Upset Forging

Upset forging forms heads and localized thick sections by axially compressing bar or wire, delivering high strength and fast production for axisymmetric parts.

Overview

Upset forging (upset heading) axially compresses bar or wire to increase diameter in a localized zone—most commonly to form bolt, screw, and rivet heads. Material flow is controlled by dies, so grain flow follows the part shape, improving fatigue strength versus machined-from-bar features.

Choose upset forging for high-volume, axisymmetric parts where one end (or a short region) needs to be thicker than the shank. It’s well-suited to fasteners and preforms that will be finished by secondary machining, thread rolling, piercing, or trimming.

Tradeoffs: geometry is constrained by axial symmetry and “upset ratio” limits (risk of buckling/overfill). Tooling cost and lead time are real, so it rarely makes sense for low quantities. Final dimensions are typically near-net but not as tight as machining; plan on controlled flash/trim and add machining stock where tolerances or features demand it.

Common Materials

  • Carbon Steel 1018
  • Alloy Steel 4140
  • Stainless Steel 304
  • Stainless Steel 316
  • Aluminum 6061
  • Copper C110

Tolerances

±0.005"

Applications

  • Hex bolt and screw heads
  • Rivets and pins with headed ends
  • Valve stems and tappets (forged preforms)
  • Studs with flanges or collars
  • Electrical terminals/lugs (headed blanks)
  • Axles/shafts with upset shoulders

When to Choose Upset Forging

Choose upset forging when you need a headed end or localized thick section on bar/wire with high mechanical properties and repeatability at production volumes. It fits parts that are largely axisymmetric and can tolerate near-net dimensions with optional secondary machining. It becomes cost-effective when tooling can be amortized across many pieces and cycle time matters.

vs Open Die Forging

Choose upset forging when the feature is a localized diameter increase (head/shoulder) and you need high throughput from bar or wire. Open die forging fits larger, lower-volume parts where the shape is developed by multiple hits and operator control, not dedicated heading tooling.

vs Closed Die Forging

Choose upset forging when the part is essentially a shank with a head/collar and you want the lowest cost per piece at high volumes. Closed die forging is better for more complex 3D geometries that need full impression dies and controlled flash management across the whole part.

vs Cold Forging

Choose upset forging when the operation is specifically heading/upsetting from bar or wire and the primary geometry is a thickened end region. Cold forging is a broader category; for parts needing multiple cold-forming steps (extrusion, coining, forward/backward forming), a multi-station cold former may be the better fit.

vs Ring Rolling

Choose upset forging when you’re building a head/shoulder on a straight part rather than making a ring. Ring rolling excels at seamless rings with controlled grain flow around the circumference and large diameter-to-thickness ratios that upsetting cannot produce.

Design Considerations

  • Keep the upset region axisymmetric and place thickening close to the end to avoid buckling during upsetting
  • Limit upset ratios (diameter increase and upset length) and ask the forger for allowable reductions based on material and temperature
  • Use generous fillet radii at head-to-shank transitions to improve material flow and die life
  • Specify where machining stock is required and which surfaces are as-forged to avoid tolerance surprises
  • Call out straightness and concentricity requirements explicitly; they often drive secondary straightening or machining
  • Provide raw material form (wire vs bar), starting diameter, and heat-treat condition to tighten quotes and reduce process risk