Patent ID: 6543971
Filing Date: 2003-04-08
Classification: B23B,Y10T

Abstract:
A clutch mechanism for limiting the depth of penetration by a drill, said clutch mechanism comprisinga) an arbor having a first end insertable within a spindle of a machine tool and a second hollow end, a first plurality of apertures formed in said second hollow end adjacent a terminal end thereof, a second like plurality of locking balls received in and protruding partially out of said first plurality of apertures; b) a collet holder having a first end partially received within said hollow end of said arbor engaging said locking balls and restraining them against collapsing inwardly within said apertures, a central portion having drive surfaces thereon, and a second end receiving and securing a drill bit therein, said arbor, said collet holder and the drill bit forming an inner assembly; c) a ball locking ring surrounding a portion of said second hollow end and said first end of said collet holder, said ball locking ring having a first section with a first inner diameter engaging said locking balls and holding them in a first position in contact with said drive surfaces of said collet holder and a second section with a second larger inner diameter maintaining said locking balls in said apertures but permitting said locking balls to move to a second position disengaged from said drive surfaces of said collet holder; d) means for mounting said ball locking ring on said second hollow end of said collet holder, said means for mounting permitting relative longitudinal movement therebetween; e) a nose cone assembly including a nose cone surrounding a portion of said second end of said collet holder and at least a portion of the drill bit; f) means attaching said nose cone assembly to said ball locking ring such that the nose cone assembly and ball locking ring move longitudinally as an outer unit; whereby, when said distal end of said nose cone contacts a workpiece being drilled, forward movement of said outer unit is halted and relative longitudinal movement of said inner assembly over a short distance permits said locking balls to move from said first diameter of said ball locking ring to said second diameter disengaging rotational drive of said collet holder and drill bit thereby limiting the depth of penetration of the drill bit.