Abstract: A pneumatic hammer having a vibration attenuating hollow cylindrical member axially movable in a housing body, a striking piston axially movable within the cylindrical member, a stationary sealing sleeve engaging a portion of the outer surface of the cylindrical member, inlet air control means including an inlet passage in the wall of the cylindrical member, a slidable pressure ring cooperating with a pressure spring for urging the cylindrical member into a rest position in which the inlet air control means are disconnected from the inlet air channel and are connected instead to an outlet air channel in the housing body. Upon lifting the cylindrical member via a working tool, the passage to the outlet air channel is closed and the passage from the inlet air channel to the inlet air control means is opened and a normal operation of the hammer is initiated.

Abstract: The invention is directed to a clamping system for knives with angular cross-sections, especially suited for agricultural cutting operations in which a portion of the length of the sidepiece extending the cutting edge of the knife protrudes over the knife holder when the knife is clamped, with the clamping element engaging the knife in the area of its angular bend. This system allows for a reduction of knife thicknesses while maintaining other desirable characteristics, and provides the knife with greater strength in the area stressed by bending as compared with the unclamped position of the knife.

Abstract: Milling cutter head for making arcuate toothing, comprising a substantially disk-shaped carrier body that is surrounded by a locking ring, the body having therein one or more pairs of grooves of a stepped cross-section, for receiving a corresponding number of pairs of removable, axial milling cutters, in each pair one being an inner and one an outer cutter. These cutters have head cutting and flank cutting edges, and optionally head and flank clearance surfaces. The head cutting edges are made of overlap partially; the cutting edges are formed at intersecting points between the clearance surfaces. Both kinds of cutters have cylindrical body surfaces that include chip bearing surfaces and associated limiting surfaces, as well as optional supporting surfaces. The inclination angle defined between the chip bearing and the limiting surfaces is smaller than 90.degree.. The cutters are preferably rod-shaped and have quadrilateral cross-sections.