A chuck assembly for a rotary power tool includes a chuck body rotatable about a central axis. The chuck body has a plurality of slots, each oriented at an oblique angle relative to the central axis. The chuck assembly also includes a plurality of jaws, each movable along a respective one of the slots. The chuck assembly also includes a collar coupled to the plurality of jaws. The collar is selectively engageable with the chuck body such that, when engaged, the plurality of jaws are movable along the plurality of slots in response to rotation of the collar.

A chuck for clamping a shaft. The chuck includes a jaw guide defining an axis and including jaw channels circumferentially distributed about the axis. Interleaving jaws are slidably disposed in the jaw channels and each jaw has a clamping surface facing the axis and a driving surface opposite the clamping surface and a protrusion on one side and a cavity on another side with the protrusion of each jaw disposed at least partially in the cavity of an adjacent jaw. A spring having a base and fingers extending from the base are engageable with the jaws to retain the jaws in the jaw channels. An inclined engagement surface is included on an inner surface of the jaw guide or an engagement sleeve. Displacement of the jaws relative to the inclined engagement surface in a clamping direction displaces the clamping surfaces toward the axis.