This Standard specifies requirements for parallel screw threads, associated gauges, and gauging practice, having the Unified thread form and covering the diameter size range No 0 (0.060 in) to 6 in inclusive.The Standard gives information on tolerances, deviations, thread classes, and designations.A supplementary series of Unified threads (UNS) is given in Appendix A for guidance on Unified threads of diameter greater than 6 in, and non-standard diameter/pitch combinations, which may be required for special applications.Appendices give the basis of the tabulated values (Appendix B), examples for calculating the limits of size of untabulated screw threads (Appendix C), notes on the production of external threads (Appendix D), notes on pitch and flank angle errors (Appendix F), notes on the function and checking of gauges (Appendix E), notes on a recommended system for gauging coated threads (Appendix G), notes on the setting of adjustable screw ring gauges (Appendix H), and the limiting dimensions of screw gauges for the more commonly used Unified threads (Appendix I).NOTES:1. Unified screw threads are also known as the ISO inch series screw threads. These screw threads are obsolescent and should not be used in new designs.2. Because of the methods adopted for rounding the tabulated values (see Appendix B), the values for the various parameters given in the tables are to be taken as authoritative for the application of this Standard.3. The information given in Appendix A may also be used for calculating screw thread parameters for diameters greater than 6 in.

Reconfirmed 2017. First published as part of AS B133-1955 (endorsement of BS 1580:1953 without amendment). Revised and redesignated AS B133, Parts 1 and 2-1963 (endorsement of BS 1580:Parts 1 and 2:1962 without amendment). AS B133.3 first published 1963 (endorsement of BS 1580:Part 3:1965 without amendment). AS B121.1 first published 1962 (endorsement of BS 919:Part 1:1960 with amendment). AS B121.4 first published 1965 (endorsement of BS 919:Part 4:1965 without amendment). AS B133, Parts 1 and 2-1963, AS B133.3-1963, AS B121.1-1962 and AS B121.4-1965 revised, amalgamated and redesignated AS 3635-1990.