Abstract: The drill of the invention comprises a drill head having at least one guide pad, at least one outer cutting insert located at the periphery of the drill head surface and at least one inner cutting insert, having an active cutting edge, located nearer to the center of the drill head surface. The active cutting edge of the inner insert is situated within the outer edge of the guide pad or pads. Preferably, a plurality of cutting inserts are so arranged on the drill head that the resulting cutting force at all engaged inserts is on a level with the outer end of the guide pads.

Abstract: The invention concerns a cutting insert, having the shape of an isosceles triangle, which comprises a polygonal flat plate the top and bottom surfaces of which intersect with two edge surfaces of equal length to define main cutting edges, and at least one other edge surface adjoining said two edge surfaces at two cutting corners while intersecting with the top and bottom surface at right angles. The plate has the shape of an isosceles triangle the base of which is formed by said other edge surface. Secondary cutting edges are provided. The invention also involves a rotary milling cutter provided with a plurality of the cutting inserts.

Abstract: The invention concerns a cutting insert adapted for a cutting tool having mechanical insert-replacing mechanism. The insert has angularly interrelated side surfaces,- for resting in a corresponding V-shaped pocket in the cutting tool, said side surfaces extending parallel to the main cutting edge of the insert.

Abstract: A tool holder for clamping an apertured cutting insert in an insert-receiving site in a holder body a provision of a clamping pin rotatably and pivotally received in a bore in the holder while extending into the aperture of the insert. The pin is axially disposed in the holder and provided with a threaded portion engageable in a locking plate fixed in an enlarged portion of the bore. When the pin is screwed into the locking plate it pivots into a position wherein the plate abuts against a shoulder abutment in the bore while a portion of the pin projecting into the insert urges the latter against lateral abutment in the site.