Specifies limits of size for tapped holes to accomodate wire thread inserts to provide ISO metric thread sizes from M1.6 (1. 6 mm diameter) to M39 (39 mm diameter) inclusive.Cross References:BS 919:Part 3BS 949:Part 1BS 1044:Part 1BS 3643:Part 1BS 3643:Part 2BS 4500:Section 1.2