1/2" worm gear shaft repair help

This shaft is buggered, including missing about an inch in length. It's stainless (dunno what type; marine service intended.) It's a crank for a mechanism to raise/lower something that weighs about 60 pounds, so it does not see enormous torque. Shaft is 1/2" diameter, about 4" long. In second pic you can see the gearbox to give context.

I was thinking cut off shaft, bore 1/2" hole through worm, and locktite new shaft in place. Is that the right/best approach, or something else.

Suffice to say, buying a new part is not an option.

Yes, that's the way to go but you need to broach a 1/8" keyway in it. Use locktite too if you want but the keyway should be there. Peter

What caused it to fail? I would simply weld an oversize chunk of like material onto the shaft, and machine it straight. You can pick where you want the weld zone to be, probably a little ways away from the high stress point (where it emerges from a bushing or bearing).

I'm with Hu.

Failure was unrelated to use. The whole assembly was abused, dropped maybe, and the shaft badly bent where it emerged from the housing. The end you see is what's leftover from my removal technique. It was bent enough that the bronze bushing it runs in was mangled, so that even after cutting shaft off flush with bushing, the shaft was still bent into the bushing and could not turn. So I drilled the bent part out.

Maybe this is a question for loctite literature, but I wonder about figuring its strength. I was reading a thread yesterday in which someone was saying they could not budge a loctited bolt with an 18" wrench. That was somewhat larger diameter, and a threaded part, so much more surface engagement, but is loctite alone ever suitable for something like this?

I don't have broaching equipment, so I was hoping to avoid keying.

mark thomas said:

I don't have broaching equipment, so I was hoping to avoid keying.

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Scotch key. Bore out the worm, fit a new shaft with Loctite to stop it moving then drill a hole with 50% overlap in the shaft/worm body, tap and screw in a grub screw. If you're really paranoid about it moving, put in 2 screws 90 deg apart around the circumference.

Problem solved and it can still be taken apart if you ever need to.

PDW

PDW, thanks, I forgot about scotch keys. Seen them mentioned here before, but never done it. Seems like a great solution.

This thing really doesn't get much torque, ~20 ft lbs I would guess. The original crank was only about 6" long. It was engineered for extreme durability (navy use.)