This part of BS 1916 gives guidance on tolerances, limits and fits for
large diameters (19.69 in to 125 in).
In many industries, components in large sizes are made to
interchangeable as well as to matched fits. There are many practical
problems, however, in achieving interchangeable manufacture in
large diameters, due mainly to difficulties of measurement.
Clause 4 and Clause 5 in Section 1 discuss the known difficulties which
might be encountered and draw attention to those tolerances and fits
where the greater difficulties might be expected to arise. Section 2 puts
forward tables of tolerances, deviations and limits for shafts and holes.
It is strongly emphasized that these should be regarded as
recommendations intended for trial purposes. They are published in
the expectation that experience in their use will enable them to be
confirmed or modified, and will help to bring to light deficiencies in
measuring techniques.
An explanation of the system to which this standard forms an extension
is contained in BS 1916-1.