A rotary cutting tool that implements a chip space in proportion to a feed-per-tooth is proposed. The rotary cutting tool includes a cutting part in which a plurality of cutting teeth and flutes are alternately formed, wherein a cross-section of the cutting part perpendicular to a central axis is divided into a plurality of cutting tooth spaces defining a section between cutting edges of adjacent cutting teeth on the basis of the central axis, such that all of the cutting tooth spaces are designed in different sizes, or some of the plurality of cutting tooth spaces are set in different sizes from the other cutting tooth spaces.

A rotary tool according to a non-limiting aspect has a body that has a rod shape extending from a first end to a second end and is rotatable about a central axis. The body has a first cutting edge positioned on the first end, a first flute extending from the first cutting edge toward the second end, a second cutting edge being on a side of the second end and on a side of an outer periphery with respect to the first cutting edge and being positioned away from the first cutting edge, and a second flute, extending from the second cutting edge toward the second end and being positioned along the first flute. The second flute has a projecting portion extending from a side of the first end toward a side of the second end.

A rotary cutting tool that implements a chip space in proportion to a feed-per-tooth is proposed. The rotary cutting tool includes a cutting part in which a plurality of cutting teeth and flutes are alternately formed, wherein a cross-section of the cutting part perpendicular to a central axis is divided into a plurality of cutting tooth spaces defining a section between cutting edges of adjacent cutting teeth on the basis of the central axis, such that all of the cutting tooth spaces are designed in different sizes, or some of the plurality of cutting tooth spaces are set in different sizes from the other cutting tooth spaces.

A cutting tool holder of the present disclosure includes a bar-shaped main body. The main body includes a first pocket to receive a first insert, a second pocket to receive a second insert, a first groove extending from the first pocket, and a second groove extending from the second pocket. The first groove includes a second opening located on a rear side in a rotation direction, and the second groove includes a fourth opening located on a rear side in the rotation direction in a cross section orthogonal to a rotation axis. An angle θ1 formed by the second opening and an outer peripheral surface of the main body is smaller than an angle θ2 formed by the fourth opening and the outer peripheral surface of the main body in a cross section orthogonal to the rotation axis.

A rotary tool according to a non-limiting aspect has a body that has a rod shape extending from a first end to a second end and is rotatable about a central axis. The body has a first cutting edge positioned on the first end, a first flute extending from the first cutting edge toward the second end, a second cutting edge being on a side of the second end and on a side of an outer periphery with respect to the first cutting edge and being positioned away from the first cutting edge, and a second flute, extending from the second cutting edge toward the second end and being positioned along the first flute. The second flute has a projecting portion extending from a side of the first end toward a side of the second end.

A step drill bit has a cutting head defining a longitudinal axis and having a plurality of steps having different effective diameters. First and second cutting edges are formed in the cutting head. The first cutting edge and the second cutting edge are arranged such that the bit is asymmetric in a plane perpendicular to the longitudinal axis relative to a plane containing the longitudinal axis. A rubbing surface is formed on each step where the rubbing surface extends to approximately the effective diameter of that step such that the first cutting edge, second cutting edge and the rubbing surface forms three points of contact with the side wall of the hole being cut.

A step bit according to some embodiments includes a body including one or more flutes having a cutting edge configured to cut a hole in a workpiece, and a plurality of steps provided on the body. The steps progressively increase in diameter from a first distal step to a terminal proximal step. One or more of the steps have first and second lands. An outer diameter of the first land is less than the outer diameter of the second land. A length of the first land is less than a length of the second land.

A twist drill having a shaft with a longitudinal axis, wherein the cutting tool includes a plurality of flutes extending about the longitudinal shaft along a helix angle and a plurality of lands adjacent the flutes. Each land has a cutting edge adjacent a corresponding flute and a margin (i.e. relief surface). A cutting point is adjacent a forward end of the shaft. A first, second and third forward cutting surfaces are adjacent the first, second and third cutting edges, respectively, and extend proximate the cutting point axially rearward for a predetermined length about the longitudinal axis of the shaft. The cutting edges are unequally angularly spaced from each other, and each forward cutting surface has a primary relief angle that are unequal to each other.

A step bit according to some embodiments includes a body including one or more flutes having a cutting edge configured to cut a hole in a workpiece, and a plurality of steps provided on the body. The steps progressively increase in diameter from a first distal step to a terminal proximal step. One or more of the steps have first and second lands. An outer diameter of the first land is less than the outer diameter of the second land. A length of the first land is less than a length of the second land.

A cutting tool holder of the present disclosure includes a bar-shaped main body. The main body includes a first pocket to receive a first insert, a second pocket to receive a second insert, a first groove extending from the first pocket, and a second groove extending from the second pocket. The first groove includes a second opening located on a rear side in a rotation direction, and the second groove includes a fourth opening located on a rear side in the rotation direction in a cross section orthogonal to a rotation axis. An angle 1 formed by the second opening and an outer peripheral surface of the main body is smaller than an angle 2 formed by the fourth opening and the outer peripheral surface of the main body in a cross section orthogonal to the rotation axis.