re: Stupid question of the week

If the router is not designed for a fully-seated bit, the bit will seat against the shaft before the collet split-nut tries to squeeze it down (my understanding is that the collect pulls the bit in abit, as it closes around it). What results is that the collet is pulling bit against a steel shaft – this is the limit of my knowledge.

I’ve been using Sommerfeld’s rubber grommets in my routers for years – these rest on the motor-shaft end, and have the effect of prohibiting the metal-to-metal contact (there are other benefits, as well). As such, in my routers, I always have pliable rubber between my fully-seated bit and the motor shaft.
MJCD