This Standard specifies deviations and limits of sizes for pitch and crest diameters for ISO general purpose metric internal screw threads conforming to JIS B 0205-3 having basic profile according to JIS B 0205-1. Internal screw threads according to this Standard 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 JIS B 0209-1. The fundamental deviations for internal screw threads with a tolerance position AZ have been calculated according to the following formula: ElAZ = + (300 + 20P) where, El 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: ElAX = + (220P - 20) where, El is expressed in micrometres; P is expressed in millimetres. Products made with thread tolerances according to this Standard may show load failure when tested in accordance with JIS B 1052 without adjustment of the other mechanical properties. Internal screw threads with thread tolerances according to this Standard must not be mated with external screw thread having thread tolerances according to JIS B 0209-4 because such combinations will create severe risk of thread stripping.