BS 949-4:1990, EN 22857:1989,ISO 2857:1973

Screwing taps. Specification for metric ground thread taps: manufacturing tolerances|Taps (threading), Threading tools, Cutting tools, ISO metric threads, Hand tools, Dimensions, Marking, Dimensional tolerances, Thread pitch, Grades (quality) Click the banner to get it at ONLY: GBP116.00