crocodile squeezer

A crocodile squeezer is a mechanical press with two heavy jaws that grip and compress a ball of puddled iron. The device squeezes out slag, cinder, and trapped gases from the hot metal mass while simultaneously working the mass into a denser, more homogeneous billet ready for rolling or forging. It sits between the puddle furnace and the rolling mill in traditional wrought iron production.

The squeezer takes its name from the shape of its jaws, which open and close like a crocodile's mouth. The fixed lower jaw remains stationary while the upper jaw descends under hydraulic or mechanical force, applying pressure measured in hundreds of tons. The puddled ball, typically weighing 50 to 150 pounds when hot, is positioned on the lower jaw and gripped as the upper jaw closes. Multiple compressions are often needed, with the ball being rotated between passes to ensure even consolidation.

Purpose and operation in the workflow

Puddling produces a heterogeneous mass containing pockets of slag and cinder distributed throughout the metal. The squeezer's primary job is mechanical rather than chemical: it forces these impurities out through the metal's surface and into the crevices where they oxidize and can be removed by subsequent shingling or hammering. At the same time, the sustained pressure welds the metal particles together, raising density and improving strength. The temperature during squeezing must remain above the welding heat of iron, typically 2100 to 2200 degrees Fahrenheit, or the metal will not consolidate properly.

Timing matters significantly. If the ball is allowed to cool below welding temperature, the squeeze will only distort the metal without consolidating it. If squeezed when too hot and plastic, the ball may extrude unpredictably or adhere to the jaws. Experienced workers judge the correct moment by color and handling characteristics. The compressed billet emerging from the squeezer is then passed directly to the rolling mill while still hot, or set aside to cool and be reheated later for further processing.

The crocodile squeezer represents one solution to a fundamental challenge in iron metallurgy: converting the spongy product of the puddling furnace into sound wrought iron. Other methods, such as tilt-hammer consolidation or manual shingling under a trip hammer, served similar purposes but required more labor and offered less control. The squeezer's mechanical consistency made it a standard feature in well-equipped puddling mills through the nineteenth and early twentieth centuries, before electric arc furnaces and modern steelmaking rendered puddling obsolete.