I want to weld a halfmoon key into my tablesaw blade arbor in an attempt to save the tablesaw rather than trashing it and buying a new one. I am looking for advice on this.
I have 2 and have constantly fought with these. I put a new motor on one and had to tweak the belt placement. I think that come spring (that one is in the garage) I will use loctite 300 on it to hold the set screws and that one should be good. The one with the waffeled 1/2 moon keyway in the blade arbor is the one that needs the work. The pullys are lined up correctly. It was waffeled a bit when I got it and has gotten worse over the years. Now it is to a point of weld it or get rid of it.
Any advice? I assume i will have to remove the top, then weld the key in making sure to have it in the absolute correct position when doing so-Any advice on how to make that happen?? I was thinking some loctite 300 at the base, set it up for a week then weld. I can file down burs for a tight fit-it wont be fun in that tight space but possible. I figure 4 spots, 1 on either end then 2 lines to fill cavitys on either side. Wait a long while to cool in between.
No i have no experience with welding, i will be hiring this done.
Any advice?!?

 

Are you talking about one or two saws? It sounds like you are jumping back and forth describing two machines.

If you want to glue a woodruff key into a shaft or collet I would braze it. They might be able to clean everything. Then use brazing paste or a tiny bit of filler in the bottom of the cavity. Then set the key on top and heat everything. This hopefully will avoid the filler creating a fillet around the key. If you weld it I would TIG only the very ends of the key. It won't be terribly strong but it reduces the chance of buggering things so things can still go back together.

 

Since you are going to have someone do the work, another option is to machine the shaft for a slightly larger key, then your back to a proper fit.

 

I agree, it is going to be MUCH easier to get a precision fit by removing a bit of steel with a slightly larger woodruff cutter and enlarging the slot; as compared to trying to accurately weld or braze in a new key.

I'm curious, since the OP "had to tweak the belt placement" and keys are often used as shear points so the mechanism fails safely, what is causing the "waffling"? If the keyway is being deformed, I'd double check the belt ratios and bearings.