SCREW AND METHOD OF ITS MANUFACTURE

摘要

A screw includes a barrel-shaped central pin is surrounded by a cylindrical bore having a conical bottom. The cylindrical insert is seated in the cylindrical bore. The top surface of the central pin is lowered below the top surface of the head. The walls of the pin (4) are convex towards the insert. Manufacturing the screw includes producing the threaded part with the head with the cylindrical recess with the cone-shaped bottom. The cylindrical insert terminates at one end with a bevel with an inclination angle of α=10-30°. The insert is introduced into the cylindrical recess. The upper part of the insert protruding from head of the screw is pre-shaped. The pin is upset using an appropriate tool and simultaneously the top surface of the pin is lowered below the top surface of the head.

主权项

1. A screw comprising a threaded part and a head in which an insert made of copper or aluminium, or copper alloy, or aluminium alloy is permanently seated, with grooves provided in the top surface of the head concentrically with the screw axis, wherein the screw comprises an upset central pin (4), the screw being barrel-shaped, surrounded by a cylindrical bore (3) having a conical bottom with an inclination angle of α from 10° to 30°, the screw having a cylindrical insert (5) with an axial through hole which is made of copper, aluminium, copper alloy, or aluminium alloy and is permanently seated in the cylindrical bore (3), wherein the top surface of the central pin (4) is lowered by d from 0.1 mm to 0.6 mm below the top surface of the head (2).