This part of ISO 965 specifies deviations and limits of sizes for pitch and crest diameters for ISO general purpose metric internal screw threads conforming to ISO 262 having basic profile according to ISO 68-1. Internal screw threads according to this part of ISO 965 are intended to mate with external screw threads with maximum size of tolerance position h before hot-dip galvanizing. The limits of sizes for the tolerance quality specified are derived from tolerances specified in ISO 965-1. The fundamental deviations for internal screw threads with a tolerance position AZ have been calculated according to the following formula: EIAZ = + (300 + 20P) where EI is expressed in micrometres; P is expressed in millimetres. The fundamental deviations for internal screw threads with a tolerance position AX have been calculated according to the following formula: EIAX = + (220P - 20) where EI is expressed in micrometres; P is expressed in millimetres. Products made with thread tolerances according to this part of ISO 965 may show load failure when tested in accordance with ISO 898-2 without adjustment of the other mechanical properties. Internal screw threads with thread tolerances according to this part of ISO 965 must not be mated with external screw threads having thread tolerances according to ISO 965-4 because such combinations will create severe risk of thread stripping. NOTE Internal screw threads with tolerance class 6AZ are primarily intended to mate with external screw threads centrifuged after hot-dip galvanizing. Internal screw threads with tolerance class 6AX are primarily intended to mate with hot-dip galvanized external screw threads with heavy coating not centrifuged.