US Patent 10189097 Insert and indexable rotary cutting tool

A substantially parallelogramatic insert having a downward inclined main cutting edge and an auxiliary cutting edge in part of a long-side ridgeline and a short-side ridgeline adjacent to a pair of corner cutting edges of an upper surface; the main cutting edge being constituted by first to third straight cutting edges; the first to third straight cutting edges being connected in a bent-line shape with inward obtuse crossing angles when viewed from above, such that the second straight cutting edge is positioned outermost; and cutting edge angles β1, β2, β3 between the rake faces and flanks of the first to third straight cutting edges meeting the relation of β1>β2>β3.