Baseball bats are made of either wood or aluminum. You'll see aluminum bats in youth leagues or in casual backyard games but Major League Baseball only allows bats made of wood. Aluminum bats are lighter than wooden ones, don't break and allow players to hit the ball farther and faster. Players in the major leagues are expected to have so much speed and power that they don't need the extra help.
Major League Baseball allows bats made out of one of six different types of wood: white ash, sugar maple, true hickory, yellow birch, red oak and Japanese ash. The vast majority of bats are made of either white ash or sugar maple [source: Roberts].
To make a classic Louisville Slugger, start with a white ash tree that is at least 50 years old. The wood used comes from special forests in New York and Pennsylvania. After harvest, the wood dries for six to eight months to a certain moisture level [source: Exploratorium].
The wood is then milled into round 37-inch (94-centimeter) cylinders called billets. When they arrive at the factory, they are put on a tracer lathe using a metal template that is set to the specifications of the baseball player. The Louisville Slugger logo is fire-branded on the flat of the wood's grain where the bat is weakest. A player must swing with the label up or down so he can hit the ball with the edge of the wood's grain which lessens the chance of the bat breaking. The bats are then sanded and dipped in a varnish that gives them a protective coat [source: Exploratorium].
Though the wooden bat seems more All-American, about 95 percent of the bats used in the U.S. are made of aluminum [source: Cole and Lundin].To make an aluminum bat, start with a simple aluminum tube 24 to 35 inches (61 to 89 centimeters) long and 2 to 3 inches (5 to 7.6 centimeters) in diameter. The tube goes through a process designed to thin, stretch and taper the tube walls and also create a handle. Then the tube is then treated with very high heat to remove lubricants and form grains to make it a harder material. At this point it looks like a bat but the ends of the tube are still open. Another machine spins the tube at high heat while a tool forces the softened ends to close over [source: Cole and Lundin].
Finally, the bat is polished and silkscreened with graphics and a knob is welded on to the handle. A grip, either rubber or wrap, is applied to the handle, and a label and a protective film are applied to the bat itself [source: Cole and Lundin].