O-ring ends "oh, darn!" when changing bits
Slide a rubber O-ring onto the router-bit shank, as shown above, before you insert it into the collet. (You'll find 1⁄4 " and 1⁄2 " inside-diameter O-rings in the plumbing aisle.) Position the bit at the height you want, and slide the O-ring down to the collet face. Now, you can tighten the collet nut while the O-ring holds the bit in place for you.
—William Sand, Morristown, Minn.