Ball-peen hammer

A ball-peen (also spelled pein) hammer, also known as a machinist's hammer, is a type of peening hammer used in metalworking. 
It is classified from a cross-peen hammer, point-peen hammer, or chisel-peen hammer by having a hemispherical head. Though the process of peening has become rarer in metal fabrication, the ball-peen hammer remains useful for many tasks, such as striking punches and chisels.
it is a very useful tool that has many purposes in the hammer industry