This British Standard gives guidance on the selection of fits given
in BS 1916-1.
The recommendations apply, in particular, to fits between cylindrical
parts, designated as “holes” and “shafts”, in which case the term “size”
refers to the diameter of the mating parts. The recommendations are
also applicable to parts other than cylindrical, in which case the term
“size” refers to a length, width or other dimension.
Tables of preferred sizes are included to avoid the indiscriminate
selection of dimensions, and their use is strongly recommended.