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Might need bearing lesson, tennis mach ver 2

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  • chipmaker4130
    replied
    Originally posted by Mcgyver View Post
    . . .7) I can't see why a preload is needed here, looks like straight radial loads and no reason for axial accuracy. . .
    Its not the axial accuracy he's trying to improve. Its the slop enabled by two ordinary bearings close together in non-precision fits, and the high-speed unbalanced rotating load applied some distance from the bearing. Pre-loading axially will indeed take most bearing-enabled wobble out, provided the inner and outer fits are improved with mounting compound.

    Leave a comment:


  • Mcgyver
    replied
    Originally posted by Mike Amick View Post
    That's a really nice summation Mcgyver, thanks.

    Between tightening up my tolerances and understanding bearings a bit more, I think I am getting it.

    Looks like a DRO is in the near future for my lathe, it's really hard (for me) to sneak up on those
    sizes with the dials, goes from almost there to whoops way to much to often.
    thanks and you are welcome. It is challenging work but doable. Agreed, its about impossible with a dial. I'd don't have a DRO on the lathe, but a tenths indicator on the cross slide works well for these more demanding jobs. The worse are high precision, smallish angular contact bearings with a tolerance range of about a tenth and half. Regular deep groove bearings are more forgiving. Bearing catalogues are slightly less painful than pins in the eye, but they do have all the info there and tolerances do vary by bearing size

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  • Mike Amick
    replied
    That's a really nice summation Mcgyver, thanks.

    Between tightening up my tolerances and understanding bearings a bit more, I think I am getting it.

    Looks like a DRO is in the near future for my lathe, it's really hard (for me) to sneak up on those
    sizes with the dials, goes from almost there to whoops way to much to often.

    Leave a comment:


  • Mcgyver
    replied


    1) don't used $1.50 bearings. For standard deep groove ball bearings the good ones aren't much money, NSK, SKF and so on. The good ones will be ABEC 4 or 5.
    2) the general rule, interference fit on the rotating part , and close sliding fit on the non rotating part
    3) the tenth tolerances sometimes required for that makes bearing fits demanding work, must hold your tongue just so
    4) Don't use an adhesive, makes it a pain to replace the bearings
    5) If you screw up on the fits, ok, use an adhesive, but make it loctite low strength cylindrical compound - the one specifically for bearings. You'll have fighting chance of getting it apart
    6) If you screw up, preferably make it on the bore not the shaft, you want the shaft the right press fit so it runs true
    7) I can't see why a preload is needed here, looks like straight radial loads and no reason for axial accuracy
    8) retaining the outer races with an internal shoulder and then a nut or snap right is SOP and works well
    9) it sounds like you have two bearings per shaft which should work fine

    Leave a comment:


  • A.K. Boomer
    replied
    Originally posted by chipmaker4130 View Post

    Unless there is a compelling reason to use cantilever shafts, the ideal solution is to go back to bearings on each end.
    Id have to agree with this, as beefy as he designed everything I still wonder about that channel-lock strut flexing under pressure and the repetitive shock loading of the bearings trying to cock even with loctite, Im sure it would prove to be "enlightening" watching a slow-mo vid of a ball getting squeezed and then launched with this machine...

    I did look at a popular brand name ( the Lobster) to try and get an idea of how they build these internally --- even went into an owners manual but they did not have any pic with the covers off of it....

    Leave a comment:


  • Bented
    replied
    Originally posted by chipmaker4130 View Post
    Don't bother looking up the ABEC7 bearings. Not appropriate for a ball chucker.
    You have ruined the joke, I only use ABEC 12 bearings when building CNC garden rakes.

    Leave a comment:


  • Mike Amick
    replied
    Click image for larger version

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ID:	1970141Ok, here is where I am at right now. I hammered out the current bearings (they were epoxied). Cleaned up the bearing seats
    Made a temp axle out of some stainless that is a better fit just to test it. So as it sits, the bearings are just sitting inside their
    area nothing holding them in.

    It spins real nice. So all I have to do is secure the bearings without moving them.

    And now, reading Rich's post about creating a preload. The bearing block is not bored all the way through, I just drilled
    a hole bigger than the axle, then i bore a ledge for the beraing to sit on. Your preload instructions are way more involved
    than I was expecting but will read it a copy of more times. .


    So here are the bearings just sitting there both sides of the black.running smoothly. Now I just have to glue or loctite the bearingws
    into bearing block with out messing up the allignment.

    Leave a comment:


  • Rich Carlstedt
    replied
    Mike
    I am not sure how your blocks are machined for the bearings.
    I assume it is a straight bore ?
    As such , You can preload the setup with three thin wall sleeves
    make a sleeve that fits inside the block bore and will be a spacer between the Outer races of the bearing
    For your bearings, a few thousanths under the 32 mm diameter will work and and maybe .050 to .100" thick.
    then make two thin sleeves for the shaft , slip fit and also only .050 to .100" thick and the lengths to be as follows.
    Measure from the roller to the bearing for one, and measure the bearing to the pulley and add a few thousandths.
    Install them and when you bring in the pulley, push it hard against the roller and then tighten the set screw.
    Your hand force axially will load the bearings before locking the position.
    Getting deep groove bearings will help your operation as well

    You most likely got ABEC -1 bearings..look for ABEC - 3 or 5
    Rich

    Leave a comment:


  • chipmaker4130
    replied
    Don't bother looking up the ABEC7 bearings. Not appropriate for a ball chucker. Ordinary deep-groove ball bearings can also be axially preloaded, best done with spring washers to avoid over tightening. Deep groove bearings (ordinary, everyday bearings) all have an axial load spec. you can use to make your design. There is a difference in same-size bearings. Some have a minimum complement of balls, some are nearly full. You'd have to ask your bearing supply house which is which.

    Unless there is a compelling reason to use cantilever shafts, the ideal solution is to go back to bearings on each end.

    Leave a comment:


  • oxford
    replied
    Just be forewarned, if you use bearing retainer Loctite, you will most likely destroy the bearings when it’s time to come apart.

    Leave a comment:


  • Bented
    replied
    Originally posted by Mike Amick View Post
    Ok ... both were from scratch. The main difference is the original one had bearings on both sides of the drive wheel. This time
    I used a thick block and have a bearing on both sides of the block. And the aluminum extrusion made things some what easier
    and it's a little expensive but not too bad.

    And AK, I think I will try and loctite the bearing to the axle and take your advice about spinning it and preventing it from settling into misalignment

    If that doesn't work I will make new axles that press fit.

    Also I will remember what Rich said about the outside bearing not needing to be pressed on.

    But I can't but think there may be better bearings to use, the ones i am using are like $1.50 a piece. 15mm

    Oh, real quick, how do I preload ?
    ABEC (Annular Bearing Engineering Committee) ,you preload the bearings by using pairs of angular race bearings pressed together much like a milling machine or lathe spindle.

    ABEC 7 bearings are wonderfully accurate and smooth running but cost well over $1.50.

    If making a prototype product do not go cheap, if a home project do not go cheap as you have experienced.
    https://www.grainger.com/search/powe...SAAEgLRFfD_BwE
    Good Luck
    Last edited by Bented; 11-13-2021, 06:45 PM.

    Leave a comment:


  • Rich Carlstedt
    replied
    Originally posted by Mike Amick View Post
    Ok ... .........................
    But I can't but think there may be better bearings to use, the ones i am using are like $1.50 a pi
    Oh, real quick, how do I preload ?
    Mike, there are two kinds of "Preload" , there is Radial Preload , and Axial Preload

    Radial is a function of the interference fit between the axle and the inner bearing race.
    For example, if the shaft was .0005" bigger than the Bearing ID , That would become the preload Radially on the bearing.
    You could consider the bearing inner race as being elastic and conforming to it's new diameter

    Axial Preload requires shims or adjustable nuts to shift the two bearings apart or together . That means if the inner races are rigidly locked in place, that
    the outer races be pushed inward or pulled outward from each other by using adjustable nuts or spacers. Sometimes spring washers are used as well.

    Rich



    Leave a comment:


  • chipmaker4130
    replied
    Originally posted by Mike Amick View Post
    . . .I think I will try and loctite the bearing to the axle and take your advice about spinning it and preventing it from settling into misalignment . . .
    The best way to achieve this goal is to apply the retainer and set the assembly with the shaft vertical. It doesn't take long for it to set.

    Leave a comment:


  • Mike Amick
    replied
    Ok ... both were from scratch. The main difference is the original one had bearings on both sides of the drive wheel. This time
    I used a thick block and have a bearing on both sides of the block. And the aluminum extrusion made things some what easier
    and it's a little expensive but not too bad.

    And AK, I think I will try and loctite the bearing to the axle and take your advice about spinning it and preventing it from settling into misalignment

    If that doesn't work I will make new axles that press fit.

    Also I will remember what Rich said about the outside bearing not needing to be pressed on.

    But I can't but think there may be better bearings to use, the ones i am using are like $1.50 a piece. 15mm

    Oh, real quick, how do I preload ?

    Leave a comment:


  • A.K. Boomer
    replied
    Originally posted by Rich Carlstedt View Post
    If you have machined and finish surfaces, then Loctite bearing retainer is possibility so you don't have to make the parts again. and it is applied to replicate a press fit

    Rich
    Good suggestion in fact they make a "stud and bearing mount" just for this type of purpose, I believe it's green and strong as all hell...

    If you have any clearance at all you want to apply liberally on both parts and "spin them together" if you can then let set up with "no load" not even gravity if you can help it as you don't want the fluid to go "eccentric" before it hardens....

    Leave a comment:

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