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Thread: Bearings

  1. #31
    Registered User Little Scrapper's Avatar
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    Re: Bearings

    Quote Originally Posted by VP1 View Post
    Nice little bearing Mike. I could see myself using these in my Chilton. What's the ID (bolt size) and where'd you get them?
    R3 ZZ PRX from Grainger. It's a 3/16" bearing. On my first post in the thread you can see the bracket if you'd like. Looking forward to setting this up.

    Bearing width is .194"

  2. #32
    Registered User mcrae0104's Avatar
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    Re: Bearings

    Quote Originally Posted by ScaleBirdsScott View Post
    Fun fact but since I happen to be staring at a poster here at work with the lineup, the SSN575 Seawolf, the second ever nuclear sub, was commissioned in 1957. (Nautilus was 1954)

    It's all "ancient" history as far as I'm concerned, having grown up in the 90s and all; but fun to keep those things in parallel. I'd imagine "aircraft" grade bearings date back to, say, the 30s?
    Scott, take a look at current headlines re: nuclear missiles in eastern Europe. I offer no commentary, except to say, what was old is new again.
    ​simplify.

  3. #33
    Registered User BBerson's Avatar
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    Re: Bearings

    I was thinking .001" interference fit. Probably correct info online or Machinery Handbook.
    They usually stake the bearing in place with a light center punch on the radius edge.

  4. #34
    Moderator Dana's Avatar
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    Re: Bearings

    .001 is too much press for a bearing that small. I have a chart for the small Torrington/Fafnir bearings at work, I'll post it if I remember.

    Nowadays the plastic bearings are so good I'd consider that instead of bronze. I've had very good results with Igus plastic bearings on the machinery I design.
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  6. #35
    Registered User wsimpso1's Avatar
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    Re: Bearings

    On my airplane parts, I rarely get the finished size I bought the reamer for. Some reamers make a hole a little bigger than they are supposed to produce, while some reamed holes in material with only a little meat around the outside end up smaller than they are supposed to be. Boring on a mill is the only way I have found my stuff to be right on.

    I end up punching the perimeter (3 or 4 places, evenly spaced) and/or gluing (LocTite for penetrating assembled parts) my bearings.

    For install, I have made simple press tools for the housing and bearing on a lathe and use a small press where I can. When the press won't work because of clearances, etc, I drill the centerline of the press tools and make a rod from 4140 to pass through the bearing or set, thread it, and close the assembly with a wrench on nuts. I make the support end with recesses to suit the installed position of the bearing surfaces in the housing on that end. For install, both end pieces can be the similar. If you ever want to remove it, you may also need a support end cut to clear the bearing and a driver small enough to go through the bore. Oh, and all of these need a relief for any protruding hub or inner race.

    Billski
    Billski's opinions expressed here are available free and may be worth the money you paid for them. Understand that they are based upon a successful combination of education and a lifetime of experience using that education, but I can not know everything about your circumstances. Your choices are yours alone, and you must be the final judge on what you do. No whining...

  7. #36
    Registered User BJC's Avatar
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    Re: Bearings

    IF you have an inner race that protrudes on both sides, that is good. Ensure that the aileron, etc., fitting clamps to the race, so that the only rotation is in the bearing, and not between the bolt and the bearing. Shim with washers to constrain axial movement.


    BJC

  8. #37
    Registered User blane.c's Avatar
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    Re: Bearings

    The best bearings in the world are "Timken".

    https://www.timken.com/

  9. #38
    Registered User Little Scrapper's Avatar
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    Re: Bearings

    I'm not looking for the best, I already have the bearings.

    The inner race does not protrude so I'm sure I can use some thing bearing shim washers?

    I found reamers that are half a thou under so figured that would work. Maybe I'll just buy a cheap one and experiment. That's half the fun I suppose.

  10. #39
    Registered User Little Scrapper's Avatar
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    Re: Bearings

    Here's a quick sketch and a photo of the bearing next to a dime to reflect just how little it is.

    Click image for larger version. 

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  12. #40
    Moderator Dana's Avatar
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    Re: Bearings

    Looks like you want the housing to be 0-.0007" undersize for a press fit, and the shaft to be .0002-.0006 undersize for a slip fit on the shaft.

    Note that the chart also shows the max/min shoulder sizes to avoid interfering with the moving parts.

    Click image for larger version. 

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  14. #41
    Registered User Dan Thomas's Avatar
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    Re: Bearings

    Quote Originally Posted by Little Scrapper View Post
    I bought a couple of these bearings for the ailerons, pretty small. $4 each. Pretty cheap as well.

    Attachment 78845

    This is a pressed bearing in to a piece of aluminum. I've pressed bearings but never anything this tiny. I've chilled bearings, and heated the receiving part to fit, but again nothing even close to this small.

    The bearing has a O.D. of .500" and I'm thinking of getting a undersized reamer that's .4995"

    Thinking about chilling the bearing and boiling the aluminum bracket and using a small arbor press to press them in. Slight chamfer on the aluminum bracket.

    To keep it square while pressing I was thinking of turning a part that's basically a shouldered pilot block.

    I'm looking for someone with experience to double check my idea and process. Am I missing anything? These bearings are tiny so I'm a bit out of my element.
    .0005" interference is minimal and you wouldn't likely need to shrink them in. They should push in fine. Cessna stakes the aluminum around theirs so they can't escape. Their bellcranks tend to be a bit thicker than the bearing is wide to enable staking. I've installed bearings like this with a bit of Loctite 272 (red stuff), but I rough up the OD of the bearing a little so the Loctite can grab it, and make sure everything is oil-free.

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  16. #42
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    Re: Bearings

    1/2 thousandths will provide plenty of interference on a .5" dia part.

  17. #43
    Registered User Dan Thomas's Avatar
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    Re: Bearings

    Quote Originally Posted by Turd Ferguson View Post
    1/2 thousandths will provide plenty of interference on a .5" dia part.
    Normally, yes. But pressing or shrinking it into a bracket with only 1/8" around half of it will stretch that thin secion and reduce the pressure on the bearing. It should hold ok though.

    Now. What is that bracket made from? 2024T3? 6061T6? 7075 of some sort? It matters. 6061T6 would stretch easily. 2024T3 would be tighter and 7075T6 might split because it's so hard and brittle.

  18. #44
    Registered User proppastie's Avatar
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    Re: Bearings

    You have the bearing captured between the L fittings....The Bracket is also captured between these fittings,...There are no safety issues if the bracket were to be even be a loose slip fit over the OD of the bearing... Now a small bearing with a thin race can be distorted by too much press fit. .0002 to .001 press should be fine You will need to buy a ream and if you are really anal a pin gauge.

  19. #45
    Registered User fly2kads's Avatar
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    Re: Bearings

    Quote Originally Posted by Dan Thomas View Post
    Now. What is that bracket made from? 2024T3? 6061T6? 7075 of some sort? It matters. 6061T6 would stretch easily. 2024T3 would be tighter and 7075T6 might split because it's so hard and brittle.
    It's specified as 24ST, so 2024 in today's nomenclature, presumably T3.

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