Blade Runout

Runout is wobble in a spinning blade, bit, or arbor -- the cutting edge tracing a slightly wider circle than it should because the arbor, collet, or blade itself isn't running perfectly true. Even a small amount, a few thousandths of an inch, shows up as a rougher cut surface, inconsistent joint fit, and faster-than-normal bit or blade wear, since the cutting edges are taking uneven bites instead of a clean, consistent one.

Runout is a machine and setup problem, not a technique problem -- caused by a bent arbor, debris trapped between a blade and its washers, a worn collet, or a blade that isn't seated flat. Checking for it (a dial indicator against the blade or bit, or simply watching closely at low speed) is worth doing when cut quality degrades for no obvious technique-related reason.