A cutting tool includes one or more cutting portions. Each of the cutting portions has a cutting insert and an insert pocket for mounting the cutting insert. The insert pocket has a top surface with one or more projecting portions with a shape of serration, and a bottom supporting surface. The cutting insert has a top surface mating with said projecting portions of the insert pocket, and a bottom surface mating with the bottom supporting surface of the insert pocket. The top surface of the cutting insert has one or more outwardly sloped surfaces mating with the projecting portions of the insert pocket, and one or more inwardly sloped surfaces positioned off the projecting portions.