BS 3643-2 specifies the fundamental deviations, tolerances and limits of size for the tolerance classes 4H, 5H, 6H and 7H for internal threads and 4h, 6g and 8g for external threads where
appropriate for:
- a coarse pitch series with the range 1 mm to 68 mm diameter
- a fine pitch series with the range 1 mm to 33 mm diameter
- a constant pitch series with the range 8 mm to 300 mm diameter.
For certain diameter/pitch combinations, the fundamental deviations, tolerances and limits of size for tolerance class 4H for internal threads and tolerance classes 6h and 4g for external threads, primarily for aerospace use, are specified.
BS 3643-2:2007 supersedes BS 3643-2:1981, which is withdrawn.