Diminishing/Reducing from a metal cylindrical blank

The techniques applied in diminishing, reducing or swaging are the same as for multi-pass metal spinning. The cylindrical shape of a part, with the base already being finish formed, is diminished or reduced to a smaller diameter by the necking-in roller, producing a profile of decreasing diameter. Stresses at the tangents are inevitable, tending towards buckling. As with traditional metal spinning, the spun metal is worked in an array of passes producing a dished shape which adds strength and hardiness to buckling. A spring-loaded tapered ring supports the edge and further assists this process.

An axial loading is created by the array of passes and the nose radius of the roller. This leads to added tensile stress, influencing final wall thickness of the spun metal.