James Watt had tried unsuccessfully for several years to obtain accurately bored cylinders for his steam engines, and was forced to use hammered iron, which was out of round and caused leakage past the piston. In 1774 John Wilkinson invented a boring machine in which the shaft that held the cutting tool extended through the cylinder and was supported on both ends, unlike the cantilevered borers then in use. With this machine he was able to bore the cylinder for Boulton & Watt's first commercial engine, and was given an exclusive contract for the provision of cylinders owing to the lower tolerance between the piston and cylinder and the resulting improvement in efficiency by lowering steam losses through the gap. Until this era, advancements in drilling and boring practice had lain only within the application field of gun barrels for firearms and cannon; Wilkinson's achievement was a milestone in the gradual development of boring technology, as its fields of application broadened into engines, pumps, and other industrial uses.