COLD HEADING TOOLING PREPRESS

Cold Heading Fastener Tooling Progression & Blank DXF Guide

Cold heading is a high-speed near-net-shape metal forming process wherein raw coiled wire is sheared to length and axially compressed into fastener heads (bolts, screws, rivets, pins) inside cemented tungsten carbide dies at rates up to 400 parts per minute.

1. The Upset Ratio & Buckling Physics

The volumetric ratio of unsupported wire length to wire diameter $U = L_{\text{upset}} / D_{\text{wire}}$ dictates whether the wire compresses uniformly or buckles sideways. Keeping $U \le 2.25$ per blow ensures axisymmetric radial metal flow without cold shut seams.

2. Engineering Specifications & Tolerances

3. CNC Heading Die Machining & Vector Prepress

• Coning Punch Taper: First-blow coning punches must have a 12° - 15° entry cone DXF profile to capture and pre-gather wire volume.
• Carbide Die Wire Clearance: Wire hole diameter in the main die must provide +0.02mm to +0.04mm clearance above maximum wire tolerance to prevent galling.
• Ejector Pin Pinning: KO pin faces should feature a 0.5mm 45° chamfer to eliminate burrs during high-speed knockout.