Interchangeable parts are parts that are identical for practical purposes. They are made to specifications that ensure that they are so nearly identical that they will fit into any assembly of the same type. One such part can freely replace another, without any custom fitting, such as filing. This interchangeability allows easy assembly of new devices, and easier repair of existing devices, while minimizing both the time and skill required of the person doing the assembly or repair.
Ford would often use interchangeable parts between car models to save costs, but slowly decreased after it lost market share to Chevrolet
A pulley block for rigging on a sailing ship
A wooden gear from one of Terry's tall case clocks, showing the use of milled teeth.
A file is a tool used to remove fine amounts of material from a workpiece. It is common in woodworking, metalworking, and other similar trade and hobby tasks. Most are hand tools, made of a case hardened steel bar of rectangular, square, triangular, or round cross-section, with one or more surfaces cut with sharp, generally parallel teeth. A narrow, pointed tang is common at one end, to which a handle may be fitted.
Detail of a double-cut flat file showing cutting surfaces on both wide and narrow faces
Relative tooth sizes for smooth, 2nd cut and bastard files
A selection of diamond impregnated files
A selection of riffler files
