Abstract: 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 ?, 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.

Abstract: A ball end mill according to the present invention includes an end mill body which is formed in a shaft shape, a plurality of convex arcuate end cutting edges which are disposed on a tip portion of the end mill body at intervals around an axis and form a hemispherical shape such that a rotational locus around the axis has a center on the axis, and a plurality of gashes which are respectively disposed to be adjacent to the plurality of end cutting edges in an end mill rotation direction around the axis. The plurality of end cutting edges includes a first end cutting edge longest among the plurality of end cutting edges, a second end cutting edge which is adjacent to the first end cutting edge in the end mill rotation direction and a third end cutting edge which is adjacent to the second end cutting edge in the end mill rotation direction.

Abstract: In order to form an internal thread having a concave surface having the same shape as that obtained by using a thread cutting blade having a convex surface without using such a thread cutting blade in formation of an internal thread hole in a mold component or the like using a thread milling cutter, a trimming blade has a leading-side flank surface extending from an axial tip side of a tool body to the rear side, a top surface formed continuously to the leading-side flank surface in the axial direction, and a trailing-side flank surface formed continuously to the top surface in the axial direction. Two or more chamfered surfaces are formed between the leading-side flank surface and the top surface and between the top surface and the trailing-side flank surface in the trimming blade.

Abstract: In a screw thread cutter, a screw thread-cutting edge is formed on an outer periphery of a tip portion of a cutter body. Finishing edge-thread ridge height from a tangent line passing through valley bottoms of second and third valley portions to outer peripheral ends of first and second finishing edges are equal to each other. A preceding edge-thread ridge height from the tangent line to an outer peripheral end of a preceding edge is lower than each of the finishing edge-thread ridge height. A first valley portion-depth from the outer peripheral end of the first finishing edge to the valley bottom of the first valley portion is deeper than a second valley portion-depth from the outer peripheral end of the second finishing edge to the valley bottom of the second valley portion.

Abstract: 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.

Abstract: A ball end mill according to the present invention includes an end mill body which is formed in a shaft shape, a plurality of convex arcuate end cutting edges which are disposed on a tip portion of the end mill body at intervals around an axis and form a hemispherical shape such that a rotational locus around the axis has a center on the axis, and a plurality of gashes which are respectively disposed to be adjacent to the plurality of end cutting edges in an end mill rotation direction around the axis. The plurality of end cutting edges includes a first end cutting edge longest among the plurality of end cutting edges, a second end cutting edge which is adjacent to the first end cutting edge in the end mill rotation direction and a third end cutting edge which is adjacent to the second end cutting edge in the end mill rotation direction.

Abstract: In a screw thread cutter, a screw thread-cutting edge is formed on an outer periphery of a tip portion of a cutter body. Finishing edge-thread ridge height from a tangent line passing through valley bottoms of second and third valley portions to outer peripheral ends of first and second finishing edges are equal to each other. A preceding edge-thread ridge height from the tangent line to an outer peripheral end of a preceding edge is lower than each of the finishing edge-thread ridge height. A first valley portion-depth from the outer peripheral end of the first finishing edge to the valley bottom of the first valley portion is deeper than a second valley portion-depth from the outer peripheral end of the second finishing edge to the valley bottom of the second valley portion.

Abstract: A multi-flute ball end mill of the present invention includes: a shank portion configured to rotate about a rotational axis; a cutting edge portion; three or more ball edges formed on the cutting edge portion; gashes formed between the ball edges; peripheral cutting edges continuous with end portions of the ball edges on the shank portion side; and flutes formed between the peripheral cutting edges continuously with the gashes. The degree of curvature of the ball edges is 35% to 55%. Each of the gashes includes four faces of a rake face of each of the ball edges, a gash wall face, a first gash face, and a second gash face. The second gash face is formed such that the closer the second gash face is to the rotation center point, the more inwardly the second gash face enters a second face of each of the ball edges.

Abstract: In order to form an internal thread having a concave surface having the same shape as that obtained by using a thread cutting blade having a convex surface without using such a thread cutting blade in formation of an internal thread hole in a mold component or the like using a thread milling cutter, a trimming blade has a leading-side flank surface extending from an axial tip side of a tool body to the rear side, a top surface formed continuously to the leading-side flank surface in the axial direction, and a trailing-side flank surface formed continuously to the top surface in the axial direction. Two or more chamfered surfaces are formed between the leading-side flank surface and the top surface and between the top surface and the trailing-side flank surface in the trimming blade.

Abstract: A multi-flute ball end mill of the present invention includes: a shank portion configured to rotate about a rotational axis; a cutting edge portion; three or more ball edges formed on the cutting edge portion; gashes formed between the ball edges; peripheral cutting edges continuous with end portions of the ball edges on the shank portion side; and flutes formed between the peripheral cutting edges continuously with the gashes. The degree of curvature of the ball edges is 35% to 55%. Each of the gashes includes four faces of a rake face of each of the ball edges, a gash wall face, a first gash face, and a second gash face. The second gash face is formed such that the closer the second gash face is to the rotation center point, the more inwardly the second gash face enters a second face of each of the ball edges.