BS 3643-1:1981

Foreword
Cooperating organizations
Specification
1 Scope
2 References
3 Basic profile
4 General plan
5 Basic dimensions
6 Tolerances: principles and basic data
7 Tolerances: deviations for constructional threads
Appendix
A Notes for guidance
B Outline guide and examples for calculating limits of
    size of untabulated metric screw threads
Tables
1 Basic profile dimensions
2 Maximum diameters
3 Diameter/pitch combinations
4 Basic dimensions
5 Fundamental deviations for nut threads and bolt
    threads
6 Lengths of thread engagement
7 Minor diameter tolerances of nut thread (TD1)
8 Major diameter tolerance of bolt thread (Td)
9 Pitch diameter tolerance of nut thread (TD2)
10 Pitch diameter tolerance of bolt thread (Td2)
11 Minimum root radii
12 Tolerance classes for nuts
13 Tolerance classes for bolts
14 Deviations
Figures
1 Basic profile of ISO metric thread
2 Basic dimensions
3 Tolerance positions with respect to zero line (basic
    size)
4 Nut threads with tolerance position G
5 Nut threads with tolerance position H
6 Bolt threads with tolerance position e, f and g
7 Bolt threads with tolerance position h
8 Bolt root profile
9 Maximum material profiles for internal and external
    threads

Applies to single-start parallel screw threads having the ISO basic profile for triangular screw threads. Data for diameters from 1.0 mm to 300 mm are tabulated and an appendix gives the information necessary to calculate the limits of size for exceptions to the tabulated data.