Batter Throws His Bat
If a whole bat is thrown into fair or foul territory and interferes with a defensive player attempting to make a play, interference shall be called, whether intentional or not. The batter is called out.
If a bat breaks and part of it is in fair territory and is hit by a batted ball or part of it hits a runner or fielder, play shall continue and no interference is called. If a batted ball hits part of a broken bat in foul territory, it is a foul ball.
Sometimes a batter will throw his bat at a pitch during a hit-and-run and lose his grip on the bat. This is a dangerous situation and should be discouraged. If the umpire determines that the bat is thrown intentionally and it interferes with a fielder making a play, two outs could be called.