The unwanted radial movement of a rotating tool, usually a drill bit, as it begins to cut into a surface. When a tool deflects instead of biting straight in, it creates an off-center or angled hole. Machinists prevent this by using rigid setups, starting holes with a center drill, or keeping the tool stick-out short.
Heard on the job
Use a spot drill first, or that long jobber bit is going to walk all over the curved face of the casting.
Insider tip
A dull drill bit is practically guaranteed to wander off center, especially on hardened materials or angled surfaces.