1、A M E R I C A N N A T I O.N A L.S T A N D A R D 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 ENGINEE
2、RS PUBLISHED BY T H E A M E R I C A N S O C I E T Y OF M E C H A N l C A L E N G I N E E R S United Engineering Center 345 East 47th Street New York,N.Y.10017 REAFFIRMED 2017ANSI B1.9-1973(R1979)25 May 1983 ACCEPTANCE NOTICE The above non-Government document was adopted on 25 May 1983 and is approve
3、d for use by the Federal Agencies.The indicated industry group 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 indu
4、stry groups must obtain copies directly from:The American 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
5、 Adopted:22 October 1973 with Errata,February 1979 Releasing Industry Group:The American Society of Mechanical Engineers NOTICE:The Federal agencies use of this standard is subject to a l l the requirements and limitations of FED-STD-H28/14 Screw-Thread Standards for Federal Services Section 14,Butt
6、ress Screw Threads-7O/45O Flank Angles.NOTICE: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:.Arm
7、y-AR Navy-As Air Force-11 Review 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)No part o
8、f 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 thread was des
9、cribed 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.Formerly each applicati
10、on 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 for this thread.As the
11、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 thread form having a pressure f
12、lank 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 having a 7 deg load flank angle,a 45 de
13、g 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 height of approxi-mately 0.56.In November
14、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 desirable,especially since the minimum height
15、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 height of thread engagement of 0.5.Another Ameri
16、can-British-Canadian conference sponsored by the Combined Production and Re-sources Board was held i q Ottawa,Canada,September-October 1945.Here the British proposal of April 1945,with an alternate design of 0 deg pressure flank angIe and a trailing 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 wa
