Patent ID: 7322777

Claim:
A cutting tool with a tool shank which supports a cutting insert in the form of a disposable perforated plate comprising a hard cutting material comprising one of: tungsten carbide or oxide ceramic, with a feed device that acts transverse to the axis of a hole in the perforated plate in the feed direction on the perforated plate as an adjustment means for the positioning of the perforated plate on the tool shank, and with a screw that projects through the plate hole of the perforated plate and with its screw head braces the perforated plate against a contact surface on the tool shank and, projecting through a bolt hole of the tool shank, is engaged with its screw thread in the nut thread of a retaining lock nut, which screw and retaining lock nut together form a screw fastener means, which retaining lock nut is supported on the side facing away from the perforated plate seat against the screw pressure and so that it cannot rotate around the screw axis on the tool shank, mutual stop surfaces of the screw head and the perforated plate on the one hand and of the retaining lock nut and tool shank on the other hand, as a result of their shapes, permit a mobility that follows the feed movement to provide a rotational mobility of the screw fastener means with respect to the tool shank and with respect to the perforated plate; a plane of rotational movement is defined approximately by the feed direction of said feed device and the axis of said bolt hole; said screw head comprises flanks that taper along the direction in which said screw head is inserted into the plate hole; said flanks are configured to contact and apply pressure to the interior surface of said plate hole; the inside diameter of said plate hole tapers in the insertion direction of said screw head; at least one of; said flanks and the interior surface of said plate hole have a concave surface; said retaining lock nut comprises a head portion having flanks that taper in the tightening direction of the screw threads of said retaining lock nut; said bolt hole has an annular shoulder; said flanks of said head portion of said retaining lock nut are configured to press against said annular shoulder of said bolt hole; and at least one of: said flanks and said annular shoulder have a concave surface.