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Industries & Professions /
Forge Shop Workers
Forging changes the properties of metals, increasing their strength. For this reason, forge shops produce items that must withstand heavy wear, such as automobile and aircraft parts, drill bits, and hand tools. Forged products come in many sizes, from door keys to the components of massive machinery. The metal used in forgings is often steel, although forgings can be made with aluminum, copper, brass, bronze, and other nonferrous metals (metals containing no iron).
The techniques used in forging items are roughly the same for any metal and any size product. The metal is often, but not always, heated to a high temperature in a furnace until it is workable. It is placed between two metal dies and pounded or squeezed into shape by power hammers or presses, sometimes with tremendous force. Excess metal and rough edges are trimmed or ground away. The forgings may be heat-treated to harden or temper the metal, smoothed, polished, and otherwise finished, then inspected to ensure that they meet required specifications.
The equipment of a forge shop includes various types of hammers, presses, dies, upsetters (presses that produce nails, screws, bolts, and other headed items), and furnaces. The workers also use hand tools such as hammers, tongs, and punches to mold and shape forgings. Products are measured throughout the manufacturing process. Quality control systems, such as statistical process control, include electronic sensors on machines that take measurements at various steps of production. Instruments such as gauges, rules, scales, and calipers are used. Some of the major forge-shop production occupations are described in the following paragraphs.
Hammersmiths operate or direct the operation of power hammers equipped with open dies—flat dies—similar to a blacksmith's hammer. Hammersmiths may head a crew of four or more workers. They draw on their knowledge of forging and the physical properties of metal and follow blueprints, diagrams, and work orders to shape heated metal stock into forgings that meet exact specifications. After determining how the metal is to be positioned under the hammer and selecting the appropriate tools, hammersmiths use rules and squares to align the dies in position and hand tools to bolt the dies onto the ram and anvil of the machine. After the metal is heated in a furnace, the hammersmith determines how much hammer force is needed and instructs the hammer driver, who regulates the action of the machine.
Hammer operators have duties similar to those of hammersmiths. The major difference is that hammer operators forge metal parts with impression—or closed—die hammers rather than open-die hammers. Hammer operators who are highly skilled can turn out very intricate forgings.
Press operators set up and operate power presses that use hydraulic pressure to slowly squeeze metal into desired shapes, rather than pounding the metal with drop hammers or power hammers. They use skills similar to those of hammersmiths and hammer operators.
Upsetters operate another type of closed-die forging machine used to produce headed items, such as bolts and screws. After the dies and other parts of the machine are set up and the metal stock has been heated to the proper temperature, upsetters position the hot metal so that a horizontal ram on the machine squeezes the end of the metal into a cavity, where it expands to the desired shape.
Inspectors examine completed forgings to determine if they meet the requirements set forth in specifications and blueprints. Using measuring instruments such as calipers, gauges, and rules, they check the size and shape of forged parts. They may test strength and hardness with special machines and electronic devices. Internal flaws may be detected using ultrasonic inspection equipment.
Die sinkers are skilled workers who make the impression dies for hammers and presses used in forging. They begin by studying blueprints or drawings, then outline the item to be forged on two matching steel die blocks. They use a variety of machine tools, such as milling machines, electrical discharge machinery, and electrical chemical machinery, to form the impression cavities in the die blocks. The impressions are contoured and finished to specifications with tools such as power grinders, scrapers, and files.
Many different workers may be required for cleaning and finishing forgings. Trimmers operate power presses equipped with trimming dies to remove excess metal from forgings. Grinders remove rough edges and smooth contoured surfaces of forgings and forging dies with a variety of abrasive tools.
Sandblasters or shotblasters clean and polish forgings with blasts of compressed air mixed with abrasives such as sand, grit, or metal shot. Large metal parts are loaded onto racks in an enclosed room and then sprayed with abrasives. Small parts are cleaned in a container with gloved blasters manipulating the piece under a nozzle. Picklers control equipment that cleans the forgings chemically. They remove surface scale by immersing the parts in a series of acid baths and rinses.