Disposable cutting insert and tool holder therefor

In a turning tool for use in a lathe having a lathe cutting feed support;

• a selectably indexible cutting tool insert,
• a tool holder for said cutting tool insert having an elongated generally horizontally extending shank,
• said tool holder being mounted on and moved by said lathe cutting feed support for inward and lateral cutting movement relative to a journal, and having a mounting recess formed in one end thereof facing upwardly and toward the work to be turned during a normal operation of the cutting tool and having compound angled mounting surfaces at the base of said recess for positioning the cutting tool insert in an operative orientation,
• means accessible from the top of said cutting tool insert within the limits of said insert and having interengagement with said tool holder and engaging said cutting tool insert for fixedly securing said cutting tool insert to said recess,
• said cutting tool insert having parallel selectable mounting surfaces whereby the insert may be indexibly rotated and overturned to provide a plurality of operable cutting edges and having a plurality of side walls disposed at uniform angles relative to each other and extending perpendicular to said parallel mounting surfaces,
• each side wall being interconnected by a nose-cutting radius having a pair of spaced cutting flats formed thereon and extending between the parallel mounting surfaces with one of said cutting flats disposed in a forward cutting position in each indexible position of the cutting tool inserted and providing a finish cutting flat extending parallel to the direction of lateral feed movement of the cutting tool,
• each parallel mounting surface of the insert including a stepped nose chip breaker formed adjacent the nose-cutting radius for cooperation therewith and with said cutting edge flats and a stepped chip breaker extending along each side wall of the cutting tool insert for cooperation therewith between a pair of nose chip breakers,
• said stepped chip breakers extending along side walls being disposed at different elevational levels relative to said nose chip breakers to provide a stepped relationship therebetween.