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  1. #261
    Join Date
    Aug 2007
    Posts
    558

    Guldberg, no advice from me - you look to have things well in hand!

    Just wanted to say thank you very much, I'd never thought of having the whole spindle part of the headstock separate :idea: That's going to make my lathe a whole lot easier to build! Fantastic...

    Steve - I didn't realize bronze bearings could work so well. I'm re-thinking my design now. I'm surely going to go with the separate spindle-in-headstock idea, but maybe I should drop the AC bearings and go for bronze... Could you tell me what you're using for a thrust bearing? Would higher RPM be a bad idea with your setup?

    Anyone want a set of 7212 AC bearings?

    Thanks again to you both,

    Jason

  2. #262
    Join Date
    Mar 2004
    Posts
    1661
    Quote Originally Posted by S_J_H View Post
    The plain bearing is a remarkably simple and extremely accurate way to go.
    I agree on that. Every car engine got 'em.
    They also have a greater area to take the load. Roller bearings are supernice, but may not be needed. I've said it before though - I do like overkill engineering.

  3. #263
    Join Date
    May 2006
    Posts
    573
    Thanks for all the inputs

    I really like the idea of bronze bearings, there is something "old school" about them, in a good way that is. Though for now I will stick to ball bearings, since this is a know territory for me. Also im shooting for some higher rpms in the range of 10000.

    As for the whole double mounted angular bearings, I have followed many spindle building threads where this has been discussed and I have even build a spindle using this design. The reason I choosen the current design is the simplicity, where the bearings are hold in place by the spindle itself. Most conventional lathes seems to work fine this way, proberly because you dont really do production runs anyway, so distortion in the spindle rarely affect the work. Im sure i could live with this distortion, but i think im going to redesign it anyway to accomondate the dual angular bearing in the busy end and with a single support bearing in the drive end.

    I hadnt given the position of the drive belt a thought until now, but now you mentioned it, I think ill do that pully arrangment vertical of the spindle, makes good sense.

    So far I have the spindle, the bearings, a ER32 collet chuck, a 3 jaws chuck and a 4 jaws independent chuch, so for now ill stick to this spindle. A barfeeder and a pneumatic/hydraulic chuck/collet would be nice though, but thats going to be a whole new project:-)

    Edit: I just had a look at the spindle, its designed for opposite mounting of the bearings, as in my current design, so there is no room for two bearings at the same end, nor any possible way of fixing the bearings agains each other. I will stick with the current design, as for the bearings. Since the spindle is interchangeable, i may take on the quest of designing my own some day in the future, without having to redesign the headstock

  4. #264
    Join Date
    Mar 2006
    Posts
    357
    Steve - I didn't realize bronze bearings could work so well. I'm re-thinking my design now. I'm surely going to go with the separate spindle-in-headstock idea, but maybe I should drop the AC bearings and go for bronze... Could you tell me what you're using for a thrust bearing? Would higher RPM be a bad idea with your setup?
    Jason, I still am using the factory ball thrust bearing. Here is a link with further details- http://www.lathes.co.uk/southbend9-inch/page3.html
    There is a fiber thrust bearing on the opposing side. Many now replace that with a needle bearing assembly.

    Rpm is limited without using a pressurized system. I would not feel very comfortable pushing it beyond 1500rpm. Unless I was doing some small diameter work with carbide tooling I don't have much need for much more rpm out of it.

    Steve

  5. #265
    Join Date
    May 2006
    Posts
    573
    The other day the machine went flyving. While it was hanging there I mounted some of the vibration dampning feets.

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    Also I started my epoxy/granit adventure. First a trip to various stores to buy the parts needed
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    Keen to try it out, i cooked some gravel and sand in the oven:-)
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    But when i got home and had a look at the epoxy fill at Bob Warfields site (http://www.cnccookbook.com/CCMillEpoxyFill.htm), my sand looked way to fine and the gravel to big, so the next day I went out and bougth another bag of more coarse sand. I did a quick test using Bobs formular. The result came out okay, but it doesnt look as good as Bobs. The more brownish color im sure is do to the dust in the sand, which is actually crushed rock. I may just use this formular with a little less epoxy, say 12%, its only for dampning, not for structual use. I may also buy some finer gravel and make another triel. Bob suggested to do a couple of test batches with water to find the right amount of epoxy. Anyway, comments are appreciated

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    BTW does anybody know if this thing is still toxic when its hardend?

  6. #266
    Join Date
    Jul 2003
    Posts
    586
    you mean to eat .........or do you mean the off gassing time period?

  7. #267
    Join Date
    May 2005
    Posts
    2502
    Looks fine to me!

    Fun making those "mud pies" isn't it?

    Easy stuff to work with, though it is very toxic while wet. It promotes an allergic reaction that gets worse every time it contacts your skin. Though I wore gloves and safety glasses, some snuck by and left some nasty welts for a time.

    I am convinced this will be a great addition to your lathe, especially given it is weldment and not cast iron.

    That thing is going to be built like a tank when you're done!

    Cheers,

    BW

  8. #268
    Join Date
    Feb 2006
    Posts
    1072
    Except on a tank, the composite armor is usually on the outside.

    Another impressive build, Jacob. Thank you for your extensive documentation!

    Randy

  9. #269
    Join Date
    Aug 2008
    Posts
    573
    From my reading of the Epoxy Granite thread, it seem the ideal mixture contains a range of aggregate, each part smaller than the previous to obtain a filler than is >80% solid and <20% epoxy (Ideally it requires degassing and vibration at >2G but that is probably unnecessary in your case).

    [I've been hunting back through the pages to find the most useful single post]
    http://www.cnczone.com/forums/showpo...postcount=3575
    http://www.cnczone.com/forums/showth...30155&page=288
    Bill

  10. #270
    Join Date
    May 2005
    Posts
    2502
    Quote Originally Posted by BillTodd View Post
    From my reading of the Epoxy Granite thread, it seem the ideal mixture contains a range of aggregate, each part smaller than the previous to obtain a filler than is >80% solid and <20% epoxy (Ideally it requires degassing and vibration at >2G but that is probably unnecessary in your case).

    [I've been hunting back through the pages to find the most useful single post]
    http://www.cnczone.com/forums/showpo...postcount=3575
    I think that thread is dedicated to not having a most useful single post, LOL.

    But it is quite fascinating.

    The approach I took was to minimize the epoxy use experimentally. Think of the epoxy as just being a binder. The thread guys (last I looked a long time ago) were trying to calculate optimal formulations mathematically.

    It turns out not to be hard to make good progress empirically.

    Collect what aggregates (gravel and sand) are readily available to you. Grab a scale too. Now start mixing various proportions by weight. Keep careful records. For each formulation, place the dry mix in a cup and slowly add water until you have water at the top. Record the before and after weight of the water containing to know how much you've used.

    All you're trying to do is use the least amount of water by weight. The water is measuring the "holes" in the aggregate that will have to be filled with epoxy.

    If you research the commercial mixes, some get as low as maybe 9%. But their main goal in going so low is that epoxy is expensive. It's quite easy to experimentally get down to say 12%. The difference between 9 and 12 won't matter much for the performance of your machine, but it will cost you some epoxy. The thing is, by the time you buy a bunch of fancy aggregate grades, epoxy additives, vacuum chambers, and vibrators for de-airing, you can pay for the extra epoxy and get on with it.

    In particular, buying graded aggregate so your theoretically optimal mix can be realized ain't cheap. You're likely shipping rocks around. Get a "good enough" mix from local materials. It works great and really dampens the machine.

    The details of all this are here on my page:

    http://www.cnccookbook.com/CCMillEpoxyFill.htm

    Eventually I will run some scientific tests of performance as I have one filled IH mill and one not. But I had to take the spindle motor off the unfilled to get the filled going. When I put a bigger motor, belt drive, and VFD, I'll put the old motor back on the other mill and run some tests. I can already subjectively tell a pretty good difference though.

    Cheers,

    BW

  11. #271
    Join Date
    Aug 2008
    Posts
    573
    I think that thread is dedicated to not having a most useful single post, LOL.
    Yes, I know what you mean

    Get a "good enough" mix from local materials. It works great and really dampens the machine.
    That's a good point Bob - The 'anglo-american epoxy granite working group ' AKA ckelloug and greybeard are doing a fantastic job researching into a structural material but if all you need is a mass-damping filler then the empirical approach should work well.
    Bill

  12. #272
    Join Date
    Mar 2004
    Posts
    1661
    Quote Originally Posted by Guldberg View Post
    Thanks for all the inputs

    I really like the idea of bronze bearings, there is something "old school" about them, in a good way that is. Though for now I will stick to ball bearings, since this is a know territory for me. Also im shooting for some higher rpms in the range of 10000.
    Now hold on a minute (or at least a second)!
    Old school? As I said, these kind of bearings are in 99,999% of all petrol engines produced. My last roadracing motorcycle, straight out of the box, had a red revline by 16500 RPM.
    Just wanted to point that out. Now go continue with your new school bearings.

  13. #273
    Join Date
    Apr 2006
    Posts
    169
    hi Guldberg ask in your area for sand for swimming pool filter you can find different size
    ready sorted an clean

  14. #274
    Join Date
    Feb 2008
    Posts
    521
    Quote Originally Posted by svenakela View Post
    Now hold on a minute (or at least a second)!
    Old school? As I said, these kind of bearings are in 99,999% of all petrol engines produced. My last roadracing motorcycle, straight out of the box, had a red revline by 16500 RPM.
    Just wanted to point that out. Now go continue with your new school bearings.
    I think 'bronze bearings' is a bit of a misrepresentation here?. When used in IC engines and the like, the bronze's is primary role is as a backer shell for the lead/tin/alloy bearing face. They don't actually bear any load at all - that is taken by the oil film between the 'bearing' and the rotating part. Bronze or oilite bronze bearings are more bushes that can support low load, low speed rotating parts, try getting the rpm's up in the k ranges or remove the oil pressure from a lined shell bearing and see how well they survive - usually measured in seconds! Back to the thread!

  15. #275
    Join Date
    Mar 2006
    Posts
    357
    I think most of us are indeed talking about hydrodynamic plain bearings. Oillite bronze bearings are usually used as a bushing and have no place in a machine spindles headstock. The shell of a plain hydrodynamic bearing can be made of many things. It is the oil film that is really at work.
    Many OEM engine bearings are now silicon aluminum with steel backing.

    Bronze alloys work well in machine tool spindles as a bearing with non pressurized lube but so does good old cast iron. Rpm is limited as without pressure the oil film breaks down at speed. But up to that point they are operating with the hydrodynamic oil film which is why they run so smooth and friction free.
    Pressurized plain bearing turbos can spin to unreal speeds (100,000 + rpm.)

    It would be neat to build a pressurized plain bearing system for a lathe but it's a whole lot easier to just buy some ball bearings and call it a day.

    Here is a good link if anybody wants to pursue using plain bearings in their machines-
    http://www.bearings.machinedesign.co...emech_a04.aspx

    Steve

  16. #276
    Join Date
    Sep 2006
    Posts
    6463
    Hi all, most people don't have the necessary skill or equipment to produce plain bearing set-ups that really work.

    The ideal plain bearing set-up would be pressurised with proper filtering, seals and an oil recovery system.

    The other side of the coin is you won't find it in the cheaper machinery because it's too costly in manpower to make.

    Retrofitting ballbearings in existing plain bearing set-up is usually not possible due to the ball bearing being too big in the outside diam for the housing.
    Ian.

  17. #277
    Join Date
    May 2006
    Posts
    573
    Yesterday I started the actual filling of the base, I can honestly say that, that didnt went very well. On the way to the workshop i stopped by an aqariumshop and bought another bag of sand and gravel. The sand is cleaned and looks/feels better, also the gravel are smaller than what I previously bought. I started the filling with a 12% epoxy mixture and fin- tuned it along the way and ended up at 15% epoxy, 25% sand and 60% of the fine gravel (5-8mm). This was all fine until the epoxy started pouring out through the cracks in the base! Quite optimistic I counted on the epoxy being thick enough to not flow to the cracks, but man was i wrong:-) Soon there were epoxy all over the table. I tried to stop it with a silicone fillet, but with little luck. Im glad I used a 15% formular, maybe some 10% is still left. Anyway, I went crazy with the silicone, so at least now the rest of the compartments are sure to be tight.

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    I did a little experiment, added some ironoxid to the mixture. Intended for coloring paint, it seems to work just fine for this type of application. Comes in all kinds of colors

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  18. #278
    Join Date
    Jan 2006
    Posts
    481
    Guldberg............ awesome build keep up the great work! What sort of budget have you allowed for the project build ?

    Cheers

  19. #279
    Join Date
    May 2006
    Posts
    573
    Budget??? :-) According to my better half im using way to many money on my projects. Im just buying stuff as I build, I will rather wait untill the next paycheck and buy the stuff I really need, than buy some cheeper stuff. I have no clue of the total cost so far, maybe one day ill add it all up if im going to sell it.

  20. #280
    Join Date
    May 2006
    Posts
    573
    All the bays filled. Rough calculation tells me that i added 40kg to the whole construction. Now I just have to figure out how to get it back on the stand

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    Ive learned a lot from this experince, one of which is that this sticky stuff gets everywhere

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