Throw-away insert and face milling cutter

A face milling cutter comprising:

• a rotatable cutter body having a plurality of gullets in the outer periphery thereof and a plurality of throw-away inserts,
• each of said throw-away inserts comprising an upper half portion and a lower half portion which are integral with and identical in shape and dimension to each other, each of said portions including an upper surface having a substantially parallelogrammic shape so as to define two acute-angled corners, two cutting edges at the two acute-angled corners of the upper surface, respectively, and ridges at positions displaced outwardly from the center of the parallelogrammic upper surface and adjacent to said acute-angled corners, respectively, said cutting edges being disposed point-symmetrically with respect to the center of said parallelogrammic upper surface, and each of said cutting edges comprising a major cutting edge defined on one side of the parallelogrammic upper surface and a minor cutting edge defined on another other side thereof with the minor cutting edge constituting a said ridge and being contiguous to the major cutting edge, said major cutting edge and the minor cutting edge contiguous therewith subtending an angle of substantially 90.degree. in the plane of said upper parallelogrammic surface, said lower half portion having the configuration of said upper half portion as if said upper portion were turned over about an axis extending through the center of the upper surface thereof perpendicularly to said one side of the upper surface and then rotated by 3.degree.-7.degree. about an axis extending normally to said upper surface through the center of said upper surface, and each said insert having side surfaces intersecting said upper surfaces thereof at said minor cutting edges, respectively, at an acute angle, and
• said inserts being mounted in said gullets, respectively, with a respective said major cutting edge of each of said inserts being disposed on the outer periphery of the cutter body and the minor cutting contiguous with the respective major cutting edge being disposed downstream of the respective major cutting edge with respect to a direction of rotation of the cutter body, each said respective major cutting edge extending parallel to the axis of rotation of said cutter body, and each said minor cutting edge contiguous with said respective major cutting edge having a radial rake of -17.degree. to -10.degree. and said respective major cutting edge having an axial rake of 0.degree. to +8.degree..

A face milling cutter comprising:

• a rotatable cutter body having a plurality of gullets in the outer periphery thereof and a plurality of throw-away inserts,
• each of said throw-away inserts comprising an upper half portion and a lower half portion which are integral with and identical in shape and dimension to each other, each of said portions including an upper surface having a substantially parallelogrammic shape so as to define two acute-angled corners, two cutting edges at the two acute-angled corners of the upper surface, respectively, and ridges at positions displaced outwardly from the center of the parallelogrammic upper surface and adjacent to said acute-angled corners, respectively, said cutting edges being disposed point-symmetrically with respect to the center of said parallelogrammic upper surface, and each of said cutting edges comprising a major cutting edge defined on one side of the parallelogrammic upper surface and a minor cutting edge defined on another other side thereof with the minor cutting edge constituting a said ridge and being contiguous to the major cutting edge, said major cutting edge and the minor cutting edge contiguous therewith subtending an angle of substantially 90.degree. in the plane of said upper parallelogrammic surface, said lower half portion having the configuration of said upper half portion as if said upper portion were turned over about an axis extending through the center of the upper surface thereof perpendicularly to said one side of the upper surface and then rotated by 3.degree.-7.degree. about an axis extending normally to said upper surface through the center of said upper surface, and each said insert having side surfaces intersecting said upper surfaces thereof at said minor cutting edges, respectively, at an acute angle, and
• said inserts being mounted in said gullets, respectively, with a respective said major cutting edge of each of said inserts being disposed on the outer periphery of the cutter body and the minor cutting contiguous with the respective major cutting edge being disposed downstream of the respective major cutting edge with respect to a direction of rotation of the cutter body, each said respective major cutting edge being slightly inclined relative to said axis of rotation in such a direction that a trailing end thereof with respect to said direction of rotation is closer to said axis than a leading end thereof, and each said minor cutting edge contiguous with said respective major cutting edge having a radial rake of -17.degree. to -10.degree. and said respective major cutting edge having an axial rake of 0.degree. to +8.degree..