I bought a keen kutter KK19 block plane at the local tool club for all of $2 last weekend. It had a cracked cheek and missing knob, but I wanted to try mig welding it back together so I gave it a shot today. I'm a pretty bad welder, but it was a fun experiment.
Original plane with crack:
Removing material to make room for the weld bead:
After a lot of cleanup, and after restoring the other parts:
Another view:
It works decently, but the iron required a steep back bevel to get to good steel and the high carbon piece is almost used up. I might replace it someday if I can find something that will fit (anyone know of a commercial option that will work?):