Obsolete Bearing Replacement
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  1. #1
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    Default Obsolete Bearing Replacement

    Hi all.

    I'm working on a Sidney Lathe (thread here) and the change gear bearings are totally worn out to the point where the hardened sleeve has partially disintegrated. I've looked fairly far and wide and I cannot find anything close, and if I could it would be very expensive. If you know of a special something that would do feel free to look, but I don't think it exists anymore. I don't have the exact width, but the ID is 3/4", the OD is 1 9/16" and the width is roughly 1 1/2". The thrust is handled by nothing more than the gear sliding against the frame and outer washer.

    So, what I'm thinking of doing is replacing it either with a set of ball bearings or with a bronze bushing.

    If I did the bushing:
    1. What type of bronze? SAE 660?
    2. What should my wear surfaces be? A 1 9/16" bushing pressed into the gear running on a hardened steel bushing clamped onto the stud? A smaller bushing just running on the 3/4" stud?


    For the bearing replacement I was looking at using R12 ball bearings as they have the right ID and the OD is only large by 1/16". I kind of drew up a plan of how I would do it. Please excuse the fact that the drawing quality sort of falls apart. Left Side is current, right side is my plan.

    My current plan of attack:
    • Bore the gear to about 1.624 leaving around 1/8" of the original diameter towards the back.
    • Press in a 7/16" wide R12 2RS bearing with the inner shield removed
    • Press in a 5/16" wide R12 open bearing
    • Make a spacer with an internal groove and hole in it so that grease can always flow into the bearings
    • Press in another 7/16" wide R12 2RS bearing with the inner shield removed
    • Use a very thin washer against the inner race to keep the outer washer from rubbing on the gear and outer bearing race.
    • When clamped with the nut all the inner races and spacers should be snugged up tight and will not be able to slide on the stud, and there will be just a whisker of space between the frame and the outer washer.

    Sound like a good idea, or no?

    If I did the bearing:

    1. Should I space the two outer bearings out as much as possible like shown even though the shell gets pretty thin near the outside? Or should I place them inward, to where they are right under the line of radial force from the gear?
    2. Should I neglect the middle bearing if I space them outward?
    3. The book says gears are between 48-50 HRC. Will I be able to bore these with carbide or will I need CBN?
    4. Indicate off the teeth or the bore? Shouldn't matter I'd reckon.








    Thanks in advance.

    PS, I read the rules and I know it says not to talk about bearing replacements here. I figured since this is a non-standard replacement that requires some re-engineering and maybe permanent modification of obsolete parts, I'd best ask the machine rebuilding experts. If I'm wrong please move my thread and I won't do it again.

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    Machine the gear for back to back tinkins, with a spacer in the center...Phil

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    I'm not a machine tool rebuilder but I used to be a repair machinist before covid...
    I would bore each side of the gear for a .oo1 ish slip fit on your sealed bearing leaving the center .200 ish smaller than the od of the bearing
    I would not remove the grease seals from the bearings
    A washer to get the gear lined up and a spacer between the inner races and your good IMHO

    Ive made this repair many times sometimes the bore has to be sleeved or welded up.
    As far as cutting 50 rc I doubt the hub is hard usually it's just the teeth but you never know
    Any real insert should cut 50 easy
    Hss would if you go slow enough
    Good luck

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    Quote Originally Posted by Phil in Montana View Post
    Machine the gear for back to back tinkins, with a spacer in the center...Phil
    Tapered rollers seem like an unnecessary expense since there is no thrust component. I looked them up anyway, and it seems like the od would be too large and the gear would get very thin if it worked at all near the outside.

    Quote Originally Posted by Hbjj View Post
    I'm not a machine tool rebuilder but I used to be a repair machinist before covid...
    I would bore each side of the gear for a .oo1 ish slip fit on your sealed bearing leaving the center .200 ish smaller than the od of the bearing
    I would not remove the grease seals from the bearings
    A washer to get the gear lined up and a spacer between the inner races and your good IMHO

    Ive made this repair many times sometimes the bore has to be sleeved or welded up.
    As far as cutting 50 rc I doubt the hub is hard usually it's just the teeth but you never know
    Any real insert should cut 50 easy
    Hss would if you go slow enough
    Good luck
    Definitely some good suggestions there. I didn't even think to go from both sides. Appreciate it.

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    I d go with needle roller bearings,if the load was high ,if low ,then a full width solid ,or sintered bronze bushing.......Solid bronze needing regular lubrication,as in grease,or a few drops of oil per day..........Needle rollers can be fitted just about anywhere ,but custom sleeves will be needed to avoid cutting hard steel components.......You might getaway with the drawn cup type,which are very economical.

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    I would machine the hole one diameter through and trough That is the easiest
    You could hone it to size even then Or use emery cloth on a stick
    2 Seegerrings in the ID of the bore and a spacer between the innerraces of 2 (RS type) bearings
    No more than 2 bearings
    Spacer here and there if need be

    Peter

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    Quote Originally Posted by john.k View Post
    I d go with needle roller bearings,if the load was high ,if low ,then a full width solid ,or sintered bronze bushing.......Solid bronze needing regular lubrication,as in grease,or a few drops of oil per day..........Needle rollers can be fitted just about anywhere ,but custom sleeves will be needed to avoid cutting hard steel components.......You might getaway with the drawn cup type,which are very economical.
    I did look up needle bearings after your post but I didn't find anything I really was fond of. I'd need at least two of the ones I found to get the width right and then with the hardened inner sleeves you're looking at close to $80 or something.

    Quote Originally Posted by Peter from Holland View Post
    I would machine the hole one diameter through and trough That is the easiest
    You could hone it to size even then Or use emery cloth on a stick
    2 Seegerrings in the ID of the bore and a spacer between the innerraces of 2 (RS type) bearings
    No more than 2 bearings
    Spacer here and there if need be

    Peter
    Machining all the way through would require that the gear be held in position only by an interference fit on the bearings, I'd like to be held a bit more solidly, like with Hbjj's suggestions about the shoulders. Does require twice the setup though.

    Any more opinions before they go under the knife? Thanks to everyone btw.

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    [QUOTE=ClappedOutBport;3569660


    Machining all the way through would require that the gear be held in position only by an interference fit on the bearings, I'd like to be held a bit more solidly, like with Hbjj's suggestions about the shoulders. Does require twice the setup though.

    Any more opinions before they go under the knife? Thanks to everyone btw.[/QUOTE]

    The seegerrings (or snaprings) will keep the bearings in place
    It is effectivly a shoulder

    Peter

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    Keep it simple.

    When that needle bearing was new it probably had more play than a new chinese ball bearing.

    I suggest using just ONE sealed ball bearing. Look to see if they make a double row bearing in the same size you need. If it's cheap, buy that.

    The stamped idlers on vehicle belt drives use single chinese 6203 bearings and go hundreds of thousands of miles at 5000+ RPM. A single bearing would last 1 billion years in that gear.

    1635-2RS is a very common bearing with a 3/4" bore you can often find locally for $10.

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