REV. AEROSPACE B STANDARD Issued 1996-10 Revised 2001-08

1 SAE Technical Standards Board Rules provide that: This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user. SAE reviews each technical report at least every five years at which time it may be reaffirmed, Revised , or cancelled. SAE invites your written comments and 2001 Society of Automotive Engineers, rights in PLACE A DOCUMENT ORDER: (724) 776-4970 FAX: (724) 776-0790 SAE WEB ADDRESS: Commonwealth Drive, Warrendale, PA 15096-0001 AEROSPACE AS8879 AScrew Threads - UNJ Profile, InchFSC THDSFOREWORDThis SAE AEROSPACE STANDARD (AS) was generated to provide an alternative to the inactive government specification MIL-S-8879 for the UNJ profile, inch screw basic design profile of the threads in this document; the diameter-pitch combinations and tolerances are based on the unified inch STANDARD .

2 These profiles are not interchangeable with Metric (MJ) or UN profile inch screw threads. However, since the UNJ profile and tolerances set down for AEROSPACE UNJ threads ( inch series) in international STANDARD ISO 3161 and ASME (Class 3) were based onMIL-S-8879, the resultant thread geometry is interchangeable with the thread form in dimensional inspection methods for thread characteristics are outlined in ASME document specifies three systems for verification of thread characteristics to ensure dimensional conformance. These three methods correlate to the methods or application categories in theMIL-S-8879 and AS8879 specification, as shown in Table 1:TABLE 1 MIL-S-8879 AAmendment #1 MIL-S-8879 CAS8879AS8879 Rev. BMethod AASME 21 Method BOTHERTHREADOTHERTHREADASME 22 Method CSAFETYCRITICALTHREADSAFETYCRITICALTHREA DASME 23 SAE AS8879 Revision B- 2 -1.

3 SCOPE:This SAE AEROSPACE STANDARD (AS) specifies the characteristics of the UNJ profile inch series of screw threads, to include a mandatory controlled radius of to at the root of the external thread and with a minor diameter of both external and internal threads increased to provide a basic thread height of in order to accommodate the external thread maximum root radius. The following detailed requirements are included:a. UNJ basic profile and design STANDARD series of diameter-pitch combinations for nominal thread diameters from .060 to STANDARD thread classes and form Formulae for thread dimensions and Method of designating UNJ Acceptance and verification Tables for selected diameter-pitch combinations for AEROSPACE screws, bolts, nuts, shaft and bearing retaining screw threads, fluid fittings, and other component thread Tables for UNJ screw threads limiting dimensions and for UNJ thread dimensions and Purpose:This document specifies the geometric characteristics of the UNJ series threads and the acceptance requirements.

4 In addition, the purpose of this specification is to:a. Define the geometric requirements for a selected series of unified screw Threads, Classes 3A and 3B, from ASME , modified to control the root radius and increase the minor Establish requirements for continuous radius at the root of the external Establish requirements for an increase in the minor diameter of both internal and external threads to accommodate the root Relate acceptance requirements to the intended service application of the threaded Provide default verification requirements if not otherwise Require the use of methods of verification in ASME Encourage the use of new or more efficient methods of manufacture, including on-line or statistical process AS8879 Revision B- 3 Field of Application:The UNJ screw thread is intended for threaded parts and used in weight sensitive applications requiring high fatigue strength, resistance to vibration, and where parts are physical size, and strength sensitive.

5 It is also intended for applications where the net fit at maximum material condition provided by Class 3 threads is Applicable Documents:The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text in this document and the references cited herein, the text in this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been ASME Publications: Available from ASME, 22 Law Drive, Box 2900, Fairfield, NJ inch screw Threads (UN and UNR thread Form)ASME and gaging for unified inch screw ThreadsASME screw thread gaging System for Dimensional Acceptability - inch and Metric screw Threads (UN, UNR, UNJ, M, MJ)ASME Nomenclature, Definitions, and Letter Symbols for screw ThreadsASME Surface Texture (Surface Roughness, Waviness and Lay)3.

6 thread Series:The two series of threads recognized by this specification are the STANDARD UNJ and special UNJ. The use of STANDARD UNJ threads shall be given first consideration in the design of new equipment. Within STANDARD UNJ threads, the use of fine threads shall be given preference to facilitate the maximum usage of a limited number of threads. Terms for characteristics of thread shall be as defined in ASME STANDARD UNJ Series: The STANDARD UNJ series of threads consists of three series with graded pitches (coarse, fine, and extra fine) and the three series with constant pitches (8, 12, and 16 threads per inch ). STANDARD UNJ threads shall be selected from those with diameter-pitch combinations listed in Tables 2 through AS8879 Revision B- 4 Special UNJ Series: The special UNJ series of threads consists of all controlled root radius threads with combinations of diameter and pitch that are not included in the STANDARD UNJ Designations:The threads described herein shall be designated in the following manner indicating the nominal diameter, number of threads per inch , thread series symbol (that is, thread form, controlled root symbol and thread series), thread class including the external "A" or internal "B" thread symbol.

7 Reference to AS8879 shall be made in either the threads designation, a general note, or in a reference STANDARD UNJ thread Designations: Threads selected from the STANDARD UNJ series shall be specified in accordance with Figure Special UNJ thread Designations: The identifying letter "S" shall be included in the thread series symbol to indicate a special thread . Special diameter-pitch combinations developed in accordance with this specification shall be designated as shown in Figure 2:SAE AS8879 Revision B- 5 -FIGURE thread thread Basic thread Data: The basic thread data for threads with STANDARD pitches shall be in accordance with Table STANDARD UNJ thread Data: Threads, in accordance with this specification, shall be within the limits of size specified in Tables 2 through 7, for the diameter-pitch combinations shown herein.

8 Characteristics shall include pitch diameter size, major diameter size, and minor diameter Special UNJ thread Data: Dimensions for threads of special diameter-pitch combinations shall be computed from the formulas in Table External threads: External threads shall be of unified form, in accordance with ASME (Class 3A), altered at the root so that the flanks of the adjacent threads are joined by one continuous smoothly blended curve tangent to the flanks at a thread depth of 9H/16, where H is the height of the sharp V thread . The root radius (radius of curvature) tangent to the flanks shall be between pitch and pitch (see Figures 3 and 5). Internal Threads: The internal threads shall be of the unified form, in accordance with ASME (Class 3B), modified at the minor diameter (truncated to 5H/16) to the values given in Tables 2 through 7 (see Figures 4 and 5).

9 Limits of Size:The specified limits of size are considered exact and are inviolable unless specific exemptions are made. The pitch diameter equivalent of variation in any given element, except pitch diameter shall not exceed of the pitch diameter tolerance. Flank angle equivalents are based on a depth "h" which is equal to 3H/4 (see Figure 3). The deviations in lead and flank angle that are equivalent to of the pitch diameter tolerance and lead and angle variations equal thereto shall be determined in accordance with Appendix AS8879 Revision B- 6 -TABLE 2 - Coarse thread SeriesBasicSizePrimary1 BasicSizeSecondary2 ThdsPerInch3 External thread - UNJC Class 3 AInternal thread - UNJC Class AS8879 Revision B- 7 -TABLE 3 - Fine thread SeriesBasicSizePrimary1 BasicSizeSecondary2 ThdsPerInch3 External thread - UNJF Class 3 AInternal thread - UNJF Class AS8879 Revision B- 8 -TABLE 4 - Extra Fine thread SeriesBasicSizePrimary1 BasicSizeSecondary2 ThdsPerInch3 External thread - UNJEF Class 3 AInternal thread - UNJEF Class AS8879 Revision B- 9 -TABLE 5 - Eight thread SeriesBasicSizePrimary1 BasicSizeSecondary2 External thread - 8 UNJ Class 3 ARoot

10 Radius - thread - 8 UNJ Class AS8879 Revision B- 10 -TABLE 6 - Twelve thread SeriesBasicSizePrimary1 BasicSizeSecondary2 External thread - 12 UNJ Class 3 ARoot Radius - thread - 12 UNJ Class AS8879 Revision B- 11 6 - Twelve thread Series (Continued)BasicSizePrimary1 BasicSizeSecondary2 External thread - 12 UNJ Class 3 ARoot Radius - thread - 12 UNJ Class 3 BMajorDiameterMin3 MajorDiameterMax4 PitchDiameterMin5 PitchDiameterMax6 MinorDiameterMin7 MinorDiameterMax8 MinorDiameterMin9 MinorDiameterMax10 PitchDiameterMin11 PitchDiameterMax12 MajorDiameterMin13 SAE AS8879 Revision B- 12 -TABLE 7 - Sixteen thread SeriesBasicSizePrimary1 BasicSizeSecondary2 External thread - 16 UNJ Class 3 ARoot Radius - thread - 16 UNJ Class AS8879 Revision B- 13 7 - Sixteen thread Series (Continued)BasicSizePrimary1 BasicSizeSecondary2 External thread - 16 UNJ Class 3 ARoot Radius - thread - 16 UNJ Class 3 BMajorDiameterMin3 MajorDiameterMax4 PitchDiameterMin5 PitchDiameterMax6 MinorDiameterMin7 MinorDiameterMax8 MinorDiameterMin9 MinorDiameterMax10 PitchDiameterMin11 PitchDiameterMax12 MajorDiameterMin13 SAE AS8879 Revision B- 14 -TABLE 8 - Basic thread DataThreadsperInchPitchTruncationofInter nalThreadCrestFlatatInternalThreadRootan dExternalThreadCrestHeightofSharpVThread TruncationofInternalThreadRootandExterna lThreadCrestMinimumRootRadiusHeightfromS harp "V"toExternalThreadRootand RadiusHalfAddendumofExternalThreadFlatat InternalThreadCrestnp =1/nH = AS8879 Revision B- 15 -TABLE 8 (Continued)