peen

In the world of tools, the "peen" is a bit of a specialist. While a typical claw hammer is made for driving and pulling nails, a peen hammer has a special end designed for metalwork. Usually, one side of the hammer head is flat for striking, while the other side is rounded, pointed, or wedge-shaped. Metalworkers and mechanics use this side to stretch, spread, or shape metal with care. If you've ever seen a ball-peen hammer, that rounded end is the "peen." It is useful for flattening rivets or smoothing curves in a piece of steel, acting more like a sculptor's tool than a blunt construction tool.

The term "peen" refers to the shaped end of a hammer head opposite the striking face, and by extension, to hammers that have this kind of end. It is a word deeply rooted in the history of blacksmithing and industrial fabrication. Unlike a standard hammer meant to drive an object into a surface, the peen is designed to shape the metal itself through a process known as "peening."

When a craftsman strikes metal with the peen, they are typically trying to expand the material in a specific direction or strengthen it. The most common variety is the ball-peen hammer, which has a hemispherical end used to "set" rivets, making them permanent and flush. There are also cross-peen and straight-peen hammers; their wedge-shaped ends allow a smith to "draw out" or lengthen metal in one direction without widening it in the other.

Beyond its use as a noun, "peen" is also a common verb. To peen a surface is to work it with these specialized strikes, often to relieve internal stress in a weld or to create a decorative, dimpled texture on handmade jewelry and armor. While you might not find one in a basic household kit, the peen remains an essential tool for farriers, machinists, and artists who need to bend metal to their will with absolute control.