Abstract: A wood and plastic screw has an essentially cylindrical shank, a tip, and a thread extending along the shank as far as into a tip region. The thread comprises a tip-side and a head-side flank, with a head-side flank angle being larger than a tip-side flank angle. The tip-side flank angle remains approximately constant in a shank region and in the tip region whereas the head-side flank angle in the tip region is larger than that in the shank region.

Abstract: A device provided on machine tools for transmitting torque onto tools, comprising at least two diametrically opposite rotary driving grooves openly issuing at the end of the tool shank and rotary drivers engaging in these and at least one locking member being disposed in the tool seat to be radially movable for engagement in a locking groove in the tool shank closed at both ends in the axial direction, wherein the rotary drivers comprise a cross section tapered in the direction of the rotary axis to have a stepped shape and, respectively, at least two rotary driving surfaces mutually offset to have a stepped shape for reducing susceptibility to wear. A tool for insertion in such a device.

Abstract: A straddling dowel for securing a threadable element such as a bolt or a screw, comprises a substantially cylindrical body of a plastic material. The body includes a tubular neck portion and an expanding wedge portion which is held outwardly from the neck portion by a plurality of longitudinally extending bending straps connected between the neck portion and the expanding wedge portion. A straddling leg is disposed between adjacent bending straps and extends longitudinally between the neck portion and the wedge portion and it is provided with a wedging surface which faces a similar wedging surface of the wedge portion.