Spun Stainless Steel Bowl on a Lathe

Metal spinning forms a flat disc into a round, seamless shape without removing metal. A form block the shape of the inside of the bowl is mounted on the lathe, the disc is clamped against it by a pad on the tailstock, and as both spin at speed a levered tool or roller pushes the metal down over the block. Because the bowl ends up smaller across than the disc, the metal must thicken, stretch or wrinkle as it is pushed down. For stainless steel the tool is solid brass. The same method makes cookware, lighting, gas cylinders and brass instrument bells.