[EricH]

Originally Posted by pilleya

It only really takes one tooth to break or chip to cause all the teeth to be stripped off the gear, as I believe that the shrapnel causes the next tooth to be clogged and break.

Not quite...

What usually happens is that if one tooth breaks off, the next tooth takes more force than it would ordinarily (fewer points of the same force being applied = more stress as well), plus a chance of shock loading. Then that one takes off... repeat until you're out of gear teeth.