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Thread: Crafting your own bench grinder / polisher

  1. #1

    Lightbulb Crafting your own bench grinder / polisher

    Hi all. I am thinking of buying a set of pillow blocks / mandrels, a nice grinding wheel, a belt, and a motor and making my own grinder.
    My reasons: I already have a motor. I like the simplicity and challenge of the build. I would really like a nice blue norton 3x wheel but don't want the whole system to break the bank. I would ideally like an 8" wheel but want slow speed. I believe if I understand the physics correctly that a grinder run off a belt would actually spin slower than even the direct arbor slow speed market grinders (picture a half rotation of the motor sheave, then compare that to the larger arbor sheave, it goes maybe only a quarter of the way, so your slowing it even further. And to start I already have a 1750 rpm so I could probably make an 8" wheel have a surface speed close to that of a slow speed 6" wheel.

    I figured I could make a pretty good set up with some high quality mandrels and hardwood. I see Lee Valley has some and Brownells has some. Does anyone have experience with any of these, or others? The Lee Valley is appealing because I trust their quality and they look nice, but they are only 1/2 inch which I'm worried may be smaller than ideal (though i know the one way balancing system does offer a 1/2 inch mandrel adapter).

    Thanks for any advice and/or shared experiences.


  2. #2
    I have been considering something similiar. I have a Woodcraft 8" slow speed (1750) grinder that works OK but; it has some bearing noise and run-out. I think that I can build a set-up that will be smoother for much less $ than buying a top quality grinder. I don't have any input on the pre-fabbed mandrels that are currently available. Be sure to include a belt guard to cover that arbor sheave.
    When failure is not an option
    Mediocre is assured.

  3. #3
    Join Date
    May 2008
    It's been a long time since I've looked in a Brownells catalog, but I know everything they sell is top quality. If you have a choice of rubber mounted or solid mounted pillow blocks I'd pick the solid mounts.

    As for the speed of the wheel it's simple math to figure the ratio of the motor sheave to the arbor sheave to reach the desired rpm.

    Good luck and keep yourself out of the belts and sheaves.

    Confidence: The feeling you experience before you fully understand the situation

  4. #4
    Join Date
    Oct 2005
    Helensburgh, Australia
    I have given thought to doing the same thing for different reasons. Use a three phase motor and a VFD and you have instant speed adjustment for different purposes.

    Everything I like is either illegal, immoral or fattening

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