Abstract: The invention relates to impact wrenches for tightening threaded joints comprising an impact clutch accommodated in a housing and having a hammer which is axially movable for imparting each blow, and a device for automatically limiting the number of blows to a pre-set number of blows. The device for automatically limiting the number of blows comprises a blow number setter, a movable member directly co-operating with the hammer and axially movable upon each axial displacement of the hammer so as to enable the axial displacement of the hammer until a pre-set number of blows are delivered, and a locking device for locking the movable member against displacement in the position preventing further axial movement of the hammer after the ultimate blow of the pre-set number of blows is delivered. Thus the possibility of imparting blows in excess is eliminated without deenergization of the impact wrench drive, and the construction of the impact wrench is simplified.

Abstract: A rotary tool having a working part and a shank. The working part is formed by at least two axial portions of which the first portion is made with the profile of a twist drill for making a pilot hole, and the second portion is disposed axially between the first portion and the shank. The second portion is made in such a manner as to enlarge the pilot hole upon entering it and to ensure self-feed of the tool in the axial direction. This permits substantial reduction of required force for axial feed of the tool, improves productivity and allows making holes of different diameter with one and the same tool.

Abstract: A pneumatic hammer is an impact tool to be used in the construction industry and in mechanical engineering for chipping metal, scaling welds and chipping castings. The pneumatic hammer comprises a housing accommodating a barrel axially movable relative thereto, and a hood which is axially biased by a spring. The barrel is adapted to receive a tool having a non-circular cross-section. The hood has a non-circular hole for passage of the tool. Intermediate members are disposed between the hood and the tool and are in contact with the tool and comprise bodies of revolution rotatably mounted in the hood. The intermediate members define the non-circular hole of the hood, the shape of the hole corresponding to the cross-sectional shape of the tool. With such construction, the sliding friction between the tool and the side wall of the hood is replaced by the rolling friction between the tool and the intermediate members thereby reducing vibrations and lowering heating of the tool.