I'm repairing a Honda HRM215 self-propelled lawn mower and the transmission has a broken beveled gear. By the way, minor gloat here - neighbor down the street was moving and decided to discard the mower. She told me it needed a new crankshaft and spewed oil like a Texas gusher. Her mechanic told her the repair was more than the mower was worth. The full retail price on these things is about $800. I figured it would be fun to take it apart. A lot of head scratching (figuring out what all is where) and a can of carburator cleaner and the engine runs OK (still idles roughly). No oil gushes or damaged crank.
The gear appears to be sintered steel or iron (just a guess). It is magnetic and the break appears to be "grainey". The outside appears to be coated because it is smooth and "greenish gold" in color. I see very little wear on the gear, mostly just a polishing or burnishing of the contact surfaces.
The shaft appears to be stainless steel (not magentic). The gear needs to be fixed to the shaft. The original assembly mushroomed the shaft to lock the gear in place (much like a rivet). The shaft has some blue and straw color spots where the gear sits.
If (or when) I get the gear fixed, the mower should be fully functional again.
I can carve a gear out of some scrap steel, but this is way over my head. I would like to reserve this as a last option. I've never cut a gear before and I don't have an indexer - but I am pretty good with a dremel.
I can braze the gear back together and to the shaft. I have two kinds of braze, one is hard silver solder from some silversmithing experiments, the other is the braze sold for joining bandsaw blades. I'm not sure which braze would be more appropriate for the task here. I figure I can rough up the surfaces with a dremel and clamp the gear together on the shaft with plenty of flux, heat it with a propane torch and let the braze wick into the joint.
I'm not sure about the durability of a brazed joint in a situation like this. Any guidance from the collective?