History of the Tennis Racket
The first wooden tennis rackets appeared in the 15th century. Before then, different ball games were played with plain hands, gloved hands or wooden bats. In 1873 Major Walter Clopton Wingfield put together a set of official rules and invented what he called "lawn tennis." Tennis rackets were made of wood until 1965, when the first steel racket was produced, soon followed by the first aluminum racket in 1968. The new materials allowed for bigger heads and as a result easier hitting with more power. The oversized racket----at first not easily accepted by the tennis community---became standard at all levels of play in the 1980s.
As new materials and new racket shapes appeared on the market, the International Tennis Federation defined rules for rackets in 1981. The rules have changed over the years, and the most recent rules from 1997 allow rackets of a maximum total length of 29 inches. The average tennis racket is 27 to 28 inches and weighs 10 to 14 oz. The most common rackets are made from aluminum or composites of graphite, fiberglass, boron, kevlar and other materials. Regardless of the brand, most rackets are produced in large factories in Asia.
Forming the Frame
For aluminum rackets the aluminum is melted and then forced into the shape of the racket frame. Composite rackets are made out of layers of different materials: kevlar, boron, fiberglass or graphite. The layers are put together in a sheet that is then cut in strips. The strips are then wrapped around a hollow flexible tube and placed into a racket-shaped mold. Hot air is pumped into the mold to bond the layers of material together.
Drilling the Holes
The multiple spindles of the production machine drill the holes in the racket simultaneously. Then they put a layer of polymer coating, let it dry completely and repeat the process for several coats. Afterward they smooth out the holes from the sharp edges left from the drilling and apply a brand decal before the final coat.
Tempering of Aluminum Rackets
To receive additional strength, the aluminum rackets go through a process of heating and rapid cooling. They are put in the oven until they are white hot and then rapidly cooled in water. Sometimes, the rackets are immersed in a mild acid solution with an electric current passing through it, which changes the surface of the aluminum and gives the racket a shiny finish.
Stringing
The stringer puts a flexible grommet strip---a plastic strip that contains small tubes that fit in the racket's holes and protect the string from rubbing against the frame---in the groove around the edge of the racket head. The strip also protects the frame from scratches and bangs. Then the stringer puts a protective plastic piece---a yoke---into the base of the racket head. Higher-end rackets will come unstrung, so that players can string them to their preferences. The stringers will string only the lower-end rackets. Afterward they seal the handle with a plastic butt cap, wrap the handle with the padded, adhesive grip and fasten its end safely with the vinyl grip tape.
Inspection
In the final stage of the racket production, inspection workers clean the rackets, inspect them for nicks and marks and measure them to make sure that they fit into the size and weight specifications. They put the aluminum rackets through a stress test to determine if the frame has the proper hardness, and they test the composite rackets for stiffness. The grommets need to be smooth, so they do not break the strings. The grip should be soft and even, and the butt cap should fit snugly. The printing on the frame should be clear. If the racket passes the inspection, the workers place it in a protective cover, package it and send it to the warehouse for distribution.
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