A cutting tool having replaceable indexable cutting insert retained in insert pockets. Each insert pocket has a base wall and first and second rear sidewall sections. A generally circular recess having a peripheral wall extends downwardly from the base wall. The cutting insert comprises an upper surface, a side surface and a lower surface from which a cylindrical protrusion extends downwardly. A first abutment surface located on the first rear sidewall section abuts a first support surface located on the side surface of the cutting insert, a second abutment surface located on the second rear sidewall section abuts a second support surface located on the side surface of the cutting insert, and a third abutment surface located on the peripheral wall of the recess abuts a third support surface located on the cylindrical protrusion of the cutting insert.

A holder or nest for pin-type replaceable cutting inserts has a back face and a front face parallel to the back face for supporting a pin-type replaceable cutting insert of the type having a circular aperture centrally disposed therein. A pin extends perpendicularly to the front face of the holder, on which pin the cutting insert is received. The holder comprises an extension having a face coplanar with the back face of the holder itself. The extension further comprises a threaded aperture to receive a screw which serves to clamp the holder and the cutting insert into a recess in the cutter body.

A holder or nest for pin-type replaceable cutting inserts having a circular aperture centrally disposed therein, includes a pin extending perpendicularly to the face of the holder, the pin being cylindrical and being formed with a pair of discrete opposed axially-extending portions, each of the portions comprising a segment of a circular cylinder having a periphery less than 180.degree.. The radius of each of the portions is selected equal to the radius of the aperture in the cutting inserts. The portions meet in a plane normal to the face of the tool holder and disposed perpendicularly to the axis of the clamping screw which is threadedly receivable in the body of the holder. By this means the clamping force exerted by the screws, forces the insert to seat itself on the lateral surface of the one axially extending portion of the pin which is inwardly disposed in the cutter body, thereby to achieve positive seating of the insert on the pin in a direction perpendicular to the pin and parallel to the plane between the axially extending portions thereof.

A toolholder is disclosed consisting of a body having a recess extending inwardly from the periphery. The recess is formed having an inwardly extending front and back wall, defining a bottom wall therebetween. A shim is disposed in the recess with the back side abutting the back wall of the recess and being supported thereby, the shim having a protuberance on its front side for engaging a center hole of an insert. A pin member is imbedded in the bottom wall of a recess and located adjacent to, or in the region of, the front wall and means is provided for clamping the insert between the shim and bottom wall of the recess and the pin.

A cutting mill kit includes a basic body formed with a plurality of peripheral recesses which receive respective cassettes and cutting inserts and an annular support element which is provided with at least one formation receiving a respective gib. The gib provides an axial support for the cassette and has a width lesser than a width of the cassette.