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适用范围：This part of BS 1916 gives guidance on tolerances, limits and fitsfor engineering sizes up to 19.69 in. The recommendations applyparticularly to fits between cylindrical parts, designated as “holes”and “shafts”, in which case the term “size” refers to the diameter ofthe mating parts. The data may also be applied in appropriate cases,by suitable selection of the grades of allowance and tolerances, to fitsbetween other than cylindrical mating parts, in which case the “size”refers to a length, width or other dimension instead of to a diameter.The system described in this British Standard comprises suitablecombinations of 16 grades of tolerance and 21 types of fit for bothhole and shaft, ranging from fits of extreme interference to those ofextreme clearance. All but very exceptional engineering requirementsare covered, from very coarse work to fine gauge manufacture.A selection of fits for general use is given in Figure 4, and furtherguidance on tolerances for shafts and holes for a wide range of fitsis given in Part 2 of this British Standard, but it is intended that aparticular industry or organization extracts and uses those limits whichsuit its own product. A unilateral hole basis system is recommendedbut a full range of holes suitable for use on a shaft basis system,unilateral or bilateral, is also included in the tables.