ISO International Standard

ISO 5414-1 lays down the dimensions of tool chucks (end mill holders) with clamp screws designed for driving flatted cylindrical shanks in accordance with ISO 3338-2 and specifies the clamp screws used. It also gives the maximum diameter of the chuck nose.

ISO 5414-1 defines two types of drive:

chucks with bores equal to or less than 20 mm intended for driving cylindrical shank tools with a single flat, these tools being provided with either a single or a double cutting part; chucks with bores equal to or more than 25 mm intended for driving cylindrical shank tools with a double flat, these tools being provided with a single cutting part only.