| 摘要 |
An auger is provided with a boring head having an arrangement for cutting relatively hard earth formations such as rock. First and second groups of drill bits are mounted to the boring head such that when the head is rotated, each bit in those groups cuts a different path at a different height to provide more than 100% coverage of the work surface being cut, while stabilizing the auger by distributing the down force of the auger over the entire work surface. The drill bits also are orientated to ensure bit rotation at relatively large attack angles (the angle the bit forms with the work surface therebeneath) of about 50 DEG -60 DEG to enhance auger penetration rates without detracting from the bit sharpening effect that results from proper bit rotation.
|
