tug

In hardrock and coal mining, a tug is a heavy iron hook or shackle point cast or forged directly onto the side of a mine cage, pit tub, or kibble. Its sole purpose is to serve as the attachment point for the hoist rope and tackle assembly that lowers and raises loaded containers from the shaft. Without a tug, there would be no safe, rigid connection between the hauling cable and the cage itself.

The tug must be robust enough to withstand repeated shock loads as the cage jerks into motion, stops suddenly, or encounters resistance from guides along the shaft wall. Cast iron tugs are common in older installations, while modern operations typically use forged steel for greater reliability. The shackle pin passes through the tug's eye, and a block and tackle or direct hoist rope connection is made at this point. Positioning is critical: tugs are usually placed symmetrically on opposite sides of the cage to ensure balanced, level lifting.

Wear and failure modes

The tug experiences constant metal fatigue from the rise and fall cycle, particularly at the junction between the tug body and the cage itself. Corrosion in wet shafts accelerates crack propagation, and impact damage from rope slip or misalignment can split or bend the hook. A broken tug can strand a loaded cage mid-shaft and create serious rescue hazards. Regular inspection of the pin holes and metal around the base is standard mine safety practice.

The term "tug" itself is British and Commonwealth mining vocabulary; American mines more often call this attachment a "bail" or "bridle point." The word likely derives from the pulling action of the hoist rope on the hook. Proper maintenance and periodic load testing of tugs are statutory requirements in jurisdictions with active underground mines.