A polygonal indexable cutting insert for cutting aluminum metal comprises rounded cutting corners with adjacent side surfaces joined at an angle of from about 33 to about 35 degress. Grooved recesses extending along each cutting edge have a particular geometry which includes a shallow descending surface followed by a steeply descending surface leading to the bottom of the grooved recess. An ascending surface directs the chip upwardly toward the top face and away from the insert and the cutting edge.
