Castings and forgings are usually taken to a machine-shop, where the surplus metal and rough parts are removed to make the castings conform to the design of the machine for which they are intended. This process is known as machining. They go next to the fitting shop for the necessary handwork, and finally to the erecting shop where the parts are assembled into a finished machine. The machine is then tested, taken apart, crated, and shipped to the customer; it is again set up by men called erectors.
The parts of a machine are finished to the exact dimensions called for in the blue-print by removing, when necessary, a certain portion called a cut or turning. There is a limit to the speed of tools made from ordinary steel because of the friction and heat generated. If too great a speed is used, the heat may take the temper out of the steel, render it useless, and cause the casting to expand. A mixture of soap and water is used to lubricate the casting and tool, and reduce the heat as much as possible. High-speed steel, which has already been described, has a cutting capacity four or five times that of tool steel and for this reason is used extensively.