Some people refer to ball peen hammers as engineers’ hammers or machinists’ hammers. This is because a ball-peen hammer is a great tool for working with metal sheets. People use ball peens for all kinds of uses, including things like shaping material for fabrication, hitting punches and chisels, and manufacturing knife blades and swords. However, the original use of ball peens was to peen the metal parts together to make the joints more flexible to work with. Later people started using them for things like expanding copper roves, light rivets, and for setting rivets.