This guide is concerned with explaining the system of tolerances and fits contained in the British Standard No 4500 Part 1 and how to use this system. This is a national standard which embodies the international standard No R286.

Note that the numbers in parentheses refer to the ‘List of Definitions” and the Introduction refers to these and to Figures 1 and 2.

Reference is made throughout to the application of tolerances to “shafts” and “holes” and an impression is often created that the system of tolerances described in BS 4500 is suitable only for use with circular features (1). This is not the case and the system can be applied to features having parallel planes. Common examples of such use are the applications to bar stock of square, rectangular and hexagonal section and to keyways and splines.

[Description and screenshot taken from the SEED Curriculum for Engineering Design page for this guide. (c) The Design Society used under the terms of their (CC BY-NC-SA 3.0) license.]