Skruv där skruvskallen är försedd med ett invändigt spår vars djup överstiger skruvhuvudets halva höjd

摘要

The present invention relates to a screw head 1 with a contact surface 6 and contact organs 9 for turning of the screw about its longitudinal axis 12 by means of tools. From the screw head protrudes a screw shaft 2 with a threaded portion 5. Into the screw head there protrudes a screw shaft 2 with a threaded portion 5. Into the screw head there protrudes at the contact surface a ring-shaped track 11 and exhibits in the axial direction of the screw a depth a which exceeds the radial width b of the track. In this way the screw head 1 is divided into a peripheral outer compression portion 18 positioned radially outside of the track and an expansion portion 19 positioned radially inside of the track. These two portions are arranged to elastically pre-tense the screw it is screwed into an object.