Aluminum baseball bat

A baseball bat is a smooth wooden or metal club used in the sport of baseball to hit the ball after it is thrown by the pitcher. By regulation it may be no more than 2.75 inches (70 mm) in diameter at the thickest part and no more than 42 inches (1,100 mm) long. Although historically bats approaching 3 pounds (1.4 kg) were swung, today bats of 33 ounces (0.94 kg) are common, topping out at 34 ounces (0.96 kg) to 36 ounces (1.0 kg).

A baseball bat is divided into several regions. The "barrel" is the thick part of the bat, where it is meant to hit the ball. The part of the barrel best for hitting the ball, according to construction and swinging style, is often called the "sweet spot". The end of the barrel is called the "top", "end" or "cap" of the bat. Opposite the cap, the barrel narrows until it meets the "handle". The handle is comparatively thin, so that batters can comfortably grip the bat in their hands. Sometimes, especially on metal bats, the handle is wrapped with a rubber or tape "grip". Finally, below the handle is the "knob" of the bat, a wider piece that keeps the bat from slipping from a batter's hands.

"Lumber" is an often-used slang term for a bat, especially when wielded by a particularly able batter.

The "bat drop" of a bat is its weight, in ounces, minus its length, in inches. For example, a 30-ounce, 33-inch-long bat has a bat drop of minus 3 (30 − 33 = −3). Larger bat drops help to increase swing speed. Bats with smaller drops create more power.

The bat's form has become more refined over time. In the mid-1800s, baseball batters were known to shape or whittle their own bats by hand. This allowed there to be a wide variety in shape, size, and weight. For example, there were flat bats, round bats, short bats, and fat bats. Earlier bats were known to be much heavier and larger than today's regulated ones. During the 19th century, many shapes were experimented with, as well as handle designs. Today, bats are much more uniform in design.

Since the bat regulations were set, there have not been many major design changes in the bats.

Baseball bats are made of either wood, or a metal alloy (typically aluminum). Most wooden bats are made from ash. Other woods include maple, hickory, and bamboo. Hickory has fallen into disfavor over its greater weight, which slows down bat speed, while maple bats gained popularity following the introduction of the first major league sanctioned model in 1997. The first player to use one was Joe Carter of the Toronto Blue Jays.Barry Bonds used maple bats the seasons he broke baseball's single-season home run record in 2001, and the career home run record in 2007. In 2010, the increased tendency of maple bats to shatter has caused Major League Baseball to examine their use, banning some models in minor league play.

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