Step drill bit

The utility model provides a drill bit which comprises a handle portion and a main body, the handle portion extends along the axis of the drill bit, and the main body is provided with a near end closeto the handle portion and a far end opposite to the near end. The body defines a plurality of axially stacked, progressively sized steps including a first step at a distal end and a terminal step atthe proximal end. The drill bit also includes a flute located in the body. The flute defines an elongated groove extending from a distal end to a proximal end. The drill bit also includes a pluralityof cutting edges formed in the body. Each cutting edge is disposed along one of the plurality of steps and defines a helix angle and a rake angle. And the helical angle of the cutting edge at the terminal step is larger than that of the cutting edge at the first step. The ratio of the helical angle to the rake angle of the cutting edge at the first step is in the range of 0.5 to 2.4, and the ratioof the helical angle to the