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  1. #1
    Join Date
    May 2003
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    Central Coast, NSW
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    Default Getting some bearings onto a shaft

    Hi. I’m making a pottery wheel. This should be an easy project, and indeed making the frame out of scrap timber, mounting a clutch motor and electrics has been easy, but as usual I’ve come to a grinding halt building the drive shaft.

    The problem is getting the bearings onto the shaft. I obtained a milled stainless steel 1/2 inch shaft, and bought a couple of 1/2 inch bearings in cushion blocks (name ???), a v-pulley and belt. The plan was to drive one bearing on just a short distance, but the other one has to be driven about 100mm down the shaft. I’ve been trying to do this for hours and so far I’ve only managed to get it about 10mm. I’ve applied all the force and hammer blows I can prudently apply, and also heat, but it just won’t move.

    So my questions are :
    Is there some trick to this?
    Is it even possible to get a 1/2 inch bearing on a 1/2 inch shaft in a DIY situation?

    I’m reasonably happy with one bearing. It hasn’t gone on far but it doesn’t have to. I’m thinking perhaps I should cut the other bearing off with an angle grinder, go buy a new one, sand or file the shaft down by about 0.5mm or until the new bearing slides easily, and rely on the two bearing grub screws to keep it in place. I know that’s shoddy and I can’t expect a genuinely round shaft if I attack it manually with a file, but what is the alternative?

    Cheers
    Photo of shaft with bearings attached.72C15DBF-48BC-4376-8853-D5645B9F984F.jpeg
    Apologies for unnoticed autocomplete errors.

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  3. #2
    Boringgeoff is online now Try not to be late, but never be early.
    Join Date
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    Default

    If you can drive the shaft back out of the bearing with a drift, you might be surprised how little you have to file the shaft down to make it fit properly. Get a black marker pen and colour the shaft all round to the length you want to reduce. File all the colour off, try the bearing for fit, and repeat the process until it does fit.
    Cheers,
    Geoff.

  4. #3
    Join Date
    May 2011
    Location
    Albury
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    3,019

    Default

    What are you using to drive it, perhaps a piece of appropriate sized pipe? Did you use a bit of grease on the shaft? Might be best to take it off with a bearing puller and start over.

  5. #4
    Join Date
    Feb 2006
    Location
    Perth
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    Default

    When you say a 1/2" shaft do you mean 0.5", 0.50" or 0.500" - the same goes for the bearings.

    You have to first know what those measurements are (and you have to check in more than one place) otherwise you will be beating your head on a brick wall.

    If they are both exactly 0.500" then a bit of heat (hot air gun) on the bearing might be enough to expand the bearing enough for it to slide on.

    If the shaft is just marginally over the bearing diameter it won't work and then you will absolutely have to reduce the shaft diameter,
    It might be possible to use wet and dry to get the shaft diameter down but you won't get it down by 0.5mm this way - you might get it down by 0.01 mm by putting the shaft on a lathe with the end of the shaft poking out and running the wet and dry (suggest oil rather than water) up and down the shaft.
    To get it down by 0.5mm you will have to use a MW lathe.

    In your application (low rpms) the bearing and shaft don't have to be a hard fit so using the grubs screws should be OK but not 0.5mm different, - maybe something like 0.1mm at most.

  6. #5
    Join Date
    Jun 2010
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    They are called pillow block bearings and those grub screws are designed to allow the bearings to be fitted to undersized shafts, eg a 1/2” bearing on a 12mm shaft. The actual limitations on shaft size would be published by the bearing manufacturer. Another use of the grub screws is to allow the shaft to be mounted vertically, which is what you will be doing with a potter’s wheel. When you eventually position the bearing where you want it mark the grubscrew locations on the shaft and carefully drill some indents in the shaft for the screws to locate into, this stops the screws “smearing” the shaft material and making the bearing just as hard to get off as it was to put on.

    Your shaft is obviously too fat for the bearing but there is a solution. Purchase some good quality emery cloth strip in 120 grit (eg Norton) about 20-25mm wide and use that to slowly polish the shaft to the size you want. Start off at the very end of the shaft and use Geoff’s Texta tip to work out the high spots until the bearing can start to be pushed onto the shaft. Once the first inch or so has been done wrap the cloth completely around the shaft (like a bow drill) and keep working it up until the bearing gets to where you want it. Emery “blunts” fairly easily so you’ll probably go through a couple of meters but using something like Simple Green or Windex as a lubricant will help it last longer and speed up the process. If you can’t get thin strip buy some 50mm/2” and simply tear it down the middle.
    Nothing succeeds like a budgie without a beak.

  7. #6
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    Albury
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    He's got the bearing on the shaft, it's not .5mm different.

  8. #7
    Join Date
    May 2003
    Location
    Central Coast, NSW
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    3,330

    Default

    Now you come to mention it, I never actually measured the shaft myself, but relied on the experts 😉 at the men’s shed and the bearing shop. So, pulling a micrometer out, the shaft measures average 12.73 mm, with a range from 12.71 to 12.74.

    I don’t have the technology to accurately measure the bearing internal diameter,however if it’s machined accurately then I guess it should be 12.70.

    Would that extra 0.03mm be enough to make it such a difficult fit?

    Anyway, Given the advice I’ve received above, and the fact that there doesn’t seem to be any secret bearing-mounting methods I didn’t know about, I’ve decided to extract the shaft and thin it down. I don’t have access to a either a metal or a wood lathe now so it will have to be by hand. I can only do a limited amount of hand work (old injuries) so it will have to be a brutal job with a file followed up by limited sanding. I’ve painted it to let it dry overnight to give me some visual guidance. My main question now is what would be the size I should head for, to be quite certain that it will go on smoothly. Maybe a maximum of 12.60 perhaps.?

    As one poster above mentioned, a pottery wheel is not a high speed or high stress application, so I’m prepared to overlook a minute bit of shaft wobble just to get this over and done with.

    Thanks for the help so far.
    Cheers
    Arron
    Apologies for unnoticed autocomplete errors.

  9. #8
    Join Date
    Apr 2015
    Location
    Brisbane
    Posts
    304

    Default

    If you do use heat/cold, you need to warm the bearing and put the shaft in the freezer. Back in the day of lead light with real light bulbs, you could put the bearing on the lead light wire cage for a while to warm(but not overheat) it.
    As other are saying, better to take a small amount of material off the shaft.

  10. #9
    Join Date
    Apr 2014
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    Little River
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    As you don't have a lathe you can spin the shaft with a drill to sand it down.

    Leave one bearing on the far end clamped down to stop the shaft moving around too much.

  11. #10
    Join Date
    Jun 2010
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    I really wouldn’t use a file on this, emery cloth is much safer and will allow you to creep up on the required size. We are only talking about 30 minutes work here to bring that shaft down to size using 120 grit.

    If you would struggle to hold the two ends of the cloth and pull it back and forth due to your injury you could quickly construct a bow out of any flexible material such as thin timber slat or plastic conduit, even a Quick-Grip clamp set as a spreader would do. Staple the cloth together in a loop (lots of staples or HD carpet joining tape) and wrap one side around the shaft, then put the ends of the loop into the ends of the clamp or whatever you make the bow out of.
    Nothing succeeds like a budgie without a beak.

  12. #11
    Join Date
    Feb 2006
    Location
    Perth
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    Default

    Quote Originally Posted by Arron View Post
    Now you come to mention it, I never actually measured the shaft myself, but relied on the experts  at the men’s shed and the bearing shop. So, pulling a micrometer out, the shaft measures average 12.73 mm, with a range from 12.71 to 12.74.

    I don’t have the technology to accurately measure the bearing internal diameter,however if it’s machined accurately then I guess it should be 12.70.
    Well you got one end of the shaft on - if you can get it off and measure the shaft that went on you will have an idea of what the bearing internal diameter is.

    Would that extra 0.03mm be enough to make it such a difficult fit?
    Yep

    My main question now is what would be the size I should head for, to be quite certain that it will go on smoothly. Maybe a maximum of 12.60 perhaps.?
    I wouldn't bother about size just keep taking take it down with emery cloth or wet and dry until it fits.

    Shaft in the freezer is a good idea, provided you have a freezer that is big enough.

  13. #12
    Join Date
    Jun 2005
    Location
    Helensburgh
    Posts
    7,696

    Default

    Quote Originally Posted by Arron View Post
    Now you come to mention it, I never actually measured the shaft myself, but relied on the experts  at the men’s shed and the bearing shop. So, pulling a micrometer out, the shaft measures average 12.73 mm, with a range from 12.71 to 12.74.

    I don’t have the technology to accurately measure the bearing internal diameter,however if it’s machined accurately then I guess it should be 12.70.

    Would that extra 0.03mm be enough to make it such a difficult fit?

    Anyway, Given the advice I’ve received above, and the fact that there doesn’t seem to be any secret bearing-mounting methods I didn’t know about, I’ve decided to extract the shaft and thin it down. I don’t have access to a either a metal or a wood lathe now so it will have to be by hand. I can only do a limited amount of hand work (old injuries) so it will have to be a brutal job with a file followed up by limited sanding. I’ve painted it to let it dry overnight to give me some visual guidance. My main question now is what would be the size I should head for, to be quite certain that it will go on smoothly. Maybe a maximum of 12.60 perhaps.?

    As one poster above mentioned, a pottery wheel is not a high speed or high stress application, so I’m prepared to overlook a minute bit of shaft wobble just to get this over and done with.

    Thanks for the help so far.
    Cheers
    Arron
    Ask on the metal working forum if there is anybody who can do it for you, even a woodworking lathe is usable to do this.
    CHRIS

  14. #13
    Join Date
    May 2003
    Location
    Central Coast, NSW
    Posts
    3,330

    Default Progress made, tumore help needed

    Ok, using the advice given here, what i did this morning was cut off one of the bearings, go to the bearing shop and purchase a new one, and then manually thinned the shaft down.

    Unfortunately, I didn’t check it against the bearing until I had removed a little too much metal (newbie mistake, didn’t realise how little removal was needed). I had taken it down to 12.61 mm, +/-0.02mm, so now I have a shaft a little too thin by about 0.1mm. This doesn’t matter with the bearing because the grub screws take care of the tiny bit of slack, but there is also a v-belt pulley to be mounted on the same shaft. The pulley doesn’t have any grub screw, but I would like to use it anyway as I won’t be able to source a new one till after Christmas. Is there a sneaky Trade-secret fix for this, a way to get an aluminium pulley to grip a slightly undersize shaft and stop slipping?

    And another question. I need to buy a belt to go between the motor and the shaft. Both have v-belt pulleys. How do I calculate the size needed? If I wrap a piece of string around, so that it is hard up against the inside of both pulleys, and then remove and measure then the total length is 580mm, so that I guess is the inside measure of the belt needed, but I have a belt marked 585mm and it is way smaller.

    Cheers
    Arron
    Apologies for unnoticed autocomplete errors.

  15. #14
    Join Date
    May 2012
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    Woodstock (Cowra)
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    Default

    Belt size is measured on the OUTSIDE of the belt,
    If you have the ability to drill and tap a hole in the pulley do that for a small diameter screw, if it has a head, cut it off and cut a small slot in the end to tighten with a standard screwdriver but remember to file or grind a small flat area on the shaft for the screw to tighten against otherwise under load and time the pulley will slip spin on the shaft, alternatively drill a hole through the pulley and shaft and pin with a friction fit pin or roll pin. A piece of a soft drink can will take up any slack between the pulley and shaft if it fits,
    The person who never made a mistake never made anything

    Cheers
    Ray

  16. #15
    Join Date
    Jan 2005
    Location
    Campbelltown NSW
    Age
    77
    Posts
    335

    Default

    Is it possible to drill and tap the pulley to take a grub screw? And either drill a dimple or file a flat on the shaft to stop the pulley slipping.

    For the pulley belt can the motor be mounted on a slotted hole bracket for adjustment to suit the belt.

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