To me that crank boss looks stuffed.
Not much better than a broken one.
The blade carrier has spun on it and it looks twisted. They are hard to straighten and reuse.
Engineering fail IMO.
If its had a bar blade on it always check the crank is not bent.
I have seen them where the ovals are worn off so 2 big coach head bolts have been fitted. Not a good idea with a bar blade. I dont see an issue with the 4 blade swing back disc. 2 blade it would be touch and go.
Go and buy a 3/8unf bolt about 3" long (actually buy a few and put some aside, and a 7/16unf as well). Drill a score in the centre of the top of the head. Screw that up the crank a fair way, put a spanner on it and leave it there. Use a 6 or 8 inch 2 leg puller, Nose into your little hole in the head of the bolt. Tighten the puller up, let the spanner come round and hit on a leg of the puller so as you wind the puller it does not just wind the bolt in and bottom it out. Put a bar though the puller to stop the crank spinning. It will be tight. Take care not to loose a finger or eye.
Ive never used heat.
The only one i have not got off so far to date was a big old Rover 20" cut boss. Had to split it with the grinder. Upon doing that i realise id done it the right way, no way it was coming off.
