Linear shafts are elongated, rod-shaped devices that provide linear or rotary motion for power transmission applications. They are used as axles, pistons, and rollers in heavy machinery. Some linear shafts have axial or radial holes for mounting to support structures. Others are grooved for the placement of snap rings or channeled for keyways. Solid or hollow linear shafts with male or female threads and stepped or chamfered ends are also available. Most linear shafts are made of aluminum, alloy steel, carbon steel, stainless steel, composite materials, or plastics. Alloy steel is harder than carbon steel and provides superior durability. Stainless steel is well-suited for applications in which corrosion resistance is an important consideration. Aluminum linear shafts provide good electrical and thermal conductivity, high reflectivity, and resistance to oxidation. Composite materials are often made of carbon fibers bonded together by resins. They are not as strong as metal shafts, but are lightweight and help reduce energy requirements.