Provided are a cutting insert and a tool holder on which the cutting insert is provided. The cutting insert includes a circular upper surface, a circular lower surface, a cylindrical lateral surface for connecting the upper surface and the lower surface, an upper cutting edge formed between the upper surface and the lateral surface, a lower cutting edge formed between the lower surface and the lateral surface, and a plurality of rotation-preventing parts provided at the lateral surface so as to prevent the cutting insert from rotating with respect to the tool holder. Each rotation preventing part includes an inner curved surface recessed toward the center of the lateral surface and convexly rounded so as to form concentric circles in conjunction with the lateral surface, and a stepped rotation-preventing surface parallel to the axial direction of the insert and connecting the inner curved surface and the lateral surface.

Provided are a cutting insert and a tool holder on which the cutting insert is provided. The cutting insert includes a circular upper surface, a circular lower surface, a cylindrical lateral surface for connecting the upper surface and the lower surface, an upper cutting edge formed between the upper surface and the lateral surface, a lower cutting edge formed between the lower surface and the lateral surface, and a plurality of rotation-preventing parts provided at the lateral surface so as to prevent the cutting insert from rotating with respect to the tool holder. Each rotation preventing part includes an inner curved surface recessed toward the center of the lateral surface and convexly rounded so as to form concentric circles in conjunction with the lateral surface, and a stepped rotation-preventing surface parallel to the axial direction of the insert and connecting the inner curved surface and the lateral surface.

A cutting insert includes a base body and a coating layer, and also includes a rake surface, a flank surface, and a cutting edge located along an intersecting ridge therebetween. The rake surface includes an outer peripheral part and a middle part protruded relative to the outer peripheral part. The middle part includes a constraining surface. The outer peripheral part includes a first breaker part, a second breaker part, and the third breaker part adjacent to the constraining surface. The constraining surface is configured by the base body and the coating layer does not exist at the constraining surface. A skewness Rsk of a roughness curve at the constraining surface is −1.5 μm to −0.5 μm. A skewness Rsk at the third breaker part is −0.2 μm or less. The skewness Rsk at the constraining surface is smaller than the skewness Rsk at the third breaker part.

A cutting insert includes a base body and a coating layer, and also includes a rake surface, a flank surface, and a cutting edge located along an intersecting ridge therebetween. The rake surface includes an outer peripheral part and a middle part protruded relative to the outer peripheral part. The middle part includes a constraining surface. The outer peripheral part includes a first breaker part, a second breaker part, and the third breaker part adjacent to the constraining surface. The constraining surface is configured by the base body and the coating layer does not exist at the constraining surface. A skewness Rsk of a roughness curve at the constraining surface is −1.5 μm to −0.5 μm. A skewness Rsk at the third breaker part is −0.2 μm or less. The skewness Rsk at the constraining surface is smaller than the skewness Rsk at the third breaker part.

A method of milling a piece of raw steel stock comprising: arranging a minimum of four solid pole extensions on top surface segments of a magnetic chuck such that the solid pole extensions are relatively evenly distributed under a piece of raw steel stock and within 2 inches of a perimeter of the piece of raw steel stock; arranging multiple mobile pole extensions beneath the piece of raw steel stock and on every other top surface segment of the magnetic chuck under the piece of raw steel stock that is not occupied by the solid pole extensions but beneath the piece of raw steel stock, each of the multiple mobile pole extensions having a biased top portion that contacts the piece of raw steel stock; and milling the piece of raw steel stock with a face mill that generates steel chip as swarf.

There is provided a cutting insert which is capable of cutting by using either one of both surfaces and is stably supported by a tool body. Each of a first end surface and a second end surface of a cutting insert includes a first inclined surface which is inclined from a diagonal line by which a corner portion connecting a first peripheral side surface and a second peripheral side surface and a corner portion connecting a third peripheral side surface and a fourth peripheral side surface are joined toward a corner portion connecting the first peripheral side surface and the fourth peripheral side surface such that a distance to an imaginary plane decreases, and a second inclined surface which is inclined from the diagonal line toward a corner portion connecting the second peripheral side surface and the third peripheral side surface such that a distance to the imaginary plane decreases.

There is provided a cutting insert which is capable of cutting by using either one of both surfaces and is stably supported by a tool body. Each of a first end surface and a second end surface of a cutting insert includes a first inclined surface which is inclined from a diagonal line by which a corner portion connecting a first peripheral side surface and a second peripheral side surface and a corner portion connecting a third peripheral side surface and a fourth peripheral side surface are joined toward a corner portion connecting the first peripheral side surface and the fourth peripheral side surface such that a distance to an imaginary plane decreases, and a second inclined surface which is inclined from the diagonal line toward a corner portion connecting the second peripheral side surface and the third peripheral side surface such that a distance to the imaginary plane decreases.

A cutting tool includes a cutting insert having an anti-rotation stopping indent formed in a transition between a bottom surface and a side surface thereof and includes a first stop surface. The insert seat has at least one anti-rotation stop, which protrudes with respect to a side wall of the insert seat and includes a second stop surface. The anti-rotation stop is arranged to inhibit rotation of the cutting insert in the insert seat by contact between the first and second stop surfaces. The second stop surface is completely located within the anti-rotation stopping indent when the cutting insert is mounted. As seen in a section perpendicular to a common central axis, an angle of less than 180° is formed between a tangent to the second stop surface and a tangent to the first duct at a transition between the two.

A cutting tool includes a cutting insert having an anti-rotation stopping indent formed in a transition between a bottom surface and a side surface thereof and includes a first stop surface. The insert seat has at least one anti-rotation stop, which protrudes with respect to a side wall of the insert seat and includes a second stop surface. The anti-rotation stop is arranged to inhibit rotation of the cutting insert in the insert seat by contact between the first and second stop surfaces. The second stop surface is completely located within the anti-rotation stopping indent when the cutting insert is mounted. As seen in a section perpendicular to a common central axis, an angle of less than 180° is formed between a tangent to the second stop surface and a tangent to the first duct at a transition between the two.

A cutting insert may include a first surface, a second surface and a lateral surface. The first surface may have a polygonal shape and may include a first corner, a second corner, a third corner, a first side and a second side. The lateral surface may include a first lateral surface and a second lateral surface. At least a part of the first lateral surface may be located between the first side and the second surface. At least a part of the second lateral surface may be located between the second side and the second surface. The first lateral surface may be located further outside than the first side in a front view of the first surface. The first lateral surface may include a first region located closer to the second lateral surface as coming closer to the second surface.