the adzing bit assembly includes a circular cutting bit with a circular edge formed by the merging of its flat face and its peripheral surface at an acute angle . a cutting bit shield abuts and covers the face of the cutting bit and extends to a diameter substantially equal to the diameter of the cutting edge , so as to shield the face and the cutting edge of the cutting bit . the cutting bit is fabricated from harder material than the cutting bit shield , so that the cutting bit shield wears away during use and the circular cutting edge of the cutting bit is progressively exposed .