An aluminum bat that is broken in slowly develops thousands of tiny fractures that increase the bat's compression when it makes contact with the ball. This increased barrel compliance, along with enhanced user comfort levels, yields a higher performance than a newly purchased bat. An aluminum bat that has been fully broken in will eventually crack or dent from long-term use. Use your new aluminum bat carefully and under the right conditions to break it in evenly.
Break in the new aluminum bat at a baseball/softball field on days when the temperatures are between 65 and 85 degrees Fahrenheit. Overly cold and hot temperatures make it more likely that uneven wear will be caused.
Ask a friend to pitch the softball to you just as it will be thrown in a game. Harder balls and dimpled batting cage balls cause dents and cracks in an aluminum bat.
Spin the bat in your hands about a quarter turn between each pitch so you are striking the bat in a new location every time. The idea is to cause the aluminum to compress equally all the way around the barrel of the bat so it is actually thinner. Add grip tape to the handle to increase your comfort and control during the swing.
Use the bat in a game situation only after it has been through around 500 impacts with the ball at full speed. By this time, the weight of the bat will feel natural in your hands and the slightly thinner barrel will increase compression to optimize performance.