US 12,226,840 B2
Rotary cutting tool cutting insert and rotary cutting tool
Kouki Matsubara, Itami (JP); Sachie Goto, Itami (JP); Kohei Ito, Itami (JP); and Toya Nonen, Itami (JP)
Assigned to SUMITOMO ELECTRIC HARDMETAL CORP., Itami (JP)
Appl. No. 17/433,606
Filed by Sumitomo Electric Hardmetal Corp., Itami (JP)
PCT Filed Sep. 2, 2020, PCT No. PCT/JP2020/033207
§ 371(c)(1), (2) Date Aug. 25, 2021,
PCT Pub. No. WO2022/049659, PCT Pub. Date Mar. 10, 2022.
Prior Publication US 2022/0339718 A1, Oct. 27, 2022
Int. Cl. B23C 5/10 (2006.01); B23B 51/00 (2006.01)
CPC B23C 5/10 (2013.01) [B23B 51/00 (2013.01); B23C 2200/0438 (2013.01); B23C 2200/203 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A rotary cutting tool cutting insert comprising:
a top surface;
a bottom surface located opposite to the top surface; and
an outer peripheral surface contiguous to each of the top surface and the bottom surface, wherein
a ridgeline between the top surface and the outer peripheral surface forms a cutting edge,
the cutting edge includes
a first line segment,
a second line segment opposed to the first line segment,
a third line segment inclined relative to each of the first line segment and the second line segment,
a fourth line segment opposed to the third line segment,
a first curved portion connecting the first line segment and the third line segment,
a second curved portion connecting the second line segment and the fourth line segment,
a third curved portion connecting the second line segment and the third line segment, and
a fourth curved portion connecting the first line segment and the fourth line segment,
a straight line along the first line segment and a straight line along the third line segment form an acute angle,
a straight line along the second line segment and a straight line along the fourth line segment form an acute angle,
the straight line along the second line segment and the straight line along the third line segment form an obtuse angle,
the straight line along the first line segment and the straight line along the fourth line segment form an obtuse angle,
each of the third curved portion and the fourth curved portion is larger in radius of curvature than the first curved portion and larger in radius of curvature than the second curved portion,
the top surface has a flat portion spaced apart from the cutting edge,
in the direction perpendicular to the bottom surface, the flat portion is located between the cutting edge and the bottom surface, and
an entirety of the top surface is not located above the cutting edge in the direction perpendicular to the bottom surface when a direction from the bottom surface toward the top surface corresponds to an upward direction.