Metal spinning is the process in which a metal sheet is held between the tail stock of a lathe and a rotating form block. The sheet is mounted in the head stock and rotated at a high speed while a constant, slow spinning tool that is mounted on the tool post, presses the sheet on to the form block. Lubricants like tallow, oil and wax are used in this process so the metal doesn’t stick to the machinery when you take it off. The lubricant also makes a nice finish on the part. If there are grooves on the part after it has been spun it may need to be finished with sandpaper or a file.
The procedure is not very precise and it is generally used when the production quantities are low and when the costs do not justify investing in deep drawing dies and tools. Semicircular, conical and square shapes can be spun.
In this process, a metal spinning lathe is used and metals such as sheet metal, aluminum, brass, copper, and stainless steel, can be used. An even force is applied to the metal with a tool while the metal rotates against the form (mandrel) at a high speed. This force creates a smooth form. A tool is used for leverage to work the part down against the mandrel. Operators use long-handled tools and hold them beneath the armpit so the body weight provides the force and the arms are kept free to guide the metal. There are many types of tools used in this process, but a tool called the sheep's nose is generally used for the forming and a device called a duck's bill is usually used for the finishing.
The process of metal spinning consists of three steps: breakdown, where 95 percent of the deformation is done; laying the metal on the form block where the remaining 5 percent of the deformation is done; and the final finishing, where the tool marks are removed. Various metals such as aluminum and magnesium alloys, low carbon steel, stainless steel, annealed nickel alloys, copper and brass can be spun. There is a maximum plate thickness. If anything goes beyond this thickness, spinning cannot be done and may lead to metal fracture.