Metal Spinning on a Lathe

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While metal spinning can be performed by hand, using metal spinning machinery such as a lathe to achieve metal spinning results is a fairly common method used in both industrial and personal machine shops. Metal spinning employs a rotating metal disc to shape a workpiece by causing the metal to “flow” into a predetermined shape. This process is frequently used to create rounded metal parts and products, ranging from aerospace components to decorative household goods.

Its reliance on rotational metal forming makes metal spinning somewhat similar in principle to lathe metalworking. However, unlike lathe machining, metal spinning relies on a mandrel that complements the interior curvature of the workpiece, rather than a clamping device necessary for holding the metal blank in place. Despite these differences, many lathes can be fitted to perform metal spinning operations. It is important to note that the lathe manufacturer should be consulted before changing the machine’s settings, and that an accredited training program can develop one’s lathe operating and metal spinning skills to ensure safe and effective production.

Metal Spinning Operations

In its fundamental processes, metal spinning centers around a metal workpiece, or blank, held between a rotating mandrel and a spindle tool. As a mechanism rotates these components, spinning rollers are pressed against the workpiece using manual or automated control. The workpiece is then positioned against the mandrel, which shapes the metal into an intended design through a sequence of axial strokes delivered via rotation. This process may change the material thickness of the workpiece, and due to its unique methods, it may appear that the metal is “flowing” into shape as if it were malleable and soft.

Metal spinning typically results in parts that are symmetrical and have a circular cross-section, although these parts are often cut and reassembled into new products. The final component usually has a diameter smaller than that of the blank workpiece, but with a similar surface area. Although it was once limited to softer metals and short production runs, as in prototyping, current metal spinning methods can fabricate highly durable materials in high volumes. Likewise, size restrictions have become less of a concern. Metal spinning processes can now create components of several dozen feet in length and up to three inches thick, depending on the metal.

Lathe Design

While lathes can come in a variety of configurations, there are a few design characteristics common to most models. When adapting a lathe for metal spinning operations, a number of different components should be taken into consideration. Though not all of them may need reconfiguring, some of the general lathe components involved in metal spinning include:

• The Bed: A lathe bed is a horizontal or vertical beam supporting the tooling devices on both ends of the machine. When adapted for metal spinning, it serves merely as a base for the headstock and tailstock.
• The Headstock: Located at one end of the bed, the headstock is essentially a frame for holding the lathe spindle and a series of rotating shaft bearings
• The Tailstock: The tailstock is positioned on the opposite end of the bed and is aligned with the headstock. It contains a clamping device that holds a metal disc parallel to the bed and presses it against the workpiece during fabrication.
• The Spindle: A spindle is responsible for holding and rotating the workpiece during operations. It consists of a main shaft that attaches to the rotating bearings, and a backplate that—when adapted to metal spinning—secures the workpiece to keep it from shifting around during fabrication.
• The Power System: This is the unit that drives both the rotational force and the tooling components in a lathe. It is usually a motor that is measured in RPM (rotations per minute) and in horsepower.

Adapting a Lathe for Metal Spinning

Although many types of lathes can be reconfigured to perform metal spinning, special skill training and manufacturer recommendations should always be followed before attempting any alterations. To illustrate how these changes are made, it may be helpful to examine a typical procedure used for converting a small metal-turning lathe into a metal spinning machine.

One of the first steps would be to build and install a fulcrum holding device into the lathe bed. This can be a solid metal bar inserted through a secure slot and attached with a complementary bar bolted to the underside of the bed, forming a stabilizing bridge. Next, the portion of the chuck used for clamping the workpiece may be replaced with a backplate to which the workpiece can be bolted or centered. An adjustable sliding tailstock may need to be installed, but many lathes already come equipped with such features. Finally, the forming tool may be shaped from steel rods or a symmetrical wooden mandrel built for the intended component design. While this process may be useful for converting a metal-turning lathe into a metal spinning unit, some fabricators prefer using a woodworking lather, which requires minimal changes to perform metal spinning projects.

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