A drill with a drill flute (12) includes symmetrical fluted lands (20) helically extend around a core, wherein grooves (18) remain between the fluted lands, said grooves having a width (72) that exceeds the spine thickness or width (24) of the fluted lands (20), and wherein the grooves (18) comprise a convex core reinforcement (22) at the groove bottom thereof. The width (24) of the fluted lands (20) at the drill head side end (16) is smaller than at the shank side end (14) of the drill helix (12), and at least increases in certain areas. The core reinforcement (22) at the drill head side end (16) is more convex than at the shank side end (14), thus has larger radii (40, 42).

The present invention relates to a drill bit structure which comprises a body. The body has a free end, an intermediate section and a connection end. The body comprises a first groove portion, a second groove portion, a third groove portion, a fourth groove portion and a fifth groove portion. The first groove portion is partially overlapped with the third groove portion from the free end. The second groove portion is partially overlapped with the fourth groove portion from the free end. After extending a preset axial distance from the free end, the first groove portion and the second groove portion are partially overlapped with each other by forming an intersecting protrusion. The fifth groove portion is extended from the intermediate section toward the connection end. The first, second, third and fourth groove portions are extended to the fifth groove portion.

A drill structure includes a shank part and a flute part. A chisel edge is formed on the front end of the flute part and two primary relief faces with tile directions toward the shank part are symmetrically formed on the two sides of the chisel edge. Each primary relief face has a cutting edge, a knife-back edge, and an outer edge. The outer edges are respectively helically extended around the periphery of the flute part to form two helical cutting edges and two helical grooves. Two assist relief faces are respectively formed on the inner walls of the two helical grooves, and every assist relief face is connected with the cutting edge of one primary relief face and portion of the knife-back edge of another primary relief face. The drill structure can decrease the thickness of the chisel edge, reduces the resistance during drilling, and increases the life.

A step drill includes a stepped cone formed with a tip and a bottom, a shank extending from the bottom, and steps formed between the tip and the bottom. The stepped cone includes a transitional portion formed on one of the steps. There is a first length between the transitional portion and the tip. There is a second length between the transitional portion and the bottom. The stepped cone includes four helical grooves. The first and second helical grooves are located opposite to each other. The third and fourth helical grooves are located to each other. The first and second helical grooves extend from the tip. The third and fourth helical grooves extend from the transitional portion to the bottom.

A drill bit includes a pointed head and a bit shaft. A dust suction passage is formed in the bit shaft. A hole with an opening is formed in the pointed head or in a portion of the bit shaft, the portion being near a distal end of the bit shaft. The bit shaft includes a first portion, the first portion including a core and a rib. The core extends in an axial direction, and is thinner than the pointed head. The rib protrudes radially outward from a side surface of the core, and extends over an entire length of the first portion. The dust suction passage extends through the core in the axial direction.

Provided is a body capable of suppressing the bending of the body during machining. A body includes: a first attachment part serving as a portion that is provided on a leading end side and has a cutting edge mounted thereon; and a second attachment part serving as a portion that is provided at a position different from a position of the first attachment part along a circumferential direction and has a guide pad attached thereto on the leading end side. One discharging groove that extends from the leading end side to a base end side and is used to guide and discharge a fluid to the base end side is formed on an outer peripheral surface of the body, and at least a part of the discharging groove is bent.

An annular hole cutter includes a cutter body having cutting teeth and a plurality of flutes extending from the cutting teeth around a side wall between a first and second end, with the flutes separated from each other by a land. The hole cutter includes side walls defining primary and secondary flutes with each one of the primary flutes defining first and second helix angles, and with each one of the secondary flutes defining a third helix angle and a fourth helix angle, with the second helix angle being greater than the first helix angle.