Reaming tool as well as a head and a cutting insert therefor

A reaming insert for a reaming tool including a driving rod, a head that has a rotationally symmetrical basic shape and is equipped with one or more detachable cutting inserts, and a clamping member, wherein the head comprises front and rear end surfaces, an envelope surface concentric with a centre axis (C), and a seat that is countersunk in the envelope surface and includes three support surfaces, one of which is a radial support surface and another one a tangential support surface, wherein the cutting insert is held fixed in the seat by means of the clamping member, wherein the cutting insert has the shape of a mirror-symmetrical polyhedron comprising six limiting surfaces, two opposite and mutually parallel ones of which are equidistantly separated from a central symmetry plane (SP1) and form chip surfaces that connect to limiting surfaces serving as clearance surfaces via alternately usable, identical cutting edges, wherein the cutting insert has a rhombic cross-sectional shape in the symmetry plane (SP1) and includes four clearance surfaces, which meet each other in pairs at obtuse angles (β) in two opposite corners, and which, along each individual chip surface, together with the same, form two cutting edges alternately usable by the indexing of the cutting insert, and wherein the seat, in addition to the radial and tangential support surfaces, includes a slope surface that forms an obtuse angle with the radial support surface, the reaming insert, comprising:

• four clearance surfaces
• wherein the reaming insert has a shape of a mirror-symmetrical polyhedron comprising six limiting surfaces, two opposite and mutually parallel ones of which are equidistantly separated from a central symmetry plane (SP1) and serve as chip surfaces that connect to limiting surfaces serving as clearance surfaces via alternately usable cutting edges,
• wherein the reaming insert has a rhombic cross-sectional shape in the symmetry plane (SP1), and
• wherein the four clearance surfaces meet each other in pairs at obtuse angles (β) in two opposite corners, and which, along each individual chip surface, together with the same, form two cutting edges alternately usable by the indexing of the cutting insert.

A rotationally symmetrical tool head for a reaming tool including a driving rod, a head that has a rotationally symmetrical basic shape and is equipped with one or more detachable cutting inserts, and a clamping member, wherein the head comprises front and rear end surfaces, an envelope surface concentric with a centre axis (C), and a seat that is countersunk in the envelope surface and includes three support surfaces, one of which is a radial support surface and another one a tangential support surface, wherein the cutting insert is held fixed in the seat by means of the clamping member, wherein the cutting insert has the shape of a mirror-symmetrical polyhedron comprising six limiting surfaces, two opposite and mutually parallel ones of which are equidistantly separated from a central symmetry plane (SP1) and form chip surfaces that connect to limiting surfaces serving as clearance surfaces via alternately usable, identical cutting edges, wherein the cutting insert has a rhombic cross-sectional shape in the symmetry plane (SP1) and includes four clearance surfaces, which meet each other in pairs at obtuse angles (β) in two opposite corners, and which, along each individual chip surface, together with the same, form two cutting edges alternately usable by the indexing of the cutting insert, and wherein the seat, in addition to the radial and tangential support surfaces, includes a slope surface that forms an obtuse angle with the radial support surface, the tool head comprising:

• front and rear end surfaces;
• an envelope surface concentric with a centre axis (C);
• and
• a seat for the receipt of a cutting insert, the seat countersunk in the envelope surface and includes three support surfaces, one of which is a radial support surface and another one a tangential support surface,
• wherein the seat, in addition to said radial and tangential support surfaces, includes a slope surface that forms an obtuse angle with the radial support surface.