[rotorwrench]

What one person may consider OK another won't. Some parts can have a fair amount of normal wear and be OK and others can cause stuff like slipping out of gear and the like. Very small pits largely due to light surface corrosion would be considered OK by most folks. Deeper pitting can cause fractures and tooth breakage under use. Large pits or gear teeth with a piece broken off are getting a bit beyond serviceability but some folks will run stuff until is completely fails. The problem can be that other parts may be damaged when a breakage occurs which will render even more parts unserviceable. I stop at light wear and surface corrosion myself. I'm too old and lazy to want to lick that calf over again.