Cutting insert and cutting tool

Abstract

In an end view, a cutting insertcomprises a first connecting partA which is inclined such that the first connecting partA travels in a first direction as it heads away from a second peripheral side surface partand approaches a fourth peripheral side surface part, and also comprises a second connecting partB which is connected to a center point serving as an end of the first connecting partA and which is inclined such that the second connecting partB travels in a third direction as it heads away from the second peripheral side surface partand approaches the fourth peripheral side surface part. A cutting edgecomprises: a first cutting edge partA which is formed on the first connecting partA so as to be distant, by a first distance L, from a virtual plane PRincluding a center point C; a second cutting edge partB which has, in a side view, a concave circular-arc shape having a second curvature radius smaller than a first curvature radius and which is formed on the second connecting partB so as to be distant, by a second distance Lgreater than the first distance L, from the virtual plane PR; and a third cutting edge partC connecting the first cutting edge partA and the second cutting edge partB.