Here's the damaged hub and sheave half as I received it from Todd. You can see where the key failed and ate up the bore of the sheave half. The hub is obviously destroyed and was cut off the motor shaft:
The broached keyway in the sheave half was rather augered out. I decided to proceed with a brazed repair. I could have just broached another keyway, but that would increase the possibility of the nylon bushing failing prematurely.
The sheave half is cast iron. So, to begin I preheated the casting to over 1,000F with a large propane torch, otherwise known as a "weed burner":
Preheating the part reduces the temperature gradient between the brazing zone and the rest of the part. By reducing the temperature gradient the internal stresses are reduced and thus the risk of cracking.
Copying my 1-1/2" broach guide bushing, I made a 1-5/8" guide bushing from 4140PH:
Here's the part after brazing while it was cooling under flame back to black heat:
Once back below 1,000F the sheave half was covered with fiberglass insulating blankets and allowed to cool to room temperature over about 5 hours.
Here it is after sandblasting, ready for machining:
The sheave half was bored out to clean up and the bushing groove cut back in. Then I cleaned up the face of the sheave half. It was worn slightly, as this photo shows:
After a second cut the face cleaned up. I also faced the stationary sheave half the same way:
I then broached the keyway in the same place as it was originally, using my new guide bushing:
Here's the movable sheave half, ready for a new plastic bushing:
Before I can size the bushing I need to make a new hub. To start, I've drilled a hole and reamed it to fit the 1/2" motor shaft. This reamer runs about .0012" over 1/2 which is perfect:
After reaming the motor bore, the stock is pulled out of the chuck a ways, indicated for bends which would affect the alignment of the motor bore and the OD of the hub is turned:
To be continued...
