| 摘要 |
A seismic tool assembly for effecting a drill hole and enlarging a lowermost end thereof whereby an anchor can be set more securely therein. A drill bit is inserted through an opening in a stabilizer, which is positioned over a surface where the drill hole is to be made. The bit is placed into the drill hole, attaining a position at the lowermost end thereof. The lower end of the bit has a cutting portion having a cutting radius greater than that of the bit body whereby, when the bit is inserted fully into a lowermost end of the hole and rotated, the cutting portion enlarges the lowermost end of the hole, whereby flanged portions of an anchor will rest within the enlarged area, retaining the anchor in place. The stabilizer has a flanged portion extending into the hole, which provides a space between the bit and the stabilizer to permit limited tilting movement of the bit during drilling to enlarge a lowermost end of the hole, and for aiding in accurately inserting the bit into position.
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