A ball-peen ) hammer, also known as a machinist's hammer, is a type of peening hammer used in metal-working. Its steel head is harder than that of a claw hammer, so is less likely to chip on impact. Ball peen hammers are commonly used to drive cold chisels, set rivets, and bend and shape metal. Before the advent of pneumatic rivet guns, ball peen hammers were commonly used for riveting. First the flat head drove the nail through, then the round ball was used to "peen over" the other side of the rivet. Before the advent of pneumatic rivet guns, ball peen hammers were commonly used for riveting. First the flat head drove the nail through, then the round ball was used to "peen over" the other side of the rivet. These hammers were made to last.Wooden handled ball peen pein) hammer. The handle has been nailed in and may not be the original. The metal head has one end shaped into a sphere and the other flat.hammer-ball-peen tool metal-work