On a serious note,
instead of trying to repair a broken crankshaft by welding at the spot where it cracked,
wouldn’t it be better to select two spots on either side of the crack
and precisely cut out the bad section,
and use a jig to hold in a replacement section during welding, tempering, and stress relief?

The two spots where welds should be selected to minimize “stress concentration geometry” like corners, notches, etc.

I once ordered machinists to try to hand polish the journal of a 60 year old Alco Locomotive Diesel crankshaft.
The crankshaft was not broken or cracked, just needed to be reduced so an undersixed bearing could be used.
It took several days of hand work, but in the end everything mic’ed OK.
The engine then ran smoothly, without any odd vibration or noise.

But... within a year the crankshaft suddenly broke at that journal without giving any sign of trouble.



I will not say that amazingly precise work cannot be done with primitive tools in poor foreign countries.
If you have never seen what comes out of the workshops of Darra Adam Khel it is amazing.....

https://en.wikipedia.org/wiki/Darra_Adam_Khel