Drills

Fastener assembly tool standards cover the tools, and their variable parts, that handle the fasteners during their installation. Given the variability within screwdrivers, starting from whether they are machine or hand operated, and continuing down all the way to the bits that actually make contact with the fastener, standardization promotes interchangeability between tools and parts of different manufacturers, and fasteners of yet a different manufacturer. These standards are related to the specifications of drills and their corresponding tools.

ISO 3438:2013 specifies the dimensions of subland twist drills with Morse taper shanks and cylindrical shanks for holes prior to tapping screw threads. The drills are designed to produce holes prior to tapping metric threads (coarse pitch series) over a selected range of: M8 to M30 for subland twist drills with Morse taper shanks; M3 to M14 for subland twist drills with cylindrical shanks. ISO 3438:2013 complements ISO 2306.

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ISO 2306:1972

Drills for use prior to tapping screw threads

Specifies the sizes of these drills for ISO metric threads (tables 1 and 2). ISO inch threads (tables 3 and 4) and pipe threads (tables 5 and 6). Applies to screw threads of normal length of engagement, the drill diamter being approximately equal to the nominal diameter of the thread minus the pitch. The sizes (except for those sizes indicated by an asterisk) have been selected from ISO 235 and are to be used in the future.