The axle upon which a clock's pinions and wheels are mounted. The arbour carrying the balance or pallets is often called a staff. Before the introduction of economic steel-making methods in the 19th century, clock arbours were usually made from case-hardened wrought iron and subsequently from hardened and tempered steel; but because of the difficulties involved in obtaining and working good-quality steel, early American and Black Forest clocks were often fitted with wooden arbors, steel pins forming the pivots.