Metal spinning, also called conventional spinning or just spinning, is the forming of an axis-symmetric part over a rotating mandrel. Force is delivered by a tool with a rounded end or a roller. A flat, or possibly preformed, work piece is held between a mandrel and tail stock. As the apparatus rotates, the tool applies localized pressure to the work while it gradually moves up the mandrel. This causes the sheet metal work to be wrapped over the mandrel, thus taking its shape. Metal spinning is commonly performed cold, but in some cases parts may be subject to warm or hot spinning. Spinning is capable of producing large parts with diameters as high as 20 feet.
The tooling in a metal spinning operation is generally made from tool steel. The mandrel in some cases may be made of wood. Containers with bottle or tapered necks can be manufactured on collapsible mandrels, that are disassembled and removed from the formed parts. Set up costs for metal spinning are usually low. Conducting a spinning operation is relatively expensive on a per unit basis. Deep drawing is usually the main alternative manufacturing method to metal spinning, for producing parts. In contrast, deep drawing often requires a high initial investment for set up, while the cost of production per part is low. For these reasons, deep drawing is more useful for mass production of parts. Spinning is employed for small numbers of parts, unique, curved, or varied parts and large parts. Operator skill is important in metal spinning. CNC machinery is now replacing the operator in many cases. CNC spinning gives a high quality consistent product.