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1950 Supplement to Screw-Thread Standards for Federal Services 1944

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1950 Supplement to Screw-Thread Standards for Federal Services 1944 U. S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS 1950 SUPPLEMENT TO SCREW-THREAD STANDARDS FOR FEDERAL SERVICES 1944 1950 Supplement to Handbook H28 (1944) National Bureau of Standards DEC 1 6 1952 78441 QC1 Related Publications .... U51 cop, 2. Screw-Thread Standards for Federal Services, 1944 Screw-thread standards for the Federal Government have been estab¬ lished by the Interdepartmental Screw-Thread Committee of the Army, Navy, Air Force, and Commerce Departments in order to insure the interchangeability of threaded parts. Bolts, nuts, gages, dies, taps, wrenches, and all other items associated with the manufacture of threaded parts have been listed, and definitions of sizes, tolerances, and shapes are fully illustrated by means of drawings and tables. Order NBS Handbook 28 (1944), Screw-Thread Standards for Federal Services, 1944, 274 double-column pages, from the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C. Price ?1.00. Unified Screw-Thread Standards An accord for unification of American, British, and Canadian standard systems of screw threads was signed at the National Bureau of Stand¬ ards on November 18, 1948. This circular gives the proceedings of the meeting, together with detailed illustrations, tables, and numerical data setting forth standards of thread form. In the past, international trade in mechanical equipment of all kinds has been seriously handicapped by the lack of interchangeability of screw-thread parts. The adoption of these unified screw-thread stand¬ ards will remove an important barrier to the exchange of manufactured goods throughout the world. Order NBS Circular 479, Unified Screw-Thread Standards, 27 large pages, illustrated, from the Superintendent of Documents, U. S. Gov¬ ernment Printing Office, Washington 25, D. C. Price 20 cents. UNITED STATES DEPARTMENT OF COMMERCE • ® ° Charles Sawyer, Secretary NATIONAL BUREAU OF STANDARDS • E. U. Condon, Director 1950 SUPPLEMENT TO NATIONAL BUREAU OF STANDARDS HANDBOOK H28 (1944) 1950 SUPPLEMENT TO SCREW-THREAD STANDARDS FOR FEDERAL SERVICES 1944 Prepared by direction of the Interdepartmental Screw-Thread Committee and superseding the Supplement issued June 15, 1949 [Issued March 20, 1951] UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1951 For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C. Price 50 cents Foreword This 1950 Supplement to Handbook H28 (1944), Screw Thread Standards for Federal Services, replaces and augments the Supplement issued June 15, 1949. The former Supplement is reproduced herein with the exceptions of Section I, Appendix 6, and Appendix 9, which are superseded by Section I, Section II, and Section XV, re¬ spect ively, in this supplement. Sections XVI and XVII herein, constitute new mate¬ rial. In order to preserve the topography of the previous Supplement, Sections II, XV, XVI, and XVII follow the Appendices. The approval of these standards by the Federal Departments represented on the Interdepartmental Screw Thread Committee, as indicated on page v, makes them available for application to new designs and for acceptance of bolts, screws, nuts, and other threaded products that conform to these standards. The revision of the Hand¬ book in its entirety will follow later. On November 18, 1948, the Declaration of Accord with respect to the Unification of Screw Threads shown on the opposite page was signed bv representatives of govern¬ ment and industry of Canada, the United Kingdom, and the United States. The publication of the Interdepartmental Screw Thread Committee, which was referred to in the Accord, was entitled, Unified Screw Threads as Recommended by the Interde¬ partmental Screw Thread Committee. The proceedings at which this Accord was signed are recorded in National Bureau of Standards Circular 479, Unified Screw Thread Standards. This 1950 Supplement to Handbook H28 (1944) includes the Unified standards for thread form, for the coarse-thread series in sizes from % inch to 4 inches, inclusive, and for the fine-thread series in sizes from % inch to lb inches, inclusive, as agreed upon at the time the Declaration of Accord was signed. It also includes subsequently agreed upon Unified special threads and American National diameter-pitch combina¬ tions that have not been recognized as Unified standards, but for which allowances and tolerances have been formulated in accordance with the principles of Unified threads. Unified threads are distinguished from others by the inclusion of the letter U in the thread designation. To emphasize the distinction, bold-face type is used throughout the tables. Tables of tolerances, allowances, and other thread data for threads of special diameters, pitches, and lengths of engagement are also included. E. U. Condon, Chairman. n declaration of accord toith respect to the Unification of hereto 'Chreacls is hereby declared that the undersigned, representatives of their Government and Jndustry Bodes, charged coith the dcoclopmcnt of standards for serein threads, 9grcc that the standards for the Unified Screw Threads given in the publications of the Committees of the British Standards 3nstitution, Canadian Standards association, amcrican Standards association and of the interde¬ partmental Screw Thread Committee fulfill all of the basic requirements for general interchangeability of threaded products made in accordance with any of these standards. Ti-he Bodies noted abouc will maintain continuous cooperation in the further dcoclopmcnt and extension of these standards. figned in Washington, 0. C., this jsth day of Jloocmbcr, igt$, at the national Bureau of Standards of the United States. ftlinistru ontradc and Commerce, Bominion of Canada Canadian Standards association 'Tr k . ftlinistru of 3upplu, Bnited Eingdom British Standards institution 'Representative of British industry Bational Bureau of Standards B. 3. Bepartment of Commerce interdepartmental hereto thread Committee amcrican Standards association 'Che amcrican 3ocictu of ftlechanical Engineers ^ocietu of automotive Engineers Sponsors Council of Bnited States and Bnited Eingdom on the Bnification of hereto threads hi APPROVAL BY THE SECRETARIES OF DEFENSE AND COMMERCE AND THE SECRETARIES OF THE DEPARTMENTS OF THE ARMY, NAVY, AND AIR FORCE The accompanying 1950 Supplement to Handbook H28 (1944) on Screw-Thread Standards for Federal Services, submitted by the In¬ terdepartmental Screw Thread Committee, is hereby approved for use by the Departments of Defense and Commerce. Deviations from these standards may be made where the need therefor is shown. Secretary, Department of the Navy Secretary, Department of the Air Force CONTENTS Page Page Foreword_ n Appendix 4. Screw threads of Truncated Whitworth Declaration of Accord- in form_ 35 Approval_ v Appendix 5. Miscellaneous standard thread profiles.. 35 Section I. Introduction_ 1 Appendix 6. Definitions of symbols designating the 2. Personnel of the Committee_ 1 dimensions of taper thread elements.. 35 II. Nomenclature; definitions, and letter sym¬ Appendix 8. References__ 35 bols_ 1 Section II. Nomenclature, definitions, and letter III. American National form of thread_ 1 symbols_ 35 IV. American National thread series_ 7 1. Introductory_ 35 V. Screw threads of special diameters, pitches, 2. Definitions of terms_ 36 and lengths of engagement_ 17 (a) Terms relating to types (d) Table of internal thread minor of screw threads_ 36 diameter tolerances_ 17 (b) Terms relating to size of VI. American Standard pipe threads_ 20 parts_ 36 VII. American National hose coupling and fire¬ (c) Terms relating to geo¬ hose coupling threads_ 24 metrical elements of VIII. Miscellaneous standardized product screw threads_ 36 threads of American National form, or (d) Terms relating to dimen¬ American Standard pipe thread form.. 25 sions of screw threads. 37 1. Gas cylinder valve threads_ 25 (e) Terms relating only to (a) Outlet connections_ 25 taper screw threads. 38 (b) Inlet connections_ 27 3. Letter symbols and abbreviations. 39 X. Acme threads_ 28 (a) Dimensional symbols_ 36 7. Gages for Acme threads_ 28 (b) Identification symbols._ 39 (a) Gage tolerances_ 28 Section XV. Unified thread form and series_ 43 (b) Gages for screw_ 29 1. Introduction_ 43 (c) Gages for nut_ 30 2. The Unified form of thread_ 43 (d) Concentricity_ 30 3. Thread series, symbols, and XI. Wrench-head bolts and nuts, and wrench suggested applications_ 43 openings_ 31 4. Classification and tolerances_ 46 XII. Round unslotted head bolts_ 31 (a) General_ 46 XIII. Machine screws, machine-screw and stove- (b) Screw-thread classes_ 51 bolt nuts and set screws_ 31 5. Method of designating a screw XIV. Socket set screws, socket-head cap screws, thread_ 51 and socket-head shoulder screws_ 31 6. Gages_ 85 Appendix 2. Wire methods of measurement of pitch 7. Use of existing thread gages_ 85 diameter_ 31 XVI. Unified threads of special diameters, 4. General formula for measure¬ pitches, and lengths of engagement-. 85 ments of pitch diameter_ 31 1. Introduction_ 85 5. Measurement of pitch diameter 2. Unified form of thread_ 86 of American National straight 3. Preferred diameters and threads_ 32 pitches_ 86 6. Measurement of pitch diameter 4. Classification and tolerances_ 87 of taper threads_... 32 (a) General_ 87l (1) Two-wire method_ 32 (b) Screw-thread classes_ 8$ (2) Three-wire method_ 33 5. Method of designating_ 92 (3) Four-wire method_ 33 6. Directions for determining limits 7. Measurement of pitch diameter of size of special threads_ 92
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