strickle

A strickle is a rigid finishing tool drawn across the surface of a sand or loam mold to create a smooth, uniform contour and remove excess material. In foundry work, it serves as the final shaping instrument after the mold cavity has been roughed out, and it works in tandem with pattern withdrawal to achieve the dimensional accuracy required for casting. The tool typically has one beveled edge, one flat edge, and sometimes a curved edge, allowing the founder to work multiple surfaces without stopping to change tools.

The strickle's construction varies by application. Foundry strickles are usually made from wood, steel, or brass, with the choice depending on the mold material and the surface finish required. Wooden strickles, often made from oak or hickory, are preferred for use on damp sand because they do not cause the sand to stick; steel strickles are harder and hold their edge longer but can cause tearing on wet or sticky molds. The beveled edge typically sits at 45 degrees, though some specialized strickles are cut to match specific molding profiles.

Working principle and technique

The strickle is drawn toward the operator with light, consistent pressure, following the line of the mold wall or the parting plane. On large molds, the strickle is sometimes guided along a straight edge or strike board to ensure flatness across the parting surface. On curved surfaces, the tool's shape must match the intended contour of the casting cavity. The friction between the strickle and the mold surface compacts the sand slightly and seals minor irregularities, which improves the surface finish of the finished casting and reduces the need for fettling afterward.

Common defects result from incorrect strickle angles, dull edges, or working the mold when the sand moisture is too high or too low. A dull strickle tends to drag and crumble the mold edge rather than cut cleanly, while excessive moisture causes the sand to stick to the tool. The term itself likely derives from the verb "to strike," reflecting the action of drawing the tool in a single deliberate stroke, though in modern usage the noun has narrowed to describe the tool rather than the motion.

The strickle occupies a specific place in the hierarchy of foundry hand tools, sitting between the molding board and the strike board. It differs from a trowel or palette in that it is rigid and beveled rather than flexible, and it differs from a slick or smoother in that it is designed for material removal as well as surface closure. In core-making, strickles are used to dress the core after it has been rammed and stripped from its core box, ensuring that the core dimensions fall within casting tolerances.