Patent ID: 8403600

Claim:
A drilling tool comprising first and second ends, a shaft extending between the ends, the first end having a drill bit to penetrate rock, the drill bit and the shaft having complementary threads, and a stop that limits rotation of the drill bit on the shaft to maintain the drill bit in loose threaded connection with the shaft during drilling in a first direction, wherein the stop comprises cooperating abutment surfaces, one said surface disposed on the drill bit and the other said surface disposed on the shaft, wherein one of the drill bit and the shaft is provided with a projection and the other one of the drill bit and the shaft with a recess, said projection and said recess having respective ones of said abutment surfaces that provide said stop, and wherein the stop limits the drill bit from rotating on the shaft so as to maintain a gap between an end surface of the shaft and an end surface of the drill bit during drilling.