| 摘要 |
For removing damaged screws, a bit having an axis and a tip end formed with a point and a rear end formed in hexagonal cross-section adapted for installation in a chuck of a variable speed reversible drill, the tip having a plurality of longitudinal recesses uniformly disposed about the tip end, each bordered by a scraping surface facing in a counter-clockwise direction, the scraping surface formed with a distal straight scraping edge, the scraping edges of the recesses each being disposed at a scraping edge acute angle to the axis less than about 70 DEG , and a support portion behind each scraping edge, the support portions each defined by a relief surface curving away from the scraping edge down to a rearward edge bordering one of the longitudinal recesses, being disposed at a more acute angle to the axis than the scraping edge acute angle. <IMAGE> |
