BS 949-4:1990

This standard BS 949-4:1990 Screwing taps is classified in these ICS categories:

• 25.100.50 Taps and threading dies

This International Standard specifies the manufacturing tolerances on the threaded portion of taps for producing the ISO metric threads of tolerance classes 4H to 8H and 4G to 6G as defined in ISO/R 965-I to III (excluding, consequently, classes 7G and 8G considered as usually produced with ground thread taps).

It is valid for the short taps specified in ISO/R 529 as well as for any other kind of ground thread taps with the same diameters and pitches.

The internal threads produced with those taps are conventionally designated by the simplified denomination of “nut” in agreement with the word used in ISO/R 965 for the general designation of all internal threads.

Annex A and Annex B give, for all threads with coarse and fine pitches, the manufacturing tolerances on the threaded position of taps for the following classes of nuts:

4H and 5H − 6H − 7H and 8H

and	4G and 5G − 6G

Manufacturing tolerances on the threaded portion of taps for producing ISO metric threads of tolerance classes 4H to 8H and 4G to 6G. Valid for short taps specified in ISO/R 529 as well as any other kind of ground thread taps with the same diameters and pitches.