Corked bat

In baseball, a corked bat is a specially modified baseball bat that has been filled with cork or other lighter, less dense substances to make the bat lighter. A lighter bat gives a hitter a quicker swing and may improve the hitter's timing. In Major League Baseball, modifying a bat with foreign substances and using it in play is illegal and subject to ejection and further punishment.

To cork a bat, a hole approximately 1/2-inch (12.5 mm) in diameter is drilled down through the thick end of the bat roughly six inches deep. Crushed cork, bouncy ball, sawdust, or other similar material is compacted into the hole and the end is typically patched up with glue and sawdust. However, this weakens the bat's structural integrity and makes it more susceptible to breakage, even more so if the cork is placed beyond roughly six inches into the bat. Corked bats are typically discovered when they break during play.

Using a corked bat in Major League Baseball is in violation of Rule 6.06 (d), which reads in full:

A batter is out for illegal action when:

(d) He uses or attempts to use a bat that, in the umpire's judgment, has been altered or tampered with in such a way to improve the distance factor or cause an unusual reaction on the baseball. This includes, bats that are filled, flat surfaced, nailed, hollowed, grooved or covered with a substance such as paraffin, wax, etc. No advancement on the bases will be allowed and any out or outs made during a play shall stand. In addition to being called out, the player shall be ejected from the game and may be subject to additional penalties as determined by his League Punishment advisor.

While filling a bat with cork makes it lighter, there is no rule that prevents a player from using a lighter, uncorked bat. However, lighter wood bats are shorter than heavier bats.

Since 1970, six players have been caught using corked bats. The following table summarizes these events:

Corked bats were tested in the 2007 season of MythBusters where it was found that the cork was detrimental to the bat's performance.

In addition, former player and Major League manager Phil Garner admitted in January 2010 on a Houston radio station that he used a corked bat against Gaylord Perry and "hit a home run" with it.

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