For extrusion, a bar of metal is forced through a die orifice by a compressive force that is applied to a ram; the extruded piece that emerges has the desired shape and a reduced cross-sectional area.

• A. A bar of metal is cast into a mold
• B. A bar of metal is rolled between rollers
• C. A bar of metal is forced through a die orifice by a ram
• D. A bar of metal is drawn through a tapered bore

Answer: (C)

Extrusion uses a ram to push a bar of metal through a shaped die opening. The material flows plastically and takes on the die’s geometry as it exits, giving the desired shape, with a reduced cross-sectional area because the die opening is smaller than the original bar. This setup produces a continuous profile that matches the die along its length. Other metal-forming methods work differently: casting fills a mold with molten metal to form the shape, rolling deforms the bar between rollers to reduce thickness and change shape, and drawing pulls the work through a tapered bore under tension to reduce its cross-section.