How Are Aluminum Baseball Bats Made?

At the start of the 1970s, the Hillerich & Bradsby Co. had reigned for more than a century as the main producer of baseball bats in the United States. Then along came aluminum to challenge wood in the world of bats. The legendary bat manufacturer stepped to the plate, swung for the fences and the results are worthy of its arborous heritage.

Cutting and Ironing

According to thefabricator.com, aluminum tubes 2 to 3 inches in diameter are cut into 24- to 35-inch pieces. Each tube is slipped over a tapered mandrel and forced by hydraulic pressure through a die. The outside diameter of the ironed tube is constant while the inside diameter varies. As a result, a patented Hillerich & Bradsby process controls the thickness of the barrel's wall while reducing that of the tapered portion of the tube--reducing the metal required to form a bat handle.

Swaging

Two dies then rotate around the tube at 850 rpm and apply 5,100 impacts per minute, reducing the diameter of the bat until its desired handle size is achieved. Normally, this rotary "swaging" would shape the tube quickly, and as the wall's diameter decreased, its thickness would increase. To prevent this from occurring, according to thefabricator.com, another patented method uses a mandrel to control the diameter of the inside wall (and subsequent wall thickness) from barrel to bat handle.

Cleaning and Aging

To remove the lubricants of ironing and swaging, each bat is heated to almost 900 degrees for 20 minutes. This, according to thefabricator.com, causes various elements of the alloy to become soluble and dissolve into a molten salt bath. The bat is then immersed into a supersaturated solution that prepares it for "precipitation aging," which is a hardening process. In the process, the bat is kept in a furnace for 12 hours at 300 degrees.

Capping and Polishing

Now that the bat has achieved its shape and degree of hardness, the open end of the barrel must be closed. The bat is spun in a machine at 1,600 to 1,800 rpm at 400 degrees while a forming tool seals and closes the softened metal at the end. The bat is then fed through a machine that rotates and polishes it with various grits to achieve specific-finishing characteristics. Now, according to thefabricator.com, a stage called "shot peening" strengthens the aluminum and adds compressive stresses, plus a final decorative appearance to the bat. Each bat is silkscreen-printed and sealed to lock in dyed colors.

Final Touches

According to thefabricator.com, selected bats are now injected with a polyurethane foam of liquid resin, catalysts and blowing agents. All bats are weighed by electronic scale to meet precise specifications, and handles are cleaned before entering an automatic welding booth for the attachment of knobs. Rubber grips are applied by air pressure while wrap grips are done by hand. Finally, the gleaming new bats are ready for labeling, wrapping and boxing for shipment.