Extruded hard metal or ceramic rods

摘要

The extruded rod of hard metal or ceramics, with at least one spiral drilling passing through, has a smooth outer or mantle surface, without projections or recesses. A twisting unit (8) is within the mass flow of the extrusion mass (9) to give an even twisting motion to the material. The material then passes through a following polished channel (4), with a twist or nearly or totally free of twist to be extruded out through the jet. Thread material is inserted into the mass, with the twisting movement, to form the spiral drilling(s). Stretch threads are pref., according to the number of drillings required, extending into the channel (4). The thread material in the mass flow can be evaporated easily by a chemical or physical process, but which can be pressed into the mass at flow speed. The thread material is removed at the latest in a sintering process. The thread material is fed externally, under pressure, and is plasticised by pressure or increased temp., and remains in a plastic state through the application of further pressure and/or heat. The outer dia. of the thread material matches the inner dia. of the drilling(s) to be formed.