| 摘要 |
A drill is disclosed. The drill of the present invention includes a body (2), which has a twisted shape and forms a hole in a piece of metal using rotation, and a shank (3), which is integrated with one end of the body. The shank is coupled to a chuck of a drilling machine to receive rotating force from the drilling machine. The shank comprises three rounded portions (5) and three linear portions (4), which are alternately formed around the shank in a predetermined range from the end of the shank towards the body, thus having a triangular cross-sectional shape. Therefore, the drill of the present invention can prevent the shank from slipping with respect to the chuck even when the drill is rotated at a relatively high speed, thus increasing processing accuracy and increasing the lifetime of the drill and the chuck. |
