Upset / Upsetting

Upsetting — also called heading — is the cold forming operation in which a portion of a wire blank is compressed axially, causing the metal to flow radially outward and form a larger cross-section. It is the defining operation of fastener manufacturing: the formation of a bolt head, screw head, flange, or any other enlarged feature at the end of a part.

The Basic Principle

A defined length of wire — the head portion — protrudes beyond the face of the die. The punch strikes this protruding length, compressing it between the punch face and the die face. Because the material cannot flow backward (the die contains it) and the wire cannot buckle (if the L/D ratio is controlled), the metal flows outward, filling the head cavity.

The critical constraint is the L/D ratio — the ratio of the unsupported length of wire being upset to its diameter:

• L/D ≤ 2.3 — single blow upset without risk of buckling
• L/D 2.3 to 4.5 — requires a cone preform on the first station to gather material, then a finish upset on the second
• L/D > 4.5 — requires three or more stages

This is why multi-station progressive headers exist: to handle large L/D ratios by progressively gathering and forming material across multiple stations.

Open vs Enclosed Upset

• Open upset: the head material is not confined laterally during forming. Produces a simple disc or domed head. The diameter is determined by the volume of material and the punch geometry.
• Enclosed (trapped) upset: the head cavity is fully enclosed by a die insert. The head shape is fully defined by the cavity — hexagonal heads, flanged heads, or any specific profile. Requires greater force than open upset.

Typical Applications

• Bolt heads (hexagonal, flanged, socket, round)
• Screw heads (pan, countersunk, button)
• Rivet heads
• Flange formations on shafts and pins
• Any geometry requiring a larger diameter at one end of the part

Heading Tonnage

The force required to complete an upset is expressed in heading tonnage (or kilonewtons). It depends on:

• Volume of material being upset
• Material flow stress (hardness and tensile strength of the wire)
• Degree of confinement (open vs enclosed)
• Number of blows

Machine selection must ensure the total heading tonnage across all stations does not exceed the machine’s rated capacity. Manzoni machines range from 70 ton (MA) to 700 ton (MF), covering the full range from small precision fasteners to heavy structural parts.

Relationship to Manzoni Technology

The Manzoni Slow Motion Ram® is particularly valuable during upset tooling setup. By activating slow motion mode, the operator can advance the ram toward the dies at extremely low speed — verifying that punch and die are properly aligned before running at production speed. This is critical with enclosed upset tooling, where a misaligned punch can destroy the die on the first stroke.