The fixture, also known as the clamp, is a tool which holds the workpiece or prototype with the machine bed of various equipment precisely at the desired location. It is made for preventing the workpiece from physical inertial movement, deforming or losing tolerance precision when processing.
One of the fixture operation principles is geometry limitation. It is designed for matching the object by taking tolerance and shape into account. Another way is that calculating static friction to overcome inertial force. The second way is more common to use.
A fixture is usually made of metals or woods. A metal fixture and a metal object sometimes use electromagnetic force to achieve the fixing function.
The jig, which pronunciation is originated from Japan, is a tool that guides the cutting or the machining tool. Compared to the fixture, the jig has the function of positioning besides fixing. It uses geometry limitation principle that we can usually see a jig in a block form or cotter form with slope design, guiding an object to enter into a smaller space so that limit the position. For further precision positioning, a jig is sometimes designed an enforcement action to tightly fit datum surface.
Usually, A jig or a fixture is made of common industrial plastics ( Bakelite is one of the most widely used plastics because of its excellent non-conduction, intensity, and high-temperature resistance. ) They generally are only dealt with simple surface finishing such as burr removing, grinding and right angle dealing.
Strictly speaking, it is different between both literally. A jig is for fixing and a fixture is for positioning. But currently, people usually mix them up due to the usage condition and duplicated functions.
Both of two increase production capacity and continuously repeat specific motions more precisely.