Adressing galled surfaces in gear assembly
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  1. #1
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    Default Adressing galled surfaces in gear assembly

    I have been taking my lathe apart to go through it and found some issues with a gear and the mating surface. Its a 1941 South Bend Lathe Reverse gear assembly. Its the main gear on that part.

    I have limited tools to address this issue, no mill, surface grinder or anything like that. I live in a machine desert. Any ideas how I should approach this? Would it be OK to run if I cant get all the grooves out of the surfaces? Are there any simple fixes to punt the problem down the road until I can address it properly?

    or any recommendations of where I might send this out to be re-surfaced if that is the only choice? Each hole has a bronze? bushing pressed into it but they all share the one plane in common so perhaps taking a thickness off the entire surface is the best course of action? I haven't tried to measure but maybe .020 would do it.

    Here are a couple pics of the assy before I pressed out the parts

    img_5834.jpg

    img_5836.jpg

    And the galled surfaces I am trying to address.

    rg14.jpg

    rg15.jpg

    rg16.jpg

    Thanks for any help or ideas!

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    Those groves are from lack of lubrication. If your in a dessert as you say, then lay some emery cloth on something flat and squirt some WD-40 or mineral spirits and rub the gear in a circle to dull the sharp edges. Or use a smooth cut file or sharpening stone. Then do the same to the bracket. Call around to some hardware stores and see if they have some nylon flat washers. You might get lucky and find one thin and a bigger diameter. If not order some from MSC or a buy a sheet of Nylatron. It;s self lubricated and cut a washer from, Or just file offthe burrs and oil it and put it back together if your a hobbyist. You may call around to outboard repair shops too, they probably have nylon washers.

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    Quote Originally Posted by Richard King View Post
    Those groves are from lack of lubrication. If your in a dessert as you say, then lay some emery cloth on something flat and squirt some WD-40 or mineral spirits and rub the gear in a circle to dull the sharp edges. Or use a smooth cut file or sharpening stone. Then do the same to the bracket. Call around to some hardware stores and see if they have some nylon flat washers. You might get lucky and find one thin and a bigger diameter. If not order some from MSC or a buy a sheet of Nylatron. It;s self lubricated and cut a washer from, Or just file offthe burrs and oil it and put it back together if your a hobbyist. You may call around to outboard repair shops too, they probably have nylon washers.
    Thanks for the reply! I was wondering if I could get away with a washer. Are there any minimum thicknesses I should be shooting for if I go that way? Also how about the O.D. of a washer if I cut my own? Would it be better to have it larger to spread the contact area?

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    I agree with Richard in how to deal with the two parts, but I'd prefer to use a thin, hard metal shim in place of the nylon washer, both to keep the change of distance minimal, and to give a longer life wear surface when there'll still be some roughness present (you won't be sanding down .020").

    Perhaps a thinned version of one of these (they have other sizes) would do the job.

    McMaster-Carr

    It might take assembling the lathe, facing a washer to ~.020", then washer installation.
    Or buy some bronze shim stock in the right thickness and turn a usable OD and ID.

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    Default Cleaned up the galled gear surface

    I cleaned up the gear thanks to the suggestions in here, thanks. I used new mill file with some wood paint stirrers as guides to keep it level and took my time to take down most of the grooves with some WD40 as cutting fluid.

    p1050006.jpg

    p1050005.jpg

    Then I cleaned it up a bit more with a hard oil stone. I don't know if all of this was necessary but I felt like I was advancing the cause and doing my best work! It came out real nice.

    p1050007.jpg

    p1050010.jpg

    I wasn't able to clean up the body of the assembly very well it had a lot of damage. I put a washer in between the parts but have not pressed it back together. I wanted to see what you guys have to say about this first. Would you be comfortable running the lathe with this kind of a band-aid?
    I found a 1/16 thick nylon washer but I would have preferred one with a larger OD. I can make a nice bronze spacer once the lathe is up and running.

    p1050011.jpg

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    Forget the washer, just put it back together. Squirt a little oil on the gear train once in a while and you'll get another 70 years worth of use out of the lathe and gear train before it needs attention. Sometimes having those little grooves from wear and tear can help you in lubrication. There is no side loading on the gear train, just there to keep it from coming off the shaft.

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    ^^^yes, lose the washer, and When you press it back together cut a u shaped shim .002" thick to slip between the gear and casting, pull it out when done to give it running clearance(.001" at both ends) so oil can get in there, keep it oiled and there will be essentially no metal to metal contact.

  10. Likes 4GSR, Kevin T, ballen liked this post

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