Get a dead-weight hammer (a sand hammer). Stand the bat up on its handle and hammer around the donut in a circle. Hammer it downward towards the handle. Whichever side of the donut is the highest, start hammering that side first and then just keep hammering around.
You possibly mean a MAUL hammer. This is a large heavy hammer, often of 4-8 pounds weight. There is a flat striking face one side and generally a small axe on the opposite side. It's used for pounding spikes and stakes and for splitting logs.