Patent ID: 8777525

Claim:
Polygonal turning insert comprising: an upper side generally parallel to a reference plane; an under side, a plurality of clearance surfaces between the upper side and the under side; a cutting edge that is formed at least along the upper side and includes three part edges, wherein the three part edges include a nose edge situated in a corner of the insert and two main edges converging toward the corner, which individually are formed between a chip surface and a clearance surface; and a chip-guiding flank surface for each one of the part edges, wherein the chip-guiding flank surface includes a primary flank surface situated behind the nose edge along a bisector between the main edges and a pair of secondary flank surfaces situated inside the respective main edge, wherein the primary flank surface and the secondary flank surfaces lean in an upward direction from a lower boundary line, wherein the primary flank surface is convexly arched and delimited by an arched lower boundary line, which has an apex point facing the nose edge and is situated along the bisector and includes two mirror-symmetrical arc part lines, which extend from the apex point to a pair of opposite end points situated along a straight reference line that intersects the bisector at a right angle in a middle point between the end points, wherein a first distance between the midpoint and the individual end points is greater than a second distance between the midpoint and the apex point, and wherein an angle of inclination of the primary flank surface in arbitrary vertical sections through the midpoint decreases from a greatest value in a section along the bisector to a smallest value in a section through the individual end points.