A rotary tool may include a body having a first part, a second part, a third part, a first cutting edge located at a first end, a flute extending from the first cutting edge toward a second end, and an outer peripheral surface. The outer peripheral surface in the third part may have a first portion. The third part may have a land face, and a second cutting edge located on a ridge line where a first portion and the land face intersect. The land face may have a first region in which a width increases from a side of the first end toward a side of the second end, and a second region that is located closer to the second end than the first region in which a width decreases from a side of the first end toward the second end.

A drill includes a leading end portion. The leading end portion is flat and has at least two cutting blades extending from a rotation center toward outside in a radial direction. The each cutting blade includes an arc-shaped portion. An inside linear portion is formed in a linear shape and connects to one end of the arc-shaped portion on the rotation center side. An outside linear portion is formed in a linear shape and connects to another end of the arc-shaped portion on an opposite side to the one end. The arc-shaped portion has a cutting edge provided with an arc-shaped portion chamfered surface. The inside linear portion and the outside linear portion each has a cutting edge provided with a linear portion chamfered surface. A drill axis direction width of the arc-shaped portion chamfered surface is smaller than a drill axis direction width of the linear portion chamfered surface.

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.

An object of the present invention is to provide helically fluted end mill with a diamond cutting surface. More particularly, it is an object of the present invention to provide a helically fluted end mill with helical grooves in the flutes that are filled with compacted polycrystalline diamond that can provide an effective cutting length based on the appropriate relationship between cutting length, diameter, the number of flutes, angle, and the number of polycrystalline diamond segments per flute.

A drill may include a main body having a bar shape extending from a first end to a second end. The main body may be rotatable around a rotation axis. The main body may include a cutting edge, a first flute extending from the cutting edge, and a second flute extending from the first flute. The first flute may include, in a cross section orthogonal to the rotation axis, a first portion having a concave curvilinear shape located at a rear side in a rotation direction, and a second portion having a convex curvilinear shape located at a front side in the rotation direction. The second flute has a concave curvilinear shape from an end portion located at a front side in the rotation direction to an end portion located at a rear side in the rotation direction in the cross section.

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.

A drill according to an embodiment includes a bar-shaped drill body extending along a rotation axis, a cutting edge located at a front end of the drill body, and a first flute extending spirally from the cutting edge toward a rear end of the drill body. The first flute includes a first region which is located close to the front end and has a helix angle 1, and a second region which is located closer to the rear end than the first region and has a helix angle 2 smaller than the helix angle 1. The second region includes an elongated protruding part along the first flute.

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.

A cutting tool is configured to cut and countersink a hole in a workpiece. The cutting tool includes a shank and a fluted body extending along an axis. The body includes a tip, a chamfer in an axially spaced relationship with the tip and a cross hole with a proximal end opening to the chamfer. The body has a cutting section extending between the tip and the chamfer, and a countersinking section extending along the chamfer. At the cutting section, the body includes at least one hole-cutting edge. At the countersinking section, the body includes a scalloped countersink-cutting edge along a junction of the chamfer and the proximal end of the cross hole.

A method for producing a twist drill has the following steps. A blank is shaped to form a semi-finished product. The semi-finished product is formed from a core, coaxial with the drill axis, having a radius and a number of webs, arranged on the core, having a height. The semi-finished product has a constant cross section along the drill axis. The webs have a first portion which adjoins the core and in which a width of the web remains constant or decreases in the circumferential direction with increasing radial distance from the drill axis. The webs have a second portion which adjoins the first portion and in which the width of the web increases in the circumferential direction with increasing radial distance from the drill axis. The webs of the semi-finished product are shaped into helical segments using a plurality of rolling tools that annularly enclose the semi-finished product and roll on the webs along the drill axis. The rolling tools have teeth that are inclined with respect to the drill axis. A height of the helical segments is less than the height the webs. Helical segments formed from adjacent webs are in contact with one another in a closing fold. The invention also relates to a twist drill.