Jigs and fixtures are essential for metal machining. In their designs, the sizing of these components of work holding devices requires a great deal of experience and careful judgment. This paper describes an application of loop equations for tolerance allocation in jig and fixture design. The technique makes use of two basic equations, for sizes and for tolerances, to relate all functional dimensions to a functional requirement. This can simplify and facilitate the design of specification limits for jig and fixture components. The implementation of the technique is illustrated through a simple example of a milling fixture.
