Upset Forging

Upset forging axially compresses bar or wire to form enlarged heads, flanges, and steps with excellent grain flow for high-strength, high-volume parts.

Overview

Upset forging, also called upset heading, forms larger diameters on the end or along the length of bar or wire by axial compression in a die. It excels at producing heads, flanges, and stepped sections with dense, oriented grain flow and minimal material waste, typically in one or a few blows.

Use upset forging when you need strong, primarily axisymmetric parts such as bolts, valve heads, and shaft ends at medium to very high volumes. It delivers high throughput and low piece cost once tooling is built. Tradeoffs include significant upfront die and setup cost, geometric limits on how much you can upset per blow, and moderate as-forged tolerances that often require finish machining on critical surfaces. Very complex shapes, deep recesses, or non-axial features are poor fits, and design must respect upset ratios and fillet requirements to avoid cracking and tooling issues.

Common Materials

  • Low carbon steel 1018
  • Alloy steel 4140
  • Stainless steel 304
  • Stainless steel 316
  • Aluminum 6061
  • Brass C360

Tolerances

±0.005" to ±0.015"

Applications

  • Bolt and screw heads
  • Valve heads and poppets
  • Axle and shaft ends with flanges or steps
  • Fastener and rivet blanks
  • Automotive steering and suspension rod ends
  • Gear and pinion blanks with upset hubs

When to Choose Upset Forging

Choose upset forging when your part is mainly axisymmetric, needs a larger diameter section on a bar or wire, and will run in medium to high production volumes. It fits best for parts where strength, grain flow, and material efficiency matter more than very tight as-forged tolerances or highly complex geometry. Use it when you can accept simple forged forms plus secondary machining on only the most critical features.

vs Open Die Forging

Pick upset forging over open die forging when your part is a repetitive, bar-based geometry like heads, flanges, or steps and you want higher production rates. The closed tooling in upset forging controls shape and dimensions better, cutting machining and material waste for standardized parts.

vs Closed Die Forging

Choose upset forging instead of general closed die forging when the main features are axial enlargements or simple steps on a bar or wire. Upset tooling is usually simpler and faster for standard headed or flanged shapes, giving lower part cost at volume if you don’t need complex 3D geometry.

vs Cold Forging

Select hot upset forging over cold forging when section increases are large, material is difficult to cold work, or you need bigger parts with substantial plastic deformation. Hot upset forging reduces forming loads, tooling stresses, and risk of cracking for heavy heads and thick flanges.

vs Ring Rolling

Use upset forging instead of ring rolling when you need a headed or flanged end on a solid bar rather than a seamless ring. Upset forging is more efficient for shafts, fasteners, and stepped bars where you only need localized diameter increases, not full rings or bearing races.

Design Considerations

  • Keep the design primarily axisymmetric and focus features on enlarged heads, flanges, and steps to use standard upset tooling efficiently
  • Limit upset height-to-diameter ratios and check with the forge shop on maximum upset per blow to avoid fold-over and cracking
  • Add generous fillet radii between the upset head and shank to reduce stress concentration and extend die life
  • Provide machining stock on critical sealing or bearing surfaces since as-forged tolerances and surface finish are moderate
  • Avoid deep recesses, side holes, and complex undercuts in the forged form; plan those as secondary machining operations
  • Clearly specify which dimensions are functional and tight-tolerance so the shop can balance die cost, trimming, and machining operations in the quote