| 摘要 |
A drill bit for drilling a hole of a selected diameter in a wood workpiece includes a conically shaped tip having a main cutting portion and a thread series operable to threadingly draw the drill bit into the wood workpiece. The thread series has a diameter which progressively increases in a direction opposite to the drilling penetration direction of movement of the drill bit to a maximum diameter which is the same as the selected diameter of the hole to be drilled. The drill bit also includes a cylindrical portion extending from the conically shaped tip, a spiral screw shaped splinter groove for conducting splinters in the drilled hole away from the drill bit penetration area and a centering drill portion with a self cutting thread series.
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