1、AMERICAN NATIO.NAL. STANDARD Buttress Inch Screw Threads 7y45 Form With 0.6 Pitch Basic Height of Thread Engagement ANSI B1.9 - 1973 REAFFIRMED 1992 FOR CURRENT COMMITTEE PERSONNEL REAFFIRMED 1985 PLEASE SEE ASME MANUAL AS-1 1 SECRE TARIA T THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS PUBLISHED BY T
2、HE AMERICAN SOCIETY OF MECHANlCAL ENGINEERS United Engineering Center 345 East 47th Street New York, N. Y. 10017 ANSI B1.9-1973(R1979) 25 May 1983 ACCEPTANCE NOTICE The above non-Government document was adopted on 25 May 1983 and is approved for use by the Federal Agencies. The indicated industry gr
3、oup has furnished the clearance required by existing regulations. Copies of the document are stocked by the DoD Single Stock Point, Naval Publications and Forms Center, Philadelphia,PA 19120, for issue to DoD activities only. Contractors and industry groups must obtain copies directly from: The Amer
4、ican Society of Mechanical Engineers United Engineering Center, 345 East 47th Street New York, NY 10017 or The American National Standards Institute, 1430 Broadway, New York, NY 10018 Title of Document: Buttress Inch Screw Threads Date of Specific Issue Adopted: 22 October 1973 with Errata, February
5、 1979 Releasing Industry Group: The American Society of Mechanical Engineers NOTICE: The Federal agencies use of this standard is subject to all the requirements and limitations of FED-STD-H28/14 Screw-Thread Standards for Federal Services Section 14, Buttress Screw Threads - 7O/45O Flank Angles. NO
6、TICE: When reaffirmation, amendment, revision, or cancellation of this standard is initially proposed, the industry group responsible for this standard, shall inform the military coordinating activity of the proposed change and request participation. Custodians: Army - AR Navy - As Air Force - 11 Re
7、view Activities: Army - AT, AV, MI Air Force - 15,80,82,99 User Activity: Navy - EC Civil Agency Coordinating Activities: Commerce - NBS DOT - AAF, ACO, FAA, FRA, NHT GSA - FSS, PCD HUD - HCC Justice - FPI NASA - JFK, LRC, MSF USDA - AFS Military Coordinating Activity: DLA - IS (Project THDS-004 1)
8、No part of this document may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permis- sion of the publisher. Incorporates 2/79 Errata Copyright 0 1974 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS Printed in U.S.A. FOREWORD Although the buttress
9、thread was described as early as the March, 1888, Journal of the Franklin In- stitute, it was so little used that its national standardization was not undertaken until after the Combined Conservation Committee in early 1942 reviewed the standardization status of items needed in the war ef- fort. For
10、merly each application of the buttress thread was treated individually and the form it took de- pended on the experience of the designer and the manufacturing equipment available. At the American-British-Canadian conference in New York, in 1943, they agreed that a basic profile should be established
11、 for this thread. As the Military Departments needed buttress and other special types of threads, the War Production Board in February, 1944, arranged with the ASA to establish a General War Committee on Screw Threads. The Interdepartmental Screw Thread Committee (ISTC) agreed to develop a buttress
12、thread form having a pressure flank angle of 7 deg, which closely approaches the static angle of friction for well lubri- cated steel surfaces in contact, and a clearance flank angle of 45 deg. The British agreed to prepare and circulate a draft specification for an asymmetrical buttress thread havi
13、ng a 7 deg load flank angle, a 45 deg clearance flank angle, and a basic height of thread engagement of 0.4 pitch. The 1944 edition of Handbook H28 published the ISTCs recommendation of a basic buttress thread form whch had a crest flat in the nut twice that of the screw, and a thread engagement hei
14、ght of approxi- mately 0.56. In November 1944, the ASA War Subcommittee on Buttress Threads was established and after reviewing the British draft of April 1945, this committee felt that because of the distortion tendency of thn wall tubing, a greater basic height of thread engagement than 0.4 was de
15、sirable, especially since the minimum height of thread engagement is necessarily less than 0.4 by one-half the sum of the allowance and the tolerances on minor diameter of internal thread and major diameter of external thread. Therefore, the July 1945 draft of the War Standard was based on a basic h
16、eight of thread engagement of 0.5. Another American-British-Canadian conference sponsored by the Combined Production and Re- sources Board was held iq Ottawa, Canada, September-October 1945. Here the British proposal of April 1945, with an alternate design of 0 deg pressure flank angIe and a trailin
17、g flank angle of 52 deg, was re- viewed and compared with the American proposal of July 1945. Learning that the British had had con- siderable favorable experience on thin wall tubing with buttress threads having 0.9 basic height of thread . engagement, it was decided that the American standard migh
18、t adopt this basis. Accord was also reached on preferred diameters and pitches, thread dimension tolerances and allowances, and on having each standard include in its appendix an alternate thread of 0 degree pressure flank angle. Further, each country agreed to publish the standard in conformance wi
19、th their respective formats. In April 1946, buttress threads were assigned to Subcommittee No. 3 of the Sectional Committee on the Standardization and Unification of Screw Threads, B1, and the committee membership was enlarged. This committee prepared and circulated in 1948 to members of the B1 comm
20、ittee a draft of a proposed standard based on the British proposal with a basic thread height of 0.4. The comments included so many objections to the shallow height of thread that in 1949 the committee decided to base the next draft on a thread having 0.6 engagement height. The committee also voted
21、not to include in the appendix of the American standard data for a buttress thread having 0 deg pressure flank angle as it was evident that this Was only one of several modifications that might be needed for special applications. The next American-British-Canadian conference was called at the reques
22、t of the Director of Defense Mobilization and held in New York, June 1952. The British Standard 1657: 1950 for Buttress Threads which is based on a thread engagement height of 0.4p and the American draft of September 195 1, based on thread engagement height of 0.6p, were reviewed. It was concluded t
23、hat the applications for buttress threads are so varied that threads with either engagement height (0.4 or 0.6) might be preferred for particular design requirements. It was recommended that the next printing of the British standard and the forthcoming American standard include the essential details
24、 of the other countrys standards in appendixes. ASA B1.9-1953, Buttress Screw Threads, was issued in conformance with this recommendation. . This 1973 Revision of B1.9 is being issued to bring the standard into conformance with present practices. The three classes of threads have been reduced to two
25、-Class 2 (standard grade) and Class 3 (precision grade). Following approval by the Sectional Committee of B1, and the Secretariats, the revised standard was submitted to the American National Standards Institute for approval. This approval was granted on October 22, 1973. iii AMERICAN NATIONAL STAND
26、ARDS COMMITTEE 81 !hndardization and Unifiation of Scmw Threads Organized .June, 1921 Reorganized . February, 1929 SPONSORS: Society of Automotive Engineers The American Society of Mechanical Engineers SCOPE : Nomenclature of screw threads; form of threads; diameter and pitches of screws for various
27、 uses; classification of thread fits, tolerances and allowances for threaded parts; and the gaging of threads. Screw threads for fire hose couplings are not included with- in the scope. 1. C. BU-, Chairnun J. B. L.ry. Vi4.ch.irmrv, W. E. Ban. mtuy D. J. EnunwUi. Arrirmt S8cmt.r MRWACE lNDUSfRlES ASS
28、OCIAnON OF AMERICA. IN. nchnidaDmmir(r NuiawArog#strndrdrtl8 R F. Dwnr, Dcr Iloincs, W-ton 0. M W. ht! lines, should be .used if possible with preference given to the middle one. Basic dimensions for each of the pitches are given in Table 2. 6 TOLERANCES . Tolerances from basic size on external thre
29、ads are applied in a minus direction and on internal threads in a plus direction (see Fig. 2). 6.1 Pitch Diameter Tolerances The following formula is used for determining the pitch diameter product tolerance for external or in- ternal threads: ANSI 81.9-1973 class 2 (standard grade) Pitch Diameter T
30、olerance: + 0.00854 6 PD tolerance = 0.002 + 0.00278 where D = basic major diameter of external thread Le = length of engagement p = pitch of thread (assuming no allowance) When the length of engagement is taken as lop, the formula reduces to: 0.002 + 0.0 173 6 It is to be noted that this formula re
31、lates specifically to Class 2 (standard grade) PD tolerances. Class 3 (precision grade) PD tolerances are two-thirds of Class 2 PD tolerances. Pitch diameter tolerances. based on Table 1 Diameter-Pitch Combinations for 7“/45“ Buttress Threads Major Diameter Range From 0.5 thru 0.75 Over 0.75 thru 1.
32、0 Over 1.0 thru 1.5 Over 1.5 thru 2.5 Over 2.5 thru 4 Over 4 thru 6 Over 6 thru 10 Over 10 thru 16 Over 16 thru 24 Preferred Nominal Major Diameters 0.5,0.625, 0.75 0.875, 1.0 1.25, 1.375 1.5 1.75, 2, 2.25, 2.5 2.75, 3, 3.5, 4 4.5,s. 5.5 6 7,8,9, 10 11, 12,14, 16 1.8, 20, 22, 24 T c I 16 1 6-9 - 16
33、16 16 12 12 1 2a - 12 12 12 - 10 10 1 oa - 10 10 10 10 Threads per Inch Preferred TPI Between Heavy Lines - 2 I .5 1.5 1.25 1.35 - lhreadsa Per Inch, n 1 20 16 12 10 8 a6 5 4 3 2.5 2 1.5 1.25 1 - Pitch, P 2 0.0500 0.0625 0.0833 0.1000 0.1 250 0.1667 0.2000 0.2500 0.3333 0.4000 0.5000 0.6667 0.8000 1
34、 .oooo - - Basic Height of Thread, h = 0.6 3 0.0300 0.0375 0.0500 0.0600 0.0750 0.1000 0.1 200 0.1500 0.2000 0.2400 0.3000 0.4000 0.4800 0.3000 - Height o Sharp V Thread, H= 0.890641 4 0.0445 0.0557 0.0742 0.0891 0.1113 0.1485 0.1781 0.2227 0.2969 0.3563 0.4453 0.5938 0.7 125 0.8906 - Height of Thre
35、ad, k,orh, 1.6627 11 5 0.0331 0.0414 0.0552 0.0663 0.0828 0.1105 0.1325 0.1657 0.2209 0.2651 0.3314 0.44 1 8 0.5302 0.6627 - Table 2 Basic Dimensions for 7/45 Buttress Threads of Preferred Pitches Us U“ = or 1.325421 6 0.0663 0.0828 0.1104 0.1325 0.1657 0.2209 0.2651 0.3314 0.44 18 0.5302 0.6627 0.8
36、837 1.0603 1.3254 - !hh,-2h = !hn-2h= 1.1254% 7 0.0063 0.0078 0.0104 0.01 25 0.0157 0.0209 0.0251 0.0314 0.0418 0.0502 0.0627 0.0836 0.1003 0.1254 - T a For key to designation symbols, see Section 4 bee Section 4. note a CApplies to formulas for major and minor diameter in Section 4 Rootb Radius T M
37、ax r= 0.07 14p 8 0.0036 0.0045 0.0059 0.0071 0.0089 0.01 19 0.0143 0.0178 0.0238 0.0286 0.0357 0.0476 0.0571 0.07 14 - Min r= 0.0357 9 0.001 8 0.0022 0.0030 0.0036 0.0045 0.0060 0.0071 0.0089 0.0119 0.0143 0.0178 0.0238 0.0286 0.0357 - Max 0.0826 10 0.0041 0.0052 0.0069 0.0083 0.0103 0.01 38 0.0165
38、0.0207 0.0275 0.0330 0.041 3 0.0551 0.0661 0.0826 S= - Root Truncation Crest Trun- Min cation. I I I I S= f= D.0413 0.145321 11 0.0073 0.0021 12 0.0026 0.0091 0.0034 0.01 21 0.0041 0.0145 0.0052 0.0182 0.0069 0.0242 0.0083 0.0291 0.0103 0.0363 0.0138 0.0484 0.0165 0.0581 0.0206 0.0727 0.0275 0.0969
39、0.0330 0.1 163 0.0413 0.1453 Width o Flat at Crest, F= 1.163161 13 0.0082 0.0102 0.0136 0.0163 0.0204 0.0272 0.0326 0.0408 0.0544 0.0653 0.081 6 0.1088 0.1305 0.1632 - C 2(5 imin) = 1.808031 14 0.0404 0.0505 0.0673 0.0808 0.1010 0.1347 0.1616 0.2020 0.2693 0.3232 0.4040 0.5387 0.6464 0.8080 - dSee p
40、aragraph 6.1 eSee paragraph 11.1 (c) and 11.2 (b) See paragraph 11.3 :omponent Crests formula d Cage in PD tol. NOT-C( for pitch For e 1.00854IZ000 681000 691000 Z6000 E8000 9L000 PLOOO IL000 69000 L9000 S9000 29000 09000 9SOOO S P E 00001 00080 L9990 oooso OOOPO EEEEO OOSZO 00020 L9910 OSZIO 000 10
41、 EE800 SZ900 OOSOO Z - d 8Vl!d 0 I SZI SI 02 SZ E P S 9 8 01 z1 91 02 I OV3blHl 7VNU31NI CL6L-6 19 ISNV AMERICAN NATIONAL STANDARD BUlTRESS INCH SCREW THREADS ANSI 81.9-1973 Threads, per Inch 1 20 16 12 10 8 6 5 4 3 2.5 2.0 1.5 1.25 1 .o Table 4 Tolerances, Class 3 (Precision Gradel I Basic Maior Di
42、ameter From 0.5 Over 16 Over 10 Over 6 Over 4 Over 2.5 Over 1.5 Over 1.0 Over 0.7 thN 0.7 thN 24 thnr 16 thN 10 thru 6 thnr 4 thN 2.5 thru 1.5 thN 1.0 Pitch, , -1 Tolerance on major diameter of external thread, pitch diameter of external and inted threads, and minor diameter of internal thread 2 3 0
43、.0500 0.0037 0.0625 0.0044 0.0833 0.0040 0.1000 0.1250 0.1667 0.2000 0.2500 0.3333 0.4000 0.5000 0.6667 0.8000 1 .ow0 4 - 0.0042 0.0046 0.0049 5 - 0.0043 0.0048 0.005 1 0.0055 0.0061 this latter formula, for various diameter pitch com- binations are given in Tables 3 and 4. 6.1.1 Functional Size. De
44、viations in lead and flank angle of product threads increase the functional size of an external thread and decrease the functional size of an internal thread by the cumulative effect of the diameter equivalents of these deviations. The func- tional size of all buttress product threads shall not ex-
45、ceed the maximum-material-limit. 6.2 Tolerances on Major Diameter of External Thread and Minor Diameter of Internal Thread Unless otherwise specified, these tolerances should be the same as the pitch diameter tolerance for the class used. 6.3 Tolerances on Minor Diameter of External Thread and Major
46、 Diameter of Internal Thread It will be sufficient in most instances to state only the maximum minor diameter of the external thread and the minimum major diameter of the internal thread without any tolerance. However, the root truncation from a sharp V should not be greater than 0.0826 or less than
47、 0.0413. 6 - 0.0046 0.0050 0.0053 0.0058 0.0064 0.0068 0.0074 7 - 0.0049 0.0053 0.0056 0.0061 0.0067 0.007 1 0.0077 8 - 0.0056 0.0059 0.0064 0.0070 0.0074 0.0080 0.0089 9 - 0.0063 0.0067 0.0074 0.0078 0.0084 0.0093 0.0100 0.0108 10 - 0.0068 0.0072 0.0078 0.0083 0.0089 0.0098 0.0 lo4 0.0113 0.0126 0.
48、0135 11 0.0077 0.0083 0.0088 0.0094 0.0103 0.0109 0.01 18 0.01 30 0.0139 0.0152 6.4 Lead and Flank Angle Deviations for Class 2 The deviations in lead and flank angles may con- sume the entire tolerance zone between maximum and minimum material product limits given in Table 3. 6.5 Diameter Equivalen
49、ts for Variations in Lead ad Flank Angles for Class 3 The combined diameter equivalents of variations in lead (including helix deviations), and flank angle for Class 3, shall not exceed 50 percent of the pitch diameter tolerances given in Table 4 (see Appendix A). 6.6 Tolerances on Taper and Roundner, 6.6.1 class 2 Tolemnces. There are no requirements for taper and roundness for Class 2 buttress screw threads. 6.6.2 Cfass 3 Tolerances. The major and minor di- ameter of Class 3 buttress thread shall not taper or be out of round to the exte
