Abstract: A forming tool for extrusion has a die (5), which has a forming cavity (6) having at least one critical reference value. The die (5) is surrounded by a biasing ring (8), which bears against it with radial pre-stress. The die (5) and the biasing ring (8) have tampered contact surfaces (11) and are displaceable relative to one another. The biasing ring (8) is surrounded by a reinforcement (9), which bears against it with radial pre-stress. The biasing ring (8) and the reinforcement (9) are mounted in a fixed position on a carrier (housing 1). The die (5) is displaceable relative to the carrier and capable of being locked, by locking means (15, 19) on the carrier, in positions that can be selected. By that means it is possible subsequently to carry out a fine adjustment of the critical reference value over a wide correction range.

Abstract: The moulding tool has an annular die providing a moulding cavity, an inner ring abutting against the die outer peripheral surface and an outer ring abutting against the inner ring outer peripheral surface. The inner ring is made of a material having a higher modulus of elasticity than the material from which the outer ring and die are made. Advantageously the inner ring is made of a carbide metal and the die and outer ring of steel and in the above described relationship to reduce the danger of fracture of the die.