| 摘要 |
A protective collar for a boring bit which interfaces with a boring head whereby shear forces developed during a boring operation are transmitted through the collar to the boring head, with minimal shear force being carried by mounting bolts. A collar is connected to a boring bit, wherein a head receptacle formed by the collar seatably receives a boring head with substantially close clearance so that shear forces during boring operations are transmitted from, the boring bit to the boring head through the collar. The preferred collar is fabricated from a pipe section, such as for example steel seamless pipe. In one embodiment, a bit recess is cut for interfacing with a boring bit at the head face connection thereof. A head recess is cut opposite the bit recess for providing an exit for the water spray from the nozzle thereof. In another embodiment, the collar has an inclined face with bores alignable with the bores in the boring head when the head is mounted within a receptacle in the collar. The boring bit is mountable on an inner interface surface with the bores in alignment for receiving threaded fasteners. In another embodiment, an opening is formed in the collar for receiving one end of the boring bit. When seated in the opening, the boring bit is engageable with the connection face of the head for receiving fasteners through a flange on the collar overlaying the end of the boring bit and the boring head.
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