THE NATIONAL BUREAU OF STANDARDS

1 THE NATIONAL BUREAU OF STANDARDS . Functions and Activities The functions of the NATIONAL BUREAU of STANDARDS are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the NATIONAL STANDARDS of measurement and the provision of means and methods for making measurements consistent with these STANDARDS ; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials, devices, and structures; advisory services to government agencies on scientific and technical problems; in- vention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications.

2 The work includes basic and applied research, development, engineering, instrumentation, testing, evaluation, calibration services , and various consultation and information services . Research projects are also performed for other government agencies when the work relates to and supplements the basic program of the BUREAU or when the BUREAU 's unique competence is required. The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover. Publications The results of the BUREAU 's work take the form of either actual equipment and devices or pub- lished papers. These papers appear either in the BUREAU 's own series of publications or in the journals of professional and scientific societies.

3 The BUREAU itself publishes three periodicals available from the Government Printing Office: The Journal of Research, published in four separate sections, presents complete scientific and technical papers; the Technical News Bulletin presents summary and preliminary reports on work in progress; and Basic Radio Propagation Predictions provide data for determining the best frequencies to use for radio communications throughout the world. There are also five series of nonperiodical publications: Monographs, Applied Mathematics Series, Handbooks, Miscellaneous Publications, and Technical Notes. Information on the BUREAU 's publications can be found in NBS Circular 460, Publications of the NATIONAL BUREAU of STANDARDS ($ ) and its Supplement ($ ), available from the Superintendent of Documents, Government Printing Office, Washington 25, UNITED STATES DEPARTMENT OF COMMERCE.

4 J FREDERICK H. MUELLER, Secretary NATIONAL BUREAU CF STANDARDS ,A. V. ASTW, Director NATIONAL BUREAU OF STANDARDS HANDBOOK H28 (195 7). screw - thread STANDARDS . FOR federal services . 1957. PART III. ACME, STUB ACME, AND BUTTRESS THREADS. ROLLED THREADS FOR screw SHELLS OF ELECTRIC LAMP. HOLDERS AND UNASSEMBLED LAMP BASES. MICROSCOPE OBJECTIVE AND NOSEPIECE THREADS. SURVEYING INSTRUMENT MOUNTING THREADS. PHOTOGRAPHIC EQUIPMENT THREADS. ISO METRIC THREADS; MISCELLANEOUS THREADS. CLASS 5 INTERFERENCE-FIT THREADS, TRIAL STANDARD. WRENCH OPENINGS. DTIC QUALITY INSPECTED 3. Amends in part H28 (1944) (and in part its 1950 Supplement). [Issued Oc ober 7, 1960]. *. APPROVAL EX THE SEC FBI ARIES OF DEFENSE AND COMCRCE.

5 The accompanying Handbook H28 (1957), Part III, on screw - thread STANDARDS for federal services , submitted by the Interdepartmental screw thread Committee, is hereby approved for use by the Departments of Defense and Commerce. For the of Commerce Secretary of Defense, HI. Accasion For NTIS CRAM. OTIC TAB D. Unannounced a Justification By Di t button/. Availability Code . Avail and/or Oist Special M. Contents Fags Page Foreword ii SECTION XVIII. Photographic equipment threads. 41. Personnel of the Interdepartmental screw thread 1. Tripod connections l for Committee American cameras; /t . Approval by the Secretaries of Defense and Corn- 20 UNC 1A/1B threads merce in ( ) 41. SECTION XII. Acme threads.

6 1 2. Tripod connections for 1. General and historical 1 European cameras: Y . 2. Specifications for Acme form 16 UNC 1A/1B ( ).. 42. of thread 3. Threads for attaching 3. Standard Acme thread se- mounted lenses to photo- graphic equipment 4. Classification and tolerances, ( ) 42. Acme threads 4 4. Attachment threads for lens 5. Limits of size, Acme threads. 6 accessories ( ) _ 42. 6. thread designations 7 5. Shutter cable release tip and 7. Gages for Acme threads 10 socket with taper (Euro- (a) Gage tolerances 10 pean) thread ( ).. 45. (b) Gages for external 6. Shutter cable release tip threads 10 and socket with straight (c) Gages for internal (American) thread threads 17 ( ) .._.. 45. (d) Concentricity 18 SECTION XIX.

7 Miscellaneous threads. 45. SECTION XIII. Stub n Acme threads 18 1. 60 stub threads 45. 1. r>.eral and historical 18 2. Modified square threads 45. 2. Specifications for Stub Acme 3. Threads for dairy sanitary form of thread 18 fittings ".. 46. 3. Standard Stub Acme thread 4. Glass bottle and jar threads. 46. series 19. 4. Classification and tolerances, Appendix 10. Wrench openings 47. standard Stub Acme threads 19 Appendix 11. Class 5 interference-fit threads, 5. Limits of size, standard Stub Trial American Standard 48. Acme threads 20 1. Introduction 48. 6. thread designations 21 2. Scope 48. 7. Alternative Stub Acme 3. Design and application data 48. threads 22 4. Tables of dimensions, torques, 8.

8 Gages for Stub Acme and interferences 52. threads _ 25. (a) Gage tolerances 25 5. Extension of the standard 52. (b) Gages for external threads 26 Appendix 12. The tightening of threaded fasteners (e) Gagea for iutej'ual to proper tension 52. !.. 27 1. Micrometer method 52. 27 2. "Feel" 53. r- (e) GaKinatoensfonb^.i. 27 3. Torque measurement 53. SECTION XI\ . 'atltffral Buttress threads.,*^.-i. Nat, 27 4. Angular turn of nut method 53. 1I .Historical..*. IV . "i. L . 27 5. Use of special devices for con- 2.^5eneral. p$y_ .. ,. _,. 1. 28 trolling tension 53. 3..Specifications r 28 6. 53. :.'r. 32.. C. i I I II If IT! It ^m ii i ^pn^3i ^ .. _ 33 Appendix 13. Three-wire method of measurement 6. British standard Buttress of pitch diameter of 29 Acme, thread jJ.

9 34 29 Stub Acme, and Buttress SECTION XV. nTeTi Kh St ndard rolled threads threads 54. for screw shells ef electric 1. Acme and Stub Acme 54.., i .lamp-hokjers-and for-awew (a) Single-start external l^eljs of unassembled lamp threads 54. '"bases" ' '1 i. 3-1 (b) Multiple-start external '" 1. Fartfj of 34 threads 55. 2. Tnrfcad series'.. J-,.1. 34 (c) Limitations of three- 3. '.,..' r__:'._~ __ 35 wire measurement of SECTION XV Microscope objective i and nose- external threads 59. piece thrqads, 36AM[). 36 2. Buttress threads 59. 1. Generahand historical 36. 2. Specifications \--- t- 36 3. Bibliography on measurement 38 of pitch diameter by means X-fiaae dilafipaam L. of wires 60. 4. British standard for micro- scope objective and nose- piece threads 38 Appendix 14.]

10 Metric screw - thread STANDARDS 61. SECTION XVII. Surveying instrument mourning 1. ISO thread profiles 61. threads .. - 40 2. Standard series for ISO metric 1. General and historical 40 threads 62. 2. Specifications 40 3. Designations for ISO metric 3. Gage dimensions 40 threads 62. Tables Page Table XII. 1. Basic dimensions, general purpose Acme threads. 2. Table XII. 2. Basic dimensions, centralizing Acme threads 3. Table XII. 3. Acme threads series, basic diameters and thread data 4. Table XII. 4. Tolerances and allowances (minimum clearances) for major and minor diameters, Acme thread series 5. Table XII. 5. Pitch diameter allowances for Acme threads 6. Table XII. 6. Pitch diameter tolerances for Acme screw threads, classes 2G and 2C_ _ _ 7.