Metal spinning is a highly versatile and precise method used to shape metal into symmetrical, hollow forms. Starting with a simple flat disc and a rotating mandrel, this process can produce everything from shallow pans to deep cylindrical housings and conical parts. One of the key advantages of metal spinning is that it delivers seamless components with strong structural integrity, often while minimizing material waste.
In this guide, we’ll walk through the complete step-by-step journey of custom metal spinning, from raw material preparation to the finishing touches that complete a high-quality component.
1. Selecting the Right Material
Material choice plays a critical role in the success of a spinning project. Commonly used metals include aluminium, stainless steel, copper, brass, and titanium. Each material offers unique benefits and forming characteristics.
For example, aluminium is lightweight, corrosion-resistant, and easy to form into intricate shapes. Stainless steel provides superior strength and durability but requires more force during spinning. The decision ultimately depends on the required performance, strength, and appearance of the final part.
2. From Design to Blank Preparation
Every project begins with a detailed design that defines the geometry, material, tolerances, and finishing requirements of the part. This design is then translated into a physical starting point: a flat disc known as the blank.
The blank must be cut to the correct size to match the depth and dimensions of the finished piece. Precision at this stage ensures material efficiency, reduced forming time, and greater dimensional accuracy.
3. Mounting the Blank and Setting Up the Lathe
The prepared blank is securely mounted on a spinning lathe, held firmly against a mandrel. The mandrel acts as the shaping tool, creating the internal profile of the finished part. It is attached to the headstock of the lathe, while the blank is clamped in place with a pressure plate or follower block at the tailstock end.
Proper alignment is essential at this point. Even minor misalignment can lead to uneven wall thickness, visible defects, or complete part failure.
4. The Spinning Process
With the blank secured, the lathe rotates at speed, and a forming tool is applied to the surface of the disc. The tool gradually pushes the metal over the mandrel’s surface, shaping it into the required form. While this was traditionally done manually, modern systems often rely on CNC control for greater accuracy and repeatability.
The forming usually takes place in several passes. Each pass shapes the blank closer to the final profile. The key lies in applying the right amount of pressure at the right time. Excessive pressure risks wrinkling or tearing, while too little pressure prevents proper forming.
Because the metal work-hardens during the process, it may be necessary to anneal the part—heating and slowly cooling it—to restore ductility before continuing with deeper or more complex shapes.
5. Feathering, Finishing, and Planishing
Once the rough form is created, lighter feathering strokes are used to smooth out ripples or wrinkles. These controlled, gentle passes refine the surface while maintaining consistent wall thickness.
At this stage, the part has fully taken shape against the mandrel. A final planishing pass may be applied to eliminate minor surface imperfections, ensuring a smooth and uniform finish.
6. Trimming and Edge Treatment
Trimming removes excess material from the rim of the part using specialized cutting tools. The result is a clean, precise edge that matches the required specifications.
Depending on the intended application, edges may also undergo additional treatment—for example, beading for added strength, curling for safety, or flanging to connect with another component.
7. Quality Control and Removal
The completed part is carefully removed from the mandrel, usually by loosening the tailstock and sliding it off. In some cases, issues such as vacuum locking or thermal expansion may require additional methods, such as creating vent holes or applying gentle heating.
The spun part is then inspected to ensure dimensional accuracy, surface quality, and freedom from defects or deformation.
8. Optional Post-Spinning Processes
Although parts often emerge from the lathe with a high-quality surface, additional finishing may be necessary depending on the application. These processes can include polishing, plating, painting, or machining features such as holes, threads, or flanges. The goal is to deliver a component that is both structurally sound and fully functional for its intended use.
