Wedge (mechanical device).html



Wedge
Wood splitting wedge
Classification	Hand tool
Used with	Sledgehammer
Related	Chisel Splitting maul Axe

A wedge is a triangular shaped tool, a compound and portable inclined plane, and one of the six classical simple machines. It can be used to separate two objects, or portions of objects, lift an object, or hold an object in place. It operates by converting a force applied to the wide end into forces perpendicular to the inclined surfaces. The mechanical advantage of a wedge depends on the ratio of its length to its thickness. Where a short wedge with a wide angle does the job faster, it requires more force than a long wedge with a smaller angle.

History

The origin of the wedge is unknown, likely because it has been in use for over 9000 years. In ancient Egyptian quarrys, bronze wedges were used to break away blocks of stone used in construction. Wooden wedges, that swelled after being saturated with water, were also used. Some indigenous peoples of the Americas used antler wedges for splitting and working wood to make canoes, dwellings and other objects.

Examples for lifting and separating

Wedges can be used to lift heavy objects, separating them from the surface they rest on. They can also be used to separate objects, such as blocks of cut stone. Splitting mauls and splitting wedges are used to split wood along the grain. A narrow wedge with a relatively long taper used to finely adjust the distance between objects is called a shim, and is commonly used in carpentry.

Examples for holding fast

An insect nest is wedged in between two stones to hold it in place.

Wedges can also be used to hold objects in place, such as engine parts (poppet valves), bicycle parts (stems and eccentric bottom brackets), and doors.

A wedge-type door stop (door wedge) functions largely because of the friction generated between the bottom of the door and the wedge, and the wedge and the floor (or other surface).

The tips of forks and nails are also wedges, as they split and separate the surfaces into which they are pushed or driven.

Mechanical advantage

The downwards force on the wedge produces a horizontal force in the object

The mechanical advantage of a wedge is the length of the sloping side of the wedge divided by the width of the thick end of the wedge. Therefore the formula for a wedge is:

In other words, divide the length of the wedge by its width at the thickest edge.

The more acute the angle of the wedge, the more mechanical advantage it will have.

Despite this, one reason that many splitting wedges have a wide angle is that an elastic material, such as wood, will bind a narrow wedge more readily than a wide wedge. This is why splitting mauls have a much larger angle than an axe.

See also

• Axe
• Inclined Plane
• Screw
• Splitting maul

External links

• (Mechanics of) wedges and screws

Wikimedia Commons has media related to: Wedges