KRYTON Metals Blog

The Science Behind Spinning Metal

Manual and CNC lathes are a fixture in practically every machine shop or metal fabrication facility. In most cases, their function is to remove material and produce round parts using the dimensions and tolerances from a drawing.

However, there is another method for achieving axially symmetrical parts without removing or stripping away any metal: it’s called metal spinning. Sometimes referred to as spin forming, metal spinning deforms a flat sheet of metal over a pre-shaped mandrel without cutting or heating the material. And with steel costs on the rise, it makes sense not to waste any of it by turning it into chips.

Metal spinning works with any ductile metal, including carbon steel, aluminum, stainless steel, copper, and even titanium. While the process was once used exclusively for prototyping and low-quantity runs, CNC technology has made it possible to manufacture parts in high quantities.

 

A step-by-step guide to metal spinning

Since metal spinning is a unique process that might not be as well known throughout the metal fabrication community, the following example may help: 

  • A mandrel, machined in the shape of the finished part, is attached to the lathe
  • The metal blank is attached to the mandrel or held in place by the tailstock
  • The mandrel and plate rotate at high speed as the forming tool presses the plate to fit the shape of the mandrel
  • The end is trimmed, if necessary, and the part is complete

 

What are some of the advantages of metal spinning?

Metal spinning offers significant benefits, not the least of which is its ease of use. Because it is a cold-working process requiring no heating of the metal as it is reshaped, it’s simpler and safer than other processes.

Another advantage occurs as the metal is deformed. Metal spinning tends to compress the material, often making the spun metal stronger than it was before. As the metal is exposed to the rotational force of the lathe, the compression increases its tensile strength and provides a high-performance finished product.

Other benefits include:

  • Lower tooling costs than other types of metal shaping
  • Ideal for either prototyping or production parts
  • Single-piece, seamless metal parts are typically stronger and can tolerate a higher pressure
  • Multiple steps in the forming process can  be completed at the same time
  • Shorter lead times
  • Less material waste

 

What are the typical industrial uses for metal spinning?

Metal spinning offers an economical and versatile method for an assortment of commercial and industrial applications, including: 

  • Aerospace and defense components
  • Commercial foodservice equipment: Custom kitchen equipment and cookware for commercial food application made from stainless steel and several other metals. Examples include stainless steel cooking kettles, smoker housings, and housings for high-pressure cookers.
  • Commercial lighting: Working with stainless steel, aluminum, brass, and copper, metal spinning produces light reflectors used in commercial lighting.
  • Sanitation: The metal spinning process creates parts for street and sanitation vehicles, including flanged steel rings for street sweepers and steel ring housings for sewer cleaning equipment.
  • Filtration industry: Components include air filtration cartridges, sleeves, and rings.
  • Gas cylinders and pressure vessels
  • Heavy industrial components for oil, agricultural, and land vehicles: Includes parts for oil drilling equipment, components for livestock feeding, and parts for earthmoving equipment.
  • Musical instruments
  • Medical: Includes fabricated metal products such as medical imaging housings and components used in laboratory equipment.
  • HVAC: Metal spinning is an effective process producing parts with physical properties that can stand up to the extreme conditions of commercial HVAC applications.
  • Automotive: Custom steel wheel rims in various sizes and designs to withstand the most rugged terrains.

 

Are there different types of metal spinning?

Metal spinning lathes typically fall into three broad categories: manual, power-assisted, and automatic.

  • Manual spinning lathes can generally handle a wide range of blanks from 1.0″ up to 72″ in diameter. An experienced human operator applies the forming tool pressure.
  • Power-assisted spinning is a manual process augmented by hydraulic cylinders. It works well for forming stronger metals (stainless steel and alloys) when human power is insufficient to shape the piece. 
  • Automatic spinning employs Computer Numerical Control (CNC) to automate the spinning process. This method is especially effective for precision high-volume parts that demand consistency.

There are also four operations associated with metal spinning. These include:

  • Conventional spinning during which a series of passes complete the formed part. Each of these passes stretches and thins the material.
  • Shear spinning is often used to produce conical and cylindrical shapes accurately. Unlike conventional spinning, the finished part is formed in one pass.
  • Preforms produced through spinning or drawing take the place of a flat blank disc when starting the metal spinning process.
  • Edge treatment refers to the finishing operation on the spun piece. The parts are often trimmed on the lathe to create a straight edge. In some cases, they may be removed and finished on another machine as a secondary operation.
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