Headrod

Headrod is a term used in several technical disciplines to refer to a short, rigid rod that interfaces with the leading part of a mechanism. It is not a single standardized part; its exact form and function vary by application. In mechanical linkages, a headrod often connects a drive element such as a crank, cam, or piston to a guided member like a slider, valve stem, or rocker, transferring axial force while maintaining alignment.

Designs typically feature a cylindrical body, a built-in shoulder or flange, and a hole or threaded end for fasteners or a bearing sleeve. Materials range from carbon steel to stainless steel or aluminum, chosen for stiffness, wear resistance, and weight. Some headrods include a threaded adjustment section to alter length or pre-load in assemblies.

In valve and actuator assemblies, the headrod can act as the interface that carries the valve stem or actuator rod, sometimes incorporating bushings or seals at the head to reduce wear and leak paths. In hobbyist and model engineering contexts, headrods are used in simple piston machines and clockwork linkages to improve motion transfer and reduce play.

Terminology varies by manufacturer and field, and "headrod" is not universally standardized. Related terms include connecting rod, tie rod, and guide rod, which describe similar but distinct components in other parts of a mechanism.