Abstract: A height-adjustable capping chuck assembly is configured for use with an associated high-speed, automated capping machine for threadingly applying closures to associated containers. The chuck assembly includes a chuck body defining a cavity for receiving a closure to be applied, and a chuck mounting sleeve by which the chuck body is mounted on the associated capping machine. An adjustable interface, preferably in the form of a threaded connection, joins the chuck body to the chuck mounting sleeve so that the height of the chuck body with respect to the associated machine can be selectively varied. A releasable locking mechanism releasably retains the chuck body in the selected orientation with respect to the chuck mounting sleeve, whereby height adjustment can be readily effected without tools, and without replacement of the capping chuck assembly, or other components.