Just thinking out loud

I second the EDM. When I was fixing sleds and any small motor stuff I used EDM regularly to burn out bolts. I had a key way break on a kart racing engine and had the crank welded and burned a new key way with EDM, worked perfect. Other option is to use a center drill from a lathe or mill they are very hard and won't move even when drilling on an angle like your broken bolts. Just make sure everything is clamped down super tight.

Had the joy of plowing all day when everything just goes perfect. 😂. NOT! I’ve got a plasma cutter and tig/mig welder. My favorite shop must along with welt band saw. I put the 48/40 on for a quick fix and pulled it over 3 times and the fken pull cord broke. Just the way chit goes. Rewound with new rope and pulled over twice and didn’t retract. The way it goes… Tks for all the input.

anybody mention welding.

Weld a nut on the broken bolt?

Thinking about this for a bit, I’ll have to agree.

yep, it does at least two things, first it gives you something you can put a wrench on and secondly it thermally shocks the broken( most likely corroded) and stuck bolt . Works great but I've never done anything as small as a helix.

Anyone ever weld out a pressed in bearing race?

run a tig arc around the race and it should fall out,,thats how I take out valve seats.

Good to know these things!!!