Metal Spinning

• Simple setup and quick changeover add up to short lead times for new parts
• Design changes with minimum expense
• Superior tensile strength within the finished material
• Dimensional stability with precise tolerances to 1000ths of an inch or 100ths of a millimeter
• Refined and strengthened grain structure
• High integrity and reliability for structural parts

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 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 like bronze spun by human power on primitive lathes. The hand spinning 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, titanium 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.

In the basic set-up for a horizontal spinning lathe the tool (mandrel chuck) is mounted to the headstock of the lathe. A follower block (tail block) is mounted to the tailstock. A circular blank is then clamped to the tool by advancing the follower. The tool rest and pin provide a support system for the lever arms, a scissor-like apparatus. The lever arms apply pressure to the blank via a roller or other forming tool. The movement of the roller across the blank is called a pass.

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

• Male: The male tool is the most common and duplicates the interior dimensions of the part.
• Female: Exterior dimensions are duplicated by the female tool, commonly used to form returns and flanges.
• Collapsible or Segmented: 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:

• 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.
• 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.
• 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.