A ball-peen or ball peinhammer, also known as a machinist's hammer,[1] is a type of peeninghammer used in metalworking. It has two heads, one flat and the other, called the peen, rounded. It is distinguished from a cross-peen hammer, diagonal-peen hammer, point-peen hammer, or chisel-peen hammer by having a hemispherical peen.
Etymology
In the word "ball-peen", peen, sometimes written pein,[2][3][4] probably comes from a North Germanic source; compare dialectal Norwegianpenn (“peen”), Danishpind (“peg”), GermanPinne (“the peen of a hammer”), Old Swedishpæna (“to pound iron with a hammer”).[5]
Uses
Besides peening (surface-hardening by impact), the ball-peen hammer is useful for many tasks, such as striking punches and chisels (usually performed with the flat face of the hammer). The peening face or ball face is useful for rounding off edges of metal pins and fasteners, such as rivets. It can also be used to make gaskets for mating surfaces: a suitable gasket material is held over the surface that needs a gasket, and the operator lightly taps around the edges of the mating surface to perforate the gasket material.[6]
A. Ball-peen hammer B. Straight-peen hammer C. Cross-peen hammerExample of a hard-faced ball-peen hammer
Variants
Variants include the straight-peen, diagonal-peen, and cross-peen hammer. Instead of a ball-shaped head, these hammers have a wedge-shaped head. The straight-peen hammer has a wedge oriented parallel to the hammer's handle. The cross-peen hammer's wedge is oriented perpendicular to the handle.[4] The head of a diagonal-peen hammer, as the name implies, has a wedge set at a 45° angle from the handle; it can be a left angle or a right angle, and some peen hammers have a double diagonal wedge[3] for ergonomic reasons.[7] They are commonly used by blacksmiths during the forging process to deliver blows for forging or to strike other forging tools.
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