Abstract: A remanufacturing method of a drill includes providing a drill with a worn-out area. The drill comprises: a shank part; and a flute part arranged on one end of the shank part. A chisel edge is formed on the front end of the flute part, and the radius of any one of the cross section of the chisel edge is defined as a core thickness; a first blade and a second blade with tilt directions toward the shank part are formed on the two sides of the chisel edge. The first circumferential surface of the first blade and the second circumferential surface of the second blade are respectively extended and spiraled toward the shank part along a periphery of the flute part and form two helical cutting edges, a first debris-discharging groove and a second debris-discharging groove. The first blade comprises a first cutting edge. The first cutting edge and the first circumferential surface define the worn-out area.

Abstract: A drill structure comprises a shank part and a bit part. A web is formed on the front end of the bit part. Two sides of the web are tilted backward to form two cutting faces. At least one chip-discharge groove is formed on the surface of the bit part. Each cutting face includes a primary cutting face and a secondary cutting face. The thickness of the prismatic web edge of at least one primary cutting face is smaller than the outer-side width of the primary cutting face. An auxiliary cutting face is extended to the wall of the flute from the cutting edge of the primary cutting face and a portion of a blade back of the secondary cutting face of another cutting face. The present invention decreases the drilling resistance during drilling a hole and increases the service life of the drill bit.

Abstract: A drill structure includes a shank part and a flute part arranged on one end of the shank part. A chisel edge is formed on the front end of the flute part and two drill blades with tilt directions toward the shank part are symmetrically formed on the two sides of the chisel edge. Every drill blade includes: a primary relief surface with a cutting edge, a first connecting edge and a first chamfering edge, a secondary relief surface with a knife-back edge, a second connecting edge, a second chamfering edge and an outer edge, and an assist relief surface. The second connecting edge joins to the first connecting edge, and the second chamfering edge connects with the first chamfering edge. The assist relief surface, which tilts toward the shank part the, is extend from the first chamfering edge and the second chamfering edge. This drill structure can improve the surface finish of the drilling hole.

Abstract: 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.