My neighbour has a drum mower with two broken blade disc drive gears.
The shaft holding the rotating blade plate had a fatigue crack that ended up breaking the shaft into two pieces.
I do a simple repair for this component by tapping a M14/1 thread to the gear and then making a stud bolt to replace the broken off part.

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In this video I am using:
- Weiler Matador SV (1972) Lathe
- Schaublin SV-51 (1955) Milling machine