BS 93:2008

Foreword
1 Scope
2 Normative references
3 Terms and definitions and symbols
4 Profile of British Association (B.A.) screw thread
5 Basic sizes of B.A. threads
6 Tolerance classes and limits of sizes, and tolerances, for B.A
  threads
7 Gauges
Annexes
Annex A (informative) - Basis of sizes of B.A. threads
Annex B (informative) - Bases of allowances and tolerances for B.A
        threads
Annex C (informative) - Effect of errors in pitch and flank angle
        on the effective diameter
Annex D (informative) - Approximate inch equivalents of B.A. thread
        sizes
Bibliography

Describes limits of sizes, and tolerances, for single start parallel screw threads of British Association (B.A.) form.

This British Standard specifies limits of sizes, and tolerances, for single start parallel screw threads of British Association (B.A.) form. It is not applicable to screw threads associated with interference fits, such as those on the “metal ends” of studs and in the corresponding tapped holes. This British Standard specifies the following: basic sizes for B.A. threads, sizes 0B.A. to 16B.A.; limits of size, and tolerances, for close class and normal class external threads of sizes 0B.A. to 10B.A.; limits of size, and tolerances, for normal class external threads of sizes 11B.A. to 16B.A.; limits of size, and tolerances, for a single class of internal threads of sizes 0B.A. to 16B.A.