A ball-peen hammer is also known as an engineer's hammer or a machinist's hammer and may be graded by the weight of the head. It is the mechanic's hammer of choice when making gaskets or driving drift pins.
The ball-peen hammer's crowned, or rounded, edge works metal smoothly without marking it. The ball portion can straighten, soften and expand metal into the desired shape. The other, straighter end of the hammer can be used to strike punches and chisels. A chisel is a steel metal cutter that cuts sheet metal, rivets, bolts and even plaster. Punches mark metal or wood for placement of holes and a ball-peen hammer is used to strike the punch when an automatic punch is not used.