Drill chuck

A drill chuck for use with a tool having a shaft, the chuck comprising:

• a chuck body centered on and rotatable about a chuck axis;
• an adjustment body centered on the chuck axis, rotatable about the chuck axis on the chuck body, and axially fixed on the chuck body, one of the bodies being 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 chuck axis, the other of the bodies being formed with a screwthread centered on the chuck axis and exposed in the guide passages;
• and
• respective jaws displaceable in the passages along the respective jaw axes and each formed with
• a row of teeth meshing with the screwthread, whereby 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,
• a generally axially extending first entrainment ridge projecting radially inward relative to the chuck axis from the respective jaw, lying offset forward, relative to a normal rotation direction of the chuck when drilling, from a respective jaw plane including the respective jaw axis and the chuck axis, and lying mainly within the imaginary cone, and with
• a second such entrainment ridge offset from the respective first ridge and lying relative to the normal rotation direction behind the respective first ridge, each second ridge being offset radially of the respective jaw axis inward with respect to the respective first ridge from a respective plane perpendicular to the respective jaw plane.