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I finally got sufficiently annoyed by my bench grinder's violent vibrations. I took off the discs and discovered that the little discless stubs are already wiggling themselves quite substantially. First problem to solve is (probably?) to make the arbor straight.

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However it seems like a pretty solid piece of steel. Do you have any experience with straightening such a machine part?

The first thing that comes to my mind is to grip the arbor in a vise and either slam it with a rubber-wrapped hammer or stick a pipe over one end to just the right depth and push on it. Taking an unbiased look at my machinery repair record, this is likely to make things worse. Since I will probably need to balance the discs eventually, would it make sense to let the arbor as it is and compensate by balancing the discs in a slightly crooked way?

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    Not really a home improvement question...
    – keshlam
    Sep 4, 2023 at 14:00
  • @keshlam Please, could you advise a more suitable SE site? Engineering perhaps? Sep 4, 2023 at 14:30
  • Is it the arbor not being straight or something else? Has been this way since new? Are the bearings on tight and spin easy? Are the bearings tight in the housing?
    – crip659
    Sep 4, 2023 at 14:30

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A frame challenge: At the spin speeds of this arbor, straightening it by hand will probably not be sufficiently possible. It probably needs to have been machined to tolerance and balanced by sufficiently-accurate jigs and testing to have been smoothly spinning at first.

Attempting to modify the mounting of the discs may be a safety issue, and the altered mount may not hold the disc sufficiently: it could do a rapid unplanned disassembly and shrapnel conversion.

Buying a new arbor (or a new grinder) may be the only solution that results in good smooth spinning. And of course if the disassembled grinder was new it may have been a manufacturing defect and a replacement could be had, if removing the arbor did not void the warranty.

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The wisest and best thing you can do is buy a new grinder.

You will never get the arbor straight by pounding on it. Perhaps it can be machined straight. The cost of machining is probably more that a new unit. Then the arbor will be sized under specifications and possibly dangerous.

Just buy a new grinder.

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Shaft straightening is generally done with a press or jack, commonly hydraulic these days.

It requires considerable precision measurement capacity (need to find the point of deviation, and then press it just far enough past straight that it rebounds to straight) and is only a home project for people with a fairly advanced home shop.

"Hammer on it" works better in fiction than real life.

Replace, and don't abuse the next one so it doesn't get bent.

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