Abstract: For producing hectically profiled workpieces (1) the helical profile (2) is first of all prefabricated by a milling treatment and is then finished by a grinding treatment of the profile surface. To achieve optimum machining qualities in an economic way, the grinding treatment is performed with a grinding tool (6, 12) adapted to the milling tool (3, 9) for the milling treatment in terms of shape, size, position of the axis of rotation and cutter arrangement.

Abstract: A multi-screw extruder consists of contra-rotating screws (20) inserted in a housing, whose flights (1) form intermeshing crests (2) and roots (3), and which have at least two axial sections (21, 22, 23) of flights each differing in number and pitch. To improve the manufacturing conditions, and to achieve uniform wear conditions over the screw length, adjacent axial sections (21, 22, 23) of a screw (20) verge into each other within an axial transition zone (24) free from annular grooves, where all roots (3) extend through the transition zone (24) while making turns (.alpha.) and forming ramifications or combinations (V), and at least one of the crests (2) begins or ends in the transition zone (24).

Abstract: To manufacture inner and outer parts for a rotary piston machine in which said parts have parallel axes and have interengaging helical engaging surfaces having convolutions in numbers differing by one and are operable to perform relative to each other rotating and eccentric revolving movements, the helical engaging surface of at least one of said parts is machined by a cutting tool, which is rotated about an axis which is parallel to and spaced from the axis of the part that is to be machined.

Abstract: Method and apparatus for machining the edges of sheet-like work pieces, using cutting elements disposed on rotating milling tools. The invention uses a conical tool with cutting tools on the conical jacket thereof. The active cutting tool which is closest to the work piece is located in the plane of the machining and a conical angle .alpha. in the range of about 150.degree. to about 180.degree. is utilized.