In an end mill, eight peripheral cutting edges having a helical shape and a larger outer diameter than that of a shaft portion are in a cutting portion in a circumferential direction. For one peripheral cutting edge of the eight peripheral cutting edges, when a cut length of the peripheral cutting edge along an axial direction is L, a twist angle of the peripheral cutting edge is θ, and a circumferential distance at a lower end of the peripheral cutting edge between the peripheral cutting edge and another peripheral cutting edge adjacent to a tool rotation direction rear side of the peripheral cutting edge is a, n expressed by the following equation is approximately 1 for all of the eight peripheral cutting edges in at least a half region of the cut length from the lower end of the peripheral cutting edge.
n=(L×tan θ)/(2×a)

An indexable tangential cutting insert (4) for a milling tool comprises two opposing side surfaces (13) and four identical lateral surfaces (16, 17) extending between the side surfaces. Each lateral surface of the insert is provided with a support surface (32) configured to be supported by on one hand a corresponding support face of a pocket (3) of a tool body providing an axial support to the insert in two of eight index positions and on the other a corresponding support face of the pocket providing a tangential support to the insert in two other of said eight index positions. Each lateral surface (16, 17) of the insert is provided with a single said second support surface (32) being concave as seen in a direction perpendicular to said side surfaces and extending diagonally across the lateral surface.

In an aspect, a rotating tool includes a main body having a rod shape and extending along a rotation axis. The main body includes a first end, a second end, a twisted cutting edge located at a side of the first end, a twisted flute, a reverse twisted cutting edge located closer to the second end than the twisted cutting edge, and a reverse twisted flute. The reverse twisted flute is connected to the twisted flute. The twisted cutting edge includes a first part having a length from the rotation axis decreasing as approaching toward the second end.

In an end mill, eight peripheral cutting edges having a helical shape and g a larger outer diameter than that of a shaft portion are in a cutting portion in a circumferential direction. For one peripheral cutting edge of the eight peripheral cutting edges, when a cut length of the peripheral cutting edge along an axial direction is L, a twist angle of the peripheral cutting edge is , and a circumferential distance at a lower end of the peripheral cutting edge between the peripheral cutting edge and another peripheral cutting edge adjacent to a tool rotation direction rear side of the peripheral cutting edge is a, n expressed by the following equation is approximately 1 for all of the eight peripheral cutting edges in at least a half region of the cut length from the lower end of the peripheral cutting edge.

n=(Ltan )/(2a)

In an aspect, a rotating tool includes a main body having a rod shape and extending along a rotation axis. The main body includes a first end, a second end, a twisted cutting edge located at a side of the first end, a twisted flute, a reverse twisted cutting edge located closer to the second end than the twisted cutting edge, and a reverse twisted flute. The reverse twisted flute is connected to the twisted flute. The twisted cutting edge includes a first part having a length from the rotation axis decreasing as approaching toward the second end.

A rotatable cutting tool includes an elongate body and at least one helical flute extending over a length of the elongate body, the helical flute having a first end and a second end. The flute includes a cutting-edge with a first radius from a longitudinal center of the cutting tool, a trailing edge with a second radius from a longitudinal center of the cutting tool, wherein the second radius is smaller than the first radius, a flute surface between the cutting-edge and the trailing edge, the flute surface including a maximum radius at the cutting-edge and a plurality of foam chip shedding exclusions spaced along the cutting-edge of the helical flute, each of the foam chip shedding exclusions providing a gap in the cutting-edge where the radius within the gap is smaller than the first radius. The first radius defines a maximum tool cutting radius for the cutting tool. A gap distance between the foam chip shedding exclusions and the maximum tool cutting radius equals at least 15% of a radial height of the flute.

An insert portion (3) of a thread mill (1A) is fixed to a leading end portion of a body (2A) using screws (8). The insert portion (3) is configured by overlaying an insert (4) for finish machining and an insert (5) for rough machining. On respective mating faces of the inserts (4, 5), convex portions and concave portions of the mating face of the insert (4) are overlaid with concave portions and convex portions of the mating face of the insert (5). The thread mill (1A) can cut a female screw in a hole formed in a workpiece by performing right-hand cut down-cut milling, for example. The inserts (4, 5) simultaneously cut an inner peripheral surface of the hole, and the rough machining and the finish machining can thus be performed in a single pass. By the convex portions and the concave portions of the respective mating faces of the inserts (4, 5) being overlaid with each other, the inserts (4, 5) partially overlap in their respective thickness directions. As a result, a protrusion length of the insert portion (3) can be shortened.

An indexable tangential cutting insert for a milling tool includes two opposing side surfaces and four identical lateral surfaces extending between the side surfaces. Each lateral surface of the insert is provided with a support surface configured to be supported by, on one hand, a corresponding support face of a pocket of a tool body providing an axial support to the insert in two of eight index positions and, on the other, a corresponding support face of the pocket providing a tangential support to the insert in two other of said eight index positions. Each lateral surface of the insert is provided with a single second support surface being concave as seen in a direction perpendicular to said side surfaces and extending diagonally across the lateral surface.

An insert portion (3) of a thread mill (1A) is fixed to a leading end portion of a body (2A) using screws (8). The insert portion (3) is configured by overlaying an insert (4) for finish machining and an insert (5) for rough machining. On respective mating faces of the inserts (4, 5), convex portions and concave portions of the mating face of the insert (4) are overlaid with concave portions and convex portions of the mating face of the insert (5). The thread mill (1A) can cut a female screw in a hole formed in a workpiece by performing right-hand cut down-cut milling, for example. The inserts (4, 5) simultaneously cut an inner peripheral surface of the hole, and the rough machining and the finish machining can thus be performed in a single pass. By the convex portions and the concave portions of the respective mating faces of the inserts (4, 5) being overlaid with each other, the inserts (4, 5) partially overlap in their respective thickness directions. As a result, a protrusion length of the insert portion (3) can be shortened.

A rotatable cutting tool includes an elongate body having a longitudinal axis, a proximal end and a distal end and at least one helical flute extending over a length of the elongate body, the helical flute having a first end and a second end. The flute includes a cutting-edge with a first radius from a longitudinal center of the cutting tool, a trailing edge with a second radius from a longitudinal center of the cutting tool, wherein the second radius is smaller than the first radius, a flute surface between the cutting-edge and the trailing edge, the flute surface including a maximum radius at the cutting-edge and a plurality of foam chip shedding exclusions spaced along the cutting-edge of the helical flute, each of the foam chip shedding exclusions providing a gap in the cutting-edge where the radius within the gap is smaller than the first radius.