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I cannot get my pinion/worm gear off the axle

Many questions arise when pinions are to be moved from one motor to another, or when adding a new pinion. Gears are usually press fit from the factory, not glued. Here are a few guidelines;

  • Use a gear puller with care when removing pinions. A common error is to use force when the axle protrudes trough the pinion. The puller will then slip and break. Start with a larger bolt in the puller in such cases.
  • Various other methods can be used to remove the gear, but be prepared to scrap the old motor
  • Using a torch to heat the gear will widen it, and can ease the removal.
  • Using heat can also loosen glue.
  • Examine the removed gear and adjust the worm with a needle file, then polish with emery paper.
  • If the fit is tight when you want to insert a new gear, put the motor in the freezer for an hour, and heat the pinion with a torch. Plan carefully as you only have a few thenths of a second to put the pinion in place
  • If the fit is loose, use blue Loctite or similar to fasten it, as this is reversible
  • For the Bachmann 0-4-0, NWSL Steel Worm 0.4MOD x 6mm x 1.5mm bore #50400-6 can be used as a replacement. It is 1mm larger than the original, so be prepared for some shimming of the motor.
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