Metal spinning

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Metal Spinning is a process by which circles of metal are shaped over mandrels (also called forms) while mounted on a spinning lathe by the application of levered force with various tools. It is performed rotating at high speeds on a manual spinning lathe or performed by CNC controlled automated spinning machines. The flat metal disc is clamped against the mandrel and a series of sweeping motions then evenly transforms the disc around the mandrel into the desired shape.

Metal spinning ranges from an artisan's specialty to the most advantageous way to form round metal parts for commercial applications. Artisans use the process to produce architectural detail, specialty lighting, decorative household goods and urns. Commercial applications range from rocket nose cones to public waste receptacles. Other methods of forming round metal parts include hydroforming, stamping and forging or casting. Hydroforming and stamping generally have a higher fixed cost, but a lower variable cost than metal spinning. Forging or casting have a comparable fixed cost, but generally a higher variable cost. As machinery for commercial applications has improved, parts are being spun with thicker materials in excess of 1" thick steel.

The basic hand metal spinning tool is called a spoon, though many other tools (be they commercially produced, ad hoc, or improvised) can be used to effect varied results.spinning tools can be made of hardened steel for using with aluminium or solid brass for spinning stainless steel/mild steel. Commercially, rollers mounted on the end of levers are generally used to form the material down to the mandrel in both hand spinning and CNC metal spinning. Rollers vary in diameter and thickness depending the intended use. The wider the roller the smoother the surface of the spinning, the thinner rollers can be used to form smaller radii.

The mandrel/chuck can be made from wood, steel alloys, or synthetic materials. The choice of material is dictated by the hardness of the material to be spun and by how many times the tool is expected to be used.

Metal spinning can be accomplished using a wide variety of materials from soft tempered aluminum and copper to structural plate steel and stainless steels.

The manual lathe in question is sometimes a regular woodworking lathe, although a wilson lathe is the most common manual spinning lathe in the UK. The mandrel having been formed from wood on the lathe or steel chuck machined on a CNC lathe previous to mounting on the metal stock. Cutting of the metal is done by hand held cutters, often foot long hollow bars with tool steel shaped/sharpened files attached. This is dangerous and should only be done by skilled trademen. All stock sizing is done prior to the spinning.

[edit] Safety Considerations

Care must be taken to not touch the spinning metal with one's hands until the metal edge has been "turned over" (rolled to a rounded edge so that the bare edge of the metal stock is protected). This caveat is mentioned specifically because wood turners are accustomed to touching the spinning wood in the lathes (once it reaches relative smoothness) to monitor their progress. This practice is very dangerous in metal spinning.