Sheaves are grooved wheels or pulleys used with rope or chain to change the direction and point of application of pulling force. There are many different types of products. Often, suppliers categorize sheaves by materials of construction. For example, some sheave manufacturers carry cast iron, machined steel, or stamped steel sheaves. Cast iron sheaves can provide from 30,000 to 65,000 pounds of tensile strength and are designed to withstand heavy side-loads. Belt slippage is reduced to maximize power transmission at full speed. Steel sheaves are lighter than cast iron sheaves, but not as strong. Products without rivets or spot welds provide better strength, concentricity, durability and run-out control than stamped steel shaves. Machined steel sheaves are impact-resistant and made of bar stock materials. Sheave suppliers that categorize products by features or functions may provide V-ribbed sheaves with smaller belt and groove sections. These products provide smoother and quieter operation than other types of sheaves, and are designed to maintain surface contact with the belt in order to maximize power transmission.