Baseball was born with a ball in one hand and a stick in the other. Throughout the game's first century, that stick was made of wood. But In the late 1960s--capitalizing on the lightness and durability that helped American-built planes win World War II--aluminum became the bat of choice for nearly every baseball and softball team except those in professional uniforms.
From Forest to Mill
More than 150 years of manufacturing baseball bats have revealed the wood of the white ash to be without peer for its rare blend of strength, lightness, fine grains and flexibility. The ideal ash trees grow on the Pennsylvania-New York state border near streams, rivers and flood plains in clusters that force them to grow straight toward the sunlight. Once felled, a tree is cut into 10-foot x 16-foot logs and hauled to the saw mill where a hydraulic wedge reduces them to near bat-sized 40-inch splits.
Seasoned and Matured
An automatic lathe strips rough edges from the splits to produce billets. Inspectors check their grains again before the billets are shipped to the manufacturer's lumber yard. The "seasoning" process air-dries sap and gum from the billets before they are stacked and allowed to dry for six months to two years. After this maturation process, the billets are weighed and inspected once more for quality.
A Work of Art
The surviving billets are placed on an automatic lathe and carefully shaved into the contours of a baseball bat. Each is sanded, inspected again and sorted by weight. Each billet is carefully hand-tooled, shaved and sanded to meet the precise length and weight requirements of a corporate model bat or that of a prominent major league hitter. The billet is weighed repeatedly, and calipers are used to measure it every 1 to 2 inches. The completed bat is branded with the corporate trademark. Some are stamped with a player's signature, stained or both. All bats are then varnished, packed and shipped.
The Origin of an Aluminum Bat
Aluminum tubes 24 to 35 inches in length and 2 to 3 inches in diameter are slipped over a tapered mandrel and forced through a die to be "ironed." The thickness of the barrel's wall is controlled while that of the tapered portion of the tube is reduced to form a bat handle. Two dies then rotate around the tube at 850 rpm and apply 5,100 impacts per minute, further reducing the handle to its specified size. Rotary "swaging" shapes the tube while a mandrel inside controls the diameter of the inside wall (and subsequent wall thickness) from barrel to bat handle.
Cleaned, Hardened, Polished
Each bat is cleaned from the ironing and swaging by heating to 900 degrees for 20 minutes, dissolving the residue into a molten salt bath. The bat is immersed in a supersaturated solution that prepares it for "precipitation aging," a hardening process that keeps the bat in a 300-degree furnace for 12 hours. The barrel's open end is sealed by a forming tool while the bat is reheated to 400 degrees and spun in a machine at 1,600 to 1,800 rpm. The bat is then fed through a rotating machine that polishes it to specific finishing characteristics.
The Finishing Phase
A process called "shot peening" strengthens the aluminum and adds compressive stresses before each bat is silkscreen-printed and sealed to lock in colors. Some bats are injected with a polyurethane foam of liquid resin, catalysts and blowing agents. All the bats are weighed by electronic scale to meet precise specifications, and handles are cleaned prior to entering an automatic welding booth where knobs are attached. Rubber grips are applied by air pressure, while wrap grips are done by hand.
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