| 摘要 |
<p>An embodiment of a spade bit (100) has straight grooves (128) at a lead angle (α) of 4 to 8 degrees placed on flat edges of the spade bit. In an alternative embodiment, a spade bit (200) has two steps (232a,232b) of straight grooves (228) at a lead angle (α) of 4 to 8 degrees placed on flat edges of the spade bit. In other alternative embodiments, a spade bit (300) has tapered flat edge which have straight grooves (328) at a lead angle (α) of 4 to 8 degrees placed thereon. The straight grooves on the flat edges of the spade bit allows the spade bit to pull itself through the workpiece with a minimal amount of penetration. The flat edges of the spade bit may also have cutting surfaces for cleaning the hole and permitting the easy removal of the spade bit from the hole after drilling.
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