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.

A drill bit (100) having a longitudinal axis (101) and to be rotated about the axis (101) in a drilling direction (102) to perform a drilling operation. The drill bit (100) comprises a body (120) having a longitudinal length with a proximal end (121) and a distal end (122). The body (120) has a diameter. A tapered tip (110) extends from the proximal end (121) and terminates in an apex (111) at an end of the drill bit (100). The drill bit (100) also comprises a plurality of flutes (140) with each flute (140) extending helically along the body (120) into the tip (110). The drill bit (100) also comprises a land (150) between each of the flutes (140) and extends to the tip (110). The drill bit (100) also comprises a plurality of tip faces (190) on the tip (110) and extends from a corresponding land (150) to the apex (111), where each of the tip faces (190) has a tip face leading edge (173) and a tip face trailing edge (174). Each of tip face leading edges (173) forms an intersection with an adjacent one of the flutes (140) to provide a plurality of primary cutting edges (175). In a tip cross-sectional plane extending perpendicular to the axis (101) through each of the primary cutting edges (175), each of the primary cutting edges (175) lies on a circle extending about the axis (101) and each of the tip face trailing edges (174) lies entirely within the circle. Each of the flutes (140) helically extends in an opposite direction to the drilling direction (102).

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.

A tapered countersink drill bit includes at least two screwing knifes and at least one two screwing trenches and a rod body; a length of an edge of the left lateral side of each screwing knife being shorten than that of an edge of the right lateral side thereof; each screwing knife including a front drilling head; a tapered portion formed at a backside of the front drilling head; a rear drilling head formed at a backside of the tapered portion; the screwing angle of each screwing knife being identical from the front drilling head to the rear drilling head; and a screwing angle of each screwing trench being identical from the front drilling head to the rear drilling head; a width between two adjacent knifes at a front end of the rear drilling head being longer than a width between two knifes at rear ends of two rear drilling head.

A drill bit (100) having a longitudinal axis (101) and to be rotated about the axis (101) in a drilling direction (102) to perform a drilling operation. The drill bit (100) comprises a body (120) having a longitudinal length with a proximal end (121) and a distal end (122). The body (120) has a diameter. A tapered tip (110) extends from the proximal end (121) and terminates in an apex (111) at an end of the drill bit (100). The drill bit (100) also comprises a plurality of flutes (140) with each flute (140) extending helically along the body (120) into the tip (110). The drill bit (100) also comprises a land (150) between each of the flutes (140) and extends to the tip (110). The drill bit (100) also comprises a plurality of tip faces (190) on the tip (110) and extends from a corresponding land (150) to the apex (111), where each of the tip faces (190) has a tip face leading edge (173) and a tip face trailing edge (174). Each of tip face leading edges (173) forms an intersection with an adjacent one of the flutes (140) to provide a plurality of primary cutting edges (175). In a tip cross-sectional plane extending perpendicular to the axis (101) through each of the primary cutting edges (175), each of the primary cutting edges (175) lies on a circle extending about the axis (101) and each of the tip face trailing edges (174) lies entirely within the circle. Each of the flutes (140) helically extends in an opposite direction to the drilling direction (102).

A cutting tool and method of manufacturing a tool including determining desired flowrates to cutting edges. The method includes calculating pressure drop and passage dimensions for each of an nth-number of passages to the cutting edges based on I.sub.n=(P.sub.n*A.sub.n.sup.n)/(.sub.n*L.sub.n), wherein I.sub.n is nth-passage flow rate, P.sub.n is nth-passage pressure drop, A.sub.n.sup.n is nth-passage cross-sectional area raised to a power n, the power n being equal to 1 or 0.5, .sub.n is nth-passage resistivity, and L.sub.n is nth-passage length. The method includes forming the nth-passages in the tool open to each cutting edge based on the nth-passage dimensions.

The invention relates to a tool for forming a drilled hole (B), comprising a shank that is rotatable or rotates about a tool axis (A), at least one first portion, which is rotatable or rotates about the tool axis (A), for producing and/or widening a drilled hole (B) by chip cutting, and a second portion, which rotates about the tool axis (A), for widening a drilled hole (B) without chip cutting, wherein the second portion is arranged behind the first portion in a direction of advance (V) of the tool. The invention additionally relates to a method for producing a drilled hole (B).

A cutting head rotatable about a first axis, comprising an intermediate portion and a tip portion. The intermediate portion has a plurality of leading edges defining a cutting diameter, and the tip portion has an axially forwardmost tip point and a plurality of front surfaces with outer and inner cutting edges. An outer rake surface adjacent to each outer cutting edge has a positive outer rake angle, and an inner rake surface adjacent to each inner cutting edge has a negative inner rake angle. Each outer rake surface is disposed on a head flute intersecting one of the leading edges, and each inner rake surface is disposed on a gash intersecting one of the head flutes. Each gash extends to a gash path end point located a first distance axially rearward of the tip point, and the first distance is greater than thirty percent of the cutting diameter.