Abstract

A drill chuck for use with a tool having a shaft has a chuck body centered on and rotatable about an axis and an adjustment body centered on the axis, rotatable about the axis on the chuck body, and axially fixed on the chuck body. One of the bodies is formed with a plurality of angularly equispaced jaw-guide passages centered on respective jaw axes all lying on the surface of an imaginary cone centered on the axis. The other of the bodies is formed with a screwthread centered on the axis and exposed in the guide passages. Respective jaws displaceable in the passages along the respective axes are each formed with a row of teeth meshing with the screwthread so that relative rotation of the bodies in one direction moves the jaws radially inward and axially forward and opposite relative rotation moves the jaws radially outward and axially backward. Each of the jaws is formed with a generally axially extending entrainment ridge projecting radially inward relative to the chuck axis from the respective jaw, lying offset forward in a normal rotation direction of the chuck when drilling from a respective jaw plane including the respective passage axis and the chuck axis, and lying mainly within an imaginary cone defined by the jaw axes and centered on the chuck axis.