Cutting insert and rotary cutting tool including same

A rotary cutting tool for milling a workpiece, comprising:

• a cylindrical tool body having two rows of helical flutes formed at a longitudinal front end portion thereof;
• a pair of cutting inserts replaceably mounted on the tool body;
• and
• a pair of screws configured to respectively fix the pair of cutting inserts to the tool body,
• wherein each of the pair of cutting inserts includes:
• an upper surface;
• a lower surface opposite to the upper surface and including a ridge portion, and a first inclined surface and a second inclined surface positioned on both sides of the ridge portion as a boundary and having asymmetric shapes with respect to the ridge portion;
• a first side surface and a second side surface configured to connect the upper surface and the lower surface;
• a mounting hole formed to penetrate the upper surface and the lower surface so that each of the pair of screws is fitted to the mounting hole, the mounting hole having a center (CP);
• a central axis (CL) passing through the center (CP) of the mounting hole and extending in an extension direction of the mounting hole, wherein the cutting insert lacks 180° rotational symmetry about the central axis (CL);
• a first corner portion and a second corner portion provided at both ends of the upper surface where the first side surface and the second side surface meet;
• a first cutting edge formed between the first side surface and the upper surface and including a peripheral edge extending in a curved shape from the first corner portion;
• and
• a second cutting edge formed between the second side surface and the upper surface and including a center edge extending in a curved shape from the second corner portion,
• a first insert pocket and a second insert pocket for accommodating the pair of cutting inserts are formed in the two rows of helical flutes, respectively,
• the pair of cutting inserts includes a first cutting insert mounted on the first insert pocket such that the first corner portion is positioned in a forward axial direction in which a front end of the tool body is oriented, whereby the peripheral edge of the first cutting insert is positioned in a radially outward direction and the forward axial direction of the tool body with respect to the center edge, and
• the pair of cutting inserts includes a second cutting insert mounted on the second insert pocket such that the second corner portion is positioned in the forward axial direction, whereby the center edge of the second cutting insert is positioned in the radially outward direction and the forward axial direction of the tool body with respect to the peripheral edge.