Collet chuck

Claim 1

A collet chuck comprising a chuck body having a conical bore axially formed therein, a collet being longitudinally split and having a conical surface complementary to the conical bore of said chuck body, said collet being received in said conical bore and adapted to be contracted upon axial movement in said bore, a lock nut rotatably mounted on the chuck body, a nose ring rotatably connected to said lock nut and being circumferentially engagable wiTh an end portion of said collet, said nose ring and said end portion of said collet having means for contracting said portion of the collet upon axial movement of the nose ring, a first helical groove formed in the inner periphery of said lock nut, a second helical groove formed around said chuck body correspondingly to said first helical groove, said first and second helical grooves forming a helical channel between the lock nut and the chuck body, a plurality of balls received in said helical channel and being in rolling contact therewith to permit the axial movement of said lock nut upon rotation of the lock nut, first and second stops projecting respectively in said first and second helical grooves so as to prevent removal of said balls out of said helical channel, said stops being spaced apart a sufficient distance to allow the balls therebetween to rotate relative to one another for reducing friction between the channel and the balls received between the stops to facilitate rotation of said lock nut, and means for holding some of said balls in said helical channel in tight frictional contact with one another to provide friction between the channel and said some of the balls to prevent the lock nut from becoming loose with respect to the chuck body when a tool has been gripped by said collet.