Metal Spinning 101: A Guide

A Cost-Effective Process for Both Small and Large-Volume Production

The process of metal spinning – also commonly known as “metal turning” or “spin forming” refers to the fundamental fabrication process where a flat metal disc, the blank, is fixed in a spinning lathe to form a hollow part with a circular cross-section. As the blank spins, a roller tool forms it by pressing it against a chuck mandrel, which then duplicates the interior form of the part. The result is a precisely shaped workpiece with a compressed grain structure and a smooth surface, which in many cases may not even require further finishing steps.

Metal spinning is indispensable for producing parts such as roofing, commercial lighting, pots and pans, stainless steel bowls, satellite dishes, bases and lids, and thousands of rounded components in industries across the board. The basic shapes produced by metal spinning include variations of the hemisphere, cone, cylindrical shell, and venturi. Variations on those four basic types are limited only by the designer’s skill and imagination. Spin tooling is inexpensive and versatile and design changes are easily accommodated, making metal spinning a perfect solution for short lead prototyping. 

History of Metal Spinning

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The metal spinning trade is one which dates back to antiquity. The skill was in use as far back as the Ancient Egyptian era when metal spinning was limited to soft metals spun by human power on primitive lathes. The technique saw significant advances with the advent of hydro and steam power in Europe and North America in the 19th Century, and by the early 20th Century the electric motor provided the necessary power and high-speed turning capability. Metal spinning craftsmen were now able to turn out quality workpieces in brass, copper, aluminum, and even stainless and cold-rolled steel.

Traditionally, metal spinning has been associated primarily with low volume production, chiefly due to the requirement for highly skilled human operators in a trade with a rather steep learning curve. While the metal turning process and its machine and tooling setups are quite fundamental, developing the required hand eye-coordination may involve a relatively long period of apprenticeship before the skill is mastered. 

The dawning of the digital age in manufacturing has advanced metal spinning in a way that makes it cost-effective for both prototyping and volume production.

CNC Metal Spinning and Automation Today at Metal Craft

CNC and automatic spin forming machines turn out pieces at tolerances, which exceed even the most skilled manual processes. At Metal Craft Spinning & Stamping, we’ve added automated robots to our CNC production line to enhance accuracy in large-scale orders with the quickest turnaround times. Our state-of-the-art KUKA robot arms enable a savings of 18% in cycle times for unloading tasks while ensuring that our products have no defects. Whether short lead prototyping or large-scale production is required, our versatile custom metal spinning capabilities have a diverse spectrum of applications in industries and markets including:

• Agricultural
• Foodservice lighting
• Marine
• Automotive
• Commercial and industrial roofing 
• Commercial and industrial lighting
• Bearing closures
• Air pollution and ventilation
• Custom display stands
• Funeral Urns
• Industrial vacuum cleaners
• Flag-stand bases
• Fireplace accessories
• Satellite dish manufacturing

At Metal Craft Spinning & Stamping, we’re equipped to take on any job, large or small, providing an economical option for high- and low-volume production and prototype fabrication with a host of advantages.

Metal Spinning Automation

Metal Craft has improved its process by adding robots to the metal spinning CNC production line. These automated robots allow us to complete large scale orders in quick turnaround times, which in turn keeps costs low.

We have employed two KUKA robot arms that have a very high accuracy rate, ensuring our products have no defects and are of the utmost quality in less time. Our robot models enable a savings of up to 18% in cycle times for unloading tasks.

What are the advantages of Automation?

• Fast and greater flexibility
• Powerful and precise
• Ergonomic and safe

Traditional Metal Spinning Processes Step-by-Step

The steps of the process are as follows:

1. The mandrel chuck is mounted to the headstock, and the blank is fixed in place by advancing a follower block fixed to the tailstock of the lathe.
2. A tool rest and pin combine as a support system for the lever arms, a scissor-like apparatus. In this configuration, the arms have sufficient leverage to apply adequate pressure to the blank against a roller or other forming tool.
3. Each movement of the roller across the surface of the blank is called a pass. A series of passes is usually required to form the completed part. Multiple passes are achieved by adjusting the lever arms incrementally as the blank is reduced to its final finished form.

This process can be automated for precision repeatability in volume production with the advanced CNC metal spinning technology available at Metal Craft Spinning & Stamping. Our automated metal spinning machines can turn out complex finished pieces from the blank disc in minutes.

Common Metal Spinning Operations 

Metal spinning is best applied to turn out symmetrical parts with a circular cross-section, but these may later be cut for reassembly in a variety of shapes to create a vast range of new products. After multiple passes have been made the finished piece most frequently has a diameter much smaller than the blank, though the original surface area is retained.

The thickness of the material also changes as the metal approaches its final shape. The metal behaves as if it was soft and malleable as multiple axial strokes are made with a variety of roller tools. The entire lathe operation is completed in a single horizontal setup, taking the piece from blank metal disc to the required design shape, and even removing excess flash on the final step.

The following terms and operations will help to define the metal spinning process:

Preforms for Metal Spinning

Rather than beginning with the flat disc blank for each piece, preforms are already in the shape of cylindrical shells, cones, and more. The preforms themselves are made via spinning or other forming operations such as drawing.

Conventional Spinning

The spinning process frequently requires a series of passes to complete the formed part. As each pass is made the metal is stretched, thinning out the material as a result. Thinning out is typical of the conventional spinning process but it can be minimized when required. 

Shear Spinning

Shear spinning is the variation of conventional metal spinning where the finished part is formed in a single pass. Most commonly, conical and cylindrical shapes can be produced accurately with a precisely specified material thickness.

Edge Treatment

With spun parts, the edges can be finished in many ways to enhance the part function or appearance. Edge treatments can be performed in the spinning process to produce a straight edge, folded edge, or rolled or curled edge. 

Metal Spinning Tools and Machines 

Metal spinning lathes fall into three general categories, each particularly suited for certain applications depending upon the material and dimensions of the workpieces.

• Manual Spinning lathes can accommodate a wide range of blanks from 1.0″ (6.35 mm) up to 72″ (1.8 m) in diameter. The largest finished diameter is 58″ and the smallest is 1.0″. Forming tool pressure is applied by a skilled human operator.
• Power Assisted Spinning is used for forming strong metals such as stainless steel. Hydraulic cylinders provide the additional force required to shape the piece when human power alone is insufficient. 
• Automatic Spinning uses Computer Numerical Control (CNC) or Programmable Numerical Control (PNC) to automate the spinning process. This is especially effective for precision high-volume production. With PNC the first blank is formed with manual spinning while the PNC system records the forming tool movements. In “playback” mode the PNC lathe can repeat the process as many times as required, producing an exact duplicate each time; the operator need only position the blanks in the lathe and initiate the playback cycle.

Metal Spinning Tool Types and Materials

Metal spinning tools are grouped into three general categories, including:

1. Male: The male tool is the most common and duplicates the interior dimensions of the part.
2. Female: Exterior dimensions are duplicated by the female tool, commonly used to form returns and flanges. 
3. Collapsible or Segmented: A collapsible male tool is required to remove the tool when the diameter of the workpiece is reduced while forming. The collapsible tool has a removable core which secures the perimeter forming pieces while turning is in progress. The core can be removed to allow those pieces to be removed when the forming is complete. Collapsible tools require assembly and disassembly for each new piece spun.

Metal spinning tool materials can be made from a variety of materials. Most frequently, spinning tools are fabricated from these three types:

1. Steel: Steel tooling is required to form parts made from stainless steel and other strong metal alloys. Mild steel or tooling steel can be used to fabricate tooling, which can achieve a superior surface finish while still maintaining precise tolerances. Heat treating can also increase the lifecycle of the steel tool.
2. Plastic: When the tool needs more durability to maintain closer tolerances, plastic tooling is an ideal solution. Plastic tools also provide a superior finish compared to wood. 
3. Wood: When exact tolerances or finish aren’t a concern, wood tooling can be a quick and inexpensive option. Wood spinning tools can be fabricated from maple or even fine grain particle board.

Metal Craft’s Specialized Metal Spinning Services

Metal spinning in the past was restricted to soft metals and low volume production runs, but this is no longer the case. Today’s advanced metal turning techniques have opened the door to high-volume production with the most highly durable materials.

That makes custom metal spinning a very cost-effective option for rounded metal parts and products in industries across the board. At Metal Craft Spinning & Stamping, our hand and CNC lathe operations now serve industries including:

• Industrial: We can work with aluminum, cold-rolled steel, and stainless steel, as well as copper and brass to fabricate your industrial projects.
• Architectural: Our custom metal spinning process excels for large architectural pieces suited to your specific needs and price requirements. Complete piece service can include finish and assembly to streamline turnover time.
• Injection Molding: We manufacture stainless steel and cold rolled steel hoppers and fittings, which are essential for injection molding machines.
• Roofing: The roofing industry has been relying on our services since 1969. Today, our automated robots produce roof drains for high volume orders with short lead times. 
• Commercial Lighting: Our experience with these aluminum products also goes back to 1969 and today we are experts in the manufacturing of lighting reflectors. Plating, metalizing, and anodizing services are also available. 
• HVAC: Indoor and outdoor ventilation systems require parts with the durability of cold rolled steel, aluminum, and stainless steel, especially in the commercial HVAC sector where extreme conditions are the rule. We combine CNC and hand lathes with our metal stamping capabilities to complete both high and low volume orders with minimal lead times.
• Sanitation: High traffic areas and public spaces often require large garbage can lids to optimize public sanitation. We can manufacture lids and bases in a wide range of sizes and materials, most commonly stainless or cold rolled steel. 

We also have the capability to provide custom designed pieces for prototyping and low volume special orders as needed. Our engineering department can work with you to design a prototype to ensure that you achieve the project goals you’ve set. We can produce a large selection of shapes including: 

• Dished
• Domed
• Domed with flange
• Flanged
• Flanged and flued
• Flanged, dished, and flued
• Hemisphere
• Semi-elliptical
• Trumpet

If you don’t see the basic shape you have in mind for your part or product in the list above, we have the engineering, design, and tooling expertise to make your custom shape reality, and at the precision tolerances, you require. 

About Metal Craft Spinning and Stamping

Established in 1964 and incorporated in 1969, Metal Craft Spinning &Stamping is a family-owned business now into the fourth generation, continuing a hard-earned legacy of quality service and on-time delivery.

Our metal spinning department has mastered the ancient art and we’ve stayed on the leading edge of the industry with state-of-the-art CNC machines, hydraulic presses, and hydroforming machines which allow us to produce thousands of quality parts and products for our hundreds of loyal customers across North America. When you’re ready to put our nearly 50 years of experience to work for you don’t hesitate to contact us.