| 摘要 |
The invention provides a bit (10) for use with a rotatable tool, said bit including: a shaft (12) having a rearward end adapted to be held by a chuck of the rotatable tool, and a forward end (18) having cutting tips formed thereon; a reaming head (14) including a body having a bore (16) adapted to receive the shaft therethrough in a sliding fit, the body having a plurality of cutting blades (26) formed on at least one peripheral surface thereof; the bore and/or the shaft having formations thereon such that when the rearing head has the shaft operatively located in the bore the reaming head is rotationally locked into the shaft; the reaming head and the shaft being separable from each other to allow either component to be replaced independently of the other. The invention also provides a bit having a tip end and shank end for use with a rotatable tool, said bit having at least 4 blades (24) to engage ard drive a screw when said rotatable tool is rotated, each blade including at said tip end a bevel so as to form a cutter (22) at the extremity of said blade, each bevel and/or cutter being able to cut in the same rotational direction. The invention further provides a method of making a bit for use as a screwdriver and countersinker, said method including the steps of: 1) forming at least a four blade screw driving end onto one end of blank, 2) forming a bevel at the extremity of each blade, said bevel producing an inclined plane cutter.
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