Why a splitting maul has a fatter head than an axe
A thinner wedge multiplies force more, so you might expect a log-splitting maul to be razor-slim. It is the opposite. In springy material such as wood, friction grabs a narrow wedge and jams it tight, so the maul's head flares much wider than an axe blade to keep it from getting stuck.
Physically, a wedge is a portable inclined plane and one of the six classic simple machines. Tap its blunt end and it turns that push into forces pressing outward, square to its sloping faces. The trade is distance for strength: the wedge moves a long way while the material it splits or lifts moves only a little, and the force grows to match. Its mechanical advantage equals the slope's length divided by its width, or one over the tangent of the tip angle, so the sharper the point, the greater the gain. Binding sets in once that angle drops below the arctangent of the friction coefficient between wedge and material.
Stone came first. The hand axe, chipped from flint into a two-sided edge, may be the earliest wedge of all. Ancient Egyptian quarrymen drove bronze wedges to break building blocks free, and also used wooden ones that swelled when soaked. Some Indigenous peoples of the Americas split timber with antler wedges to build canoes and houses.
Wedges hide inside many tools. A blade is two inclined planes meeting at an edge, turning a push into two opposing forces that part the material. Knives, ploughs, scissors, axes and chisels all work this way, cutting with less force, less waste and more precision than crushing. Drill bits wrap two sharpened edges around a spinning shaft, and their spiral carries the shavings out. The points of nails and forks are wedges too, after which friction holds the shaft in place.
Other wedges hold still. A gib, long and gently tapered, fine-tunes gaps in machine tools. Wedges secure engine poppet valves and bicycle stems, and an ordinary door wedge works almost entirely through friction between door, wedge and floor.
Source: Wedge
