Machinery's Handbook, 31st Edition
Spinning
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Fig. 24. Conventional Spinning Shear Spinning.— Shear spinning is the process of forming complex shapes such as cones with tapering walls or symmetrical-axis curvilinear shapes such as the nose cones of missiles. This process achieves a deliberate and controlled reduction in blank thickness (Fig. 25), as opposed to a limited reduction of blank thickness in conventional spinning. The shear forming roller or rollers achieve local metal flow, which applies a pressure on the blank against the support from the steel mandrel. Special shear forming rollers control the material’s flow, and they move the free material parallel to the axis of the mandrel. The remaining portion of the blank, which does not take part in the actual deformation, remains always at right angles with respect to the axis of rotation and does not change its external diameter. The material flow takes place in the axial direction. The wall of the workpiece is produced from the reduction in blank thickness, but the diameter of the blank stays constant, as shown in Fig. 25 . The thickness of the initial blank depends on the angle of the final part and the finished wall requirements and can be calculated by the formula: (50) where T = thickness of the initial blank (inch or mm); T w = wall thickness of the spun part (inch or mm); and, α = half angle of cone. The bottom and the flange maintain their original thickness. A particular advantage is that the surface finishes achieved are comparable to those achieved with grinding or fine turning. The accuracy of the shape and the dimensional repeatability are excellent. sin T T w α =
Fig. 25. Shear Spinning Tube Spinning.— Tube spinning is used to reduce the wall thickness of a hollow cylindri cal blank while it is spinning on a cylindrical mandrel using spinning tools (Fig. 26). Applying the spinning tool to the cylindrical blank internally or externally achieves reduction of the workpiece wall, and this reduction in turn results in an increase in the workpiece’s length. Workpieces may be spun either forward or backward.
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