Clutch Drums

NETFORM has developed expertise in the area of flowformed drums for use in powertrain applications.

Key product differentiation in this area is through the opportunity to use unique cold forming technology for the production of the preform. This technology can eliminate the need for both heat treatment and laser welding operations. It also allows for part consolidation resulting in the reduction of program capital, tooling, supply-base activities and warranty issues.

Flowformed drums are finished machined in dedicated, automated machining cells.

Product Domain




Technical Information

  • Materials: 1010-1035 & HSLA’s
  • Diameter:  Up to 400mm
  • Max. Spline Length:  Up to 500mm
  • As-Formed Features:  ID Spline, Piston Seal Surfaces
  • Work Hardening:  2-3 x base material
  • Spline Capabilities:
    • Major / Minor ±0.15mm
    • Tooth Space ±0.05mm


Cold forming (also called cold forging or coining is a process where material is transformed into new shapes at room temperate in high-tonnage presses.

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Flowforming is a cold rotary forming process where a rotating metal preform is formed over a tool by (typically) three rollers.

The rollers deform the preform, forcing it against the tool (also known as a mandrel), axially lengthening and radially thinning the material.

The material will take on the reverse profile of the mandrel, allowing the forming of features such as splines and piston seal surfaces.

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The very nature of the cold forming process requires material with highly formable properties.  These properties do not lend themselves easily to machining.  Chip management is particularly challenging due to the machined material not wanting to break during machining.

In addition, the nature of cold forming requires that excess material over the finished components is minimized.  This result in very small depths of cut during machining.

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Case Study

An OEM was preparing to equip its next-generation Heavy Duty pickup trucks with an all-new, high-torque 10-speed transmission.

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