When I was using the KA for grinding and heavy bread making, I
stripped the plastic gear in the head several times. Getting the
trim ring off without damage was the biggest challenge, and getting
the lower head to come out of the mating recess (after removal of
restraining screws) was almost a much a challenge. Patience and
care did cause success.
The gear is held in place with a steel pin that needs to be tapped
out with a pin punch. Reassembly is very fast.
The plastic gear is designed to fail - and keeps other parts from
breaking first. It is like a fuse in an electrical circuit.
Have not had to replace one since the kids left home -- and I cut
down on bread making after bypass surgery.
Ken in Juneau