Gearbox Housing Bearing Bore Rebuild

The challenge

A gearbox bearing bore spun in service and wore oversize, so the bearing outer race no longer seated tight in the housing. Once the bore opens up, the bearing creeps and turns in the bore instead of holding fast, and that wears more metal away while the shaft runs out of alignment. Left that way, the gearbox runs hot, loses the bearing, and risks taking the shaft and gears with it. The plant needed the bore back to the correct dimension, but the cast housing was not something they could quickly replace and there was no spare on the shelf.

Our approach

We take the housing into the shop and clean the bore back to sound metal so we can see how far the wear has gone. We rebuild the worn bore cold with Belzona 1000 Series composites, building up enough material to take the bearing again. Then we use a release agent on a mandrel sized to the bearing and form the composite against it, so the bore is reformed back to the correct dimension as it cures. Working cold means the cast housing sees no heat and no distortion, and we never have to set up a machine to bore a new seat.

1. Assess and measureWe inspect the spun bore, measure how far it has worn oversize, and confirm the bearing dimension the bore has to return to.
2. Surface preparationWe clean the worn bore back to sound metal and roughen the surface so the composite bonds to the housing.
3. Cold rebuild the boreWe build the worn bore back up with Belzona 1000 Series composites, working cold so the cast housing sees no heat or distortion.
4. Reform to dimensionWe apply a release agent to a mandrel sized to the bearing and form the composite against it so the bore cures back to the correct dimension.
5. Cure and return to serviceWe confirm the cured bore is on size, then hand the gearbox back so the bearing seats and the shaft runs in alignment.