certainly amenable to that if the deep groove bearings aren't going to work. I'd love to use sealed bearings as I'm worried about being able to keep the crud out of them, but if it's not possible then I have to roll with the punches!

    Which letters in the bearing descriptor indicate that they have the differential grind? I normally buy bearings from VXB, the closest that I can find on their site is this: 7209BMU Nachi Angular Contact Bearing Brass Cage C3 Japan 45x85x19 Ball Bearings
    Gough Custom - http://goughcustom.com/

  14. #34
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    The -SU (in SKF, FAG, etc speak). It means univeral grind, but on an individual bearing rather than as a precision matched pair. The Nachi -BMU is the same.

    Seals as found on the 6209 won't last in a spindle environment. Use the BMU / SU and put a laberyth seal or whatever in front.

    There are very few sealed angular thrust bearings. I've used some sold as "aircraft magneto" bearings, but they cost a small fortune.. You'd be looking for bearings JM209WI PP3 DULxxxx or similar.


    Here's a set of super precsion - not much more than you'd pay for the Nachi Barden 209HDL Super Precision Bearings SKF 7209 CD P4ADGA | eBay

  15. #35
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    Thanks for the input Lakeside! I hadn't thought about using eBay as a source for bearings, I had been looking at various online stores only.

    If I can get a matched pair like that for $150-200 then I'll just do that, seems like a much better idea than fooling around with other methods that may not work!

    I'm constantly amazed at the sheer level of expertise and experience that CNCZone as a community can bring to bear on any given topic. Pretty amazing! And greatly appreciated!

    I'll update the design to show a back-to-back pair of A/C bearings.

    Not sure quite yet how I'm going to machine the labyrinth seal. Do you think that the shield/seal shown in the drawing is enough, or I would need to add more 'labyrinths'?

    My final question is: how do I design an oil system for this spindle? It's probably only going to be run up to about 3-4K RPM, would a partial oil bath work? Or would I have to devise some system for dripping oil into both bearings?
    Gough Custom - http://goughcustom.com/

  16. #36
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    Buy Barden's precision bearing grease (about $30 a 30cc tube). Look up their data for the amount (it's very small) and put exactly that amount in. Too much and it will overheat. Seal up and forget about it.

    For the labyrinth - my Emco (not Enco) has similar sized bearings and a disk about 4mm thick placed direcly in front of the bearing, with 3 peripheral grooves. This disk is about 0.2mm smaller than the bearing OD.

  17. #37
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    Quote Originally Posted by lakeside53 View Post
    Buy Barden's precision bearing grease (about $30 a 30cc tube). Look up their data for the amount (it's very small) and put exactly that amount in. Too much and it will overheat. Seal up and forget about it.

    For the labyrinth - my Emco (not Enco) has similar sized bearings and a disk about 4mm thick placed direcly in front of the bearing, with 3 peripheral grooves. This disk is about 0.2mm smaller than the bearing OD.
    Great! Sounds like the grease will make life much easier.

    Does the headstock housing on your Emco have matching tongues that go into the peripheral grooves? Not sure that I'm quite picturing what's going on...
    Gough Custom - http://goughcustom.com/

  18. #38
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    2100
    You could certainly use a hydraulic oiler of some kind, but I think that's way overkill for a lathe spindke. The old school way of oiling a lathe spindle bearing is to have an oil sump inside the spindle head, and a splash oiler. You just drain and refill the sump periodically. A more modern hi tech solution might be to use an air tool oiler and spray an oil mist continuously into the head creating positive pressure. This virtually guarantees that no dirt gets past your labyrinth seals. I would probably go with the sump and the splash oiler myself. It should give you some ideas to think about anyway.

    PS If any of this looks a little funny, it's because I'm using voice to text on my phone to reply. Not because anything I said was stupid. Lol!
    Bob La Londe
    http://www.YumaBassMan.com

  19. #39
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    Quote Originally Posted by Bob La Londe View Post
    You could certainly use a hydraulic oiler of some kind, but I think that's 1 way overkill for a lathe spindke. The old school way of oil in a lawn spindle bearing is to have an oil sump inside the spindle head, and a splash oiler. You just drain and refill the sump periodically. A more modern hi tech solution might be to use an air tool oiler and spray and oil mist continuously into the head creating positive pressure. This virtually guarantees that no dirt gets past your labyrinth seals. I would probably go with the sump and the splash oiler myself. It should give you some ideas to think about anyway.

    PS If any of this looks a little funny, it's because I'm using voice to text on my phone to reply. Not because anything I said was stupid. Lol!
    One of the things I was originally going to include was positive air pressure inside the spindle housing. I think now that it might be overkill, but the idea of it is very elegant!

    Lakeside pointed out that greasing the bearings should be fine for the RPMs that I'm running at, which is something I hadn't previously considered. That looks like it will make life much easier!

    My biggest worry right now is the labyrinth seals. If they do need many convolutions, then they may be beyond my ability to manufacture. We'll see how that turns out.

    PS: The voice-to-text on your phone seems to work well!
    Gough Custom - http://goughcustom.com/

  20. #40
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    Jan 2008
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    They are just a disc with a few grooves in the outer edge. The bearing housing bore is the other surface, 0.1mm away... Grease in the grooves keeps the junk out. Make sure any design has has an amospheric relief path. i.e. the inside of the bearings is at the same pressure as outside. If not... they will puke out grease when hot and suck in crap when coolling.

    Emco's use tapered bearings front and back with preload applied by a rear nut. Dead simple, robust and works very well... Copied by the Chinese for decades!


    This is the spindle from and Emco Compact 10 (11x26 center to center) I'm converting to cnc. It has an MT5 taper and a D1-4 spindle mount. It was unused and in storage for 25 years. Minor surface rust and dried out grease. After these pictures I restored it to "like new".




    And the rear




    There is a thin metal sheild behind the bearing cup that is a moderately close fit to the shaft. The bottom of the casting is open.




    Note the seal at the front. You can make a more complex seal but it really isn't needed unless you are blasting high pressure coolent at it.



    Spindles don't come much simpler that this. The devil is of course in the details... very accurate machining. This simplicity is copied in many small Chineses lathe, but they just don't perform the same as the original Austrian implementation.. and don't cost as much either!

    Then there's way more complex... my TUM35 lathe (14x40) has a d1-4 spindle... with 7 bearings front to back. 2 P4 tapered rollers, 2 p5 thrust bearings, 4 deep radials and a spherical bearing as a rear outer support! $2000 just for bearings...



    And.. Think about how you will assemble and disassemble the spindle without "bashing". You above see glimpes of the special puller/pusher I made for this job - basically a threaded rod, but it does have a thrust bearing and a bunch of parts (including an MT5 insert) for centering etc.

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