Provided is a method for manufacturing a sintered component, which can suppress occurrence of edge chipping when a through-hole is formed in a powder-compact green body and also has a good productivity. The method for manufacturing a sintered component includes a molding step of press-molding a raw material powder containing a metal powder and thus fabricating a powder-compact green body; a drilling step of forming a hole in the powder-compact green body using a drill; a sintering step of sintering the powder-compact green body after drilling, wherein the drill used for drilling has a circular-arc shaped cutting edge on a point portion thereof.

According to one implementation, a drill includes the first cutting edges, the second cutting edges and a deflection reducer. The first cutting edges drill a prepared hole to a workpiece. The first cutting edges are formed in a tip side of the drill. The first point angle and each first relief angle of the first cutting edges continuously or intermittently decrease from the tip side toward a rear end side of the drill. The second cutting edges finish the prepared hole. The second cutting edges are formed at positions away in the rear end side from the first cutting edges. The second cutting edges have the second relief angles at a maximum diameter position. The deflection reducer reduces deflection of the second cutting edges. The deflection reducer is formed between the first cutting edges and the second cutting edges. The deflection reducer is inserted into the prepared hole.

A twist drill and an exchangeable head for a twist drill, the twist drill extending along a central axis of rotation and having a front end formed as a drill point with two cutting edges and at least two clearance surfaces. Two helical chip flutes conduct chips away from the cutting edges. Each cutting edge extends in a transition between the clearance surfaces. One of the chip flutes extends from an inner position adjacent to the central axis to a peripheral envelope surface and has a main portion closest to the peripheral envelope surface. Each chip flute is delimited by a side surface including a main rake face, which extends rearward from the main portion of the cutting edge. The cutting edges are contained in an imaginary conical surface, such that the twist drill is operable to generate a bottom profile having the shape of an inverted cone.

A step drill and a manufacturing method for a step drill in which cutting performance of a cutting edge of a step portion can be enhanced are provided. A groove includes a first ground portion forming an area embracing a second cutting edge of the step portion and a second ground portion forming an area on the heel side of the step portion relative to the first ground portion. Therefore, a convex blade part can be formed on a first cutting edge by performing grinding with the first ground portion and the second ground portion intersecting with each other. That is, it is possible to form the second cutting edge into a desired shape during grinding of the first ground portion. Therefore, cutting performance of the second cutting edge can be enhanced.

A three-flute drill includes a body, discharge grooves, cutting edges, thinning edges and gash portions. The discharge grooves are provided in an outer peripheral surface of the body. The cutting edges are provided on ridge sections between inner faces of the discharge grooves and flanks of the body. The thinning edge extends from an end of the cutting edge toward a radially inner side. The gash portion includes an R portion and a straight portion. A first ridge line between the R portion and the flank extends while curving toward a rotation direction, from an end of the thinning edge toward a radially outer side. A second ridge line between the straight portion and the flank extends linearly from an end of the first ridge line toward the radially outer side, and connects to the discharge groove further to the radially inner side than the outer peripheral surface.

A step drill and a manufacturing method for a step drill in which cutting performance of a cutting edge of a step portion can be enhanced are provided. A groove includes a first ground portion forming an area embracing a second cutting edge of the step portion and a second ground portion forming an area on the heel side of the step portion relative to the first ground portion. Therefore, a convex blade part can be formed on a first cutting edge by performing grinding with the first ground portion and the second ground portion intersecting with each other. That is, it is possible to form the second cutting edge into a desired shape during grinding of the first ground portion. Therefore, cutting performance of the second cutting edge can be enhanced.

According to one implementation, a drill includes the first cutting edges, the second cutting edges and a deflection reducer. The first cutting edges drill a prepared hole to a workpiece. The first cutting edges are formed in a tip side of the drill. The first point angle and each first relief angle of the first cutting edges continuously or intermittently decrease from the tip side toward a rear end side of the drill. The second cutting edges ream the prepared hole. The second cutting edges are formed at positions away in the rear end side from the first cutting edges. The second cutting edges have the second relief angles at a maximum diameter position. The deflection reducer reduces deflection of the second cutting edges. The deflection reducer is formed between the first cutting edges and the second cutting edges. The deflection reducer is inserted into the prepared hole.

The invention relates to a drill tip (2), comprising a center (4), at which a chisel edge (6) is arranged, and comprising a main cutting edge (8), which adjoins the chisel edge (6) and runs outward from the center (4). A rake angle is formed along the chisel edge (6) and the main cutting edge (8). The main cutting edge (8) has an inner portion (10), which adjoins the chisel edge (6) and is arranged within the center (4). The main cutting edge (8) has an outer portion (12), which outwardly adjoins the inner portion (10) and is arranged outside of the center (4). A point thinning (16) is formed on the drill tip (2), which point thinning is curved in such a way that the inner portion (10) runs arcuately from an outer edge of the center (4) toward the chisel edge (6). The invention further relates to a method for producing a drill tip (2) of this type.

A drill according to a non-limiting aspect may have a body, a cutting edge, a rake face, and a groove. The cutting edge may have a curved chisel edge, a pair of first cutting edges, and a pair of second cutting edges. The second cutting edge may have a first portion extending from the chisel edge and a second portion extending from the first portion toward the first cutting edge. The rake face may have a first region extending from the first portion and a second region extending from the second portion. A first rake angle of the first region may be zero or a negative value. A second rake angle of the second region may be a negative value. An absolute value of the second rake angle may be greater than an absolute value of the first rake angle.

In this drill, a wall face of a chip removal groove includes a first wall face having a concave curve shape and a second wall face having a straight line shape in a cross section orthogonal to an axis of the drill main body, an extension line of a straight line of the second wall face extends in a direction opposite to a drill rotation direction as the straight line of the second wall face goes to an outer periphery side of the drill main body with respect to a radius line connecting an outer peripheral end of the second wall face and the axis with each other, the cutting edge includes a first cutting edge having a concave curve shape and a second cutting edge having a straight line shape which intersects with the first cutting edge at an obtuse angle.