1988_2021.pdf

REAFFIRMED 2021Intentionally left blank AN AMERICAN NATIONAL STANDARD STUB ACME SCREW THREADS ASME/ANSI B1.8-1988(REVISION OF ANSI B1.8-1977)The American Society of Mechanical Engineers 345 East 47th Street,New York,N.Y.1001 7 Date of Issuance:April 30,1988 This Standard will be revised when the Society approves the issuance of a new edition.There will.be no addenda or written interpretations of the requirements of this Standard issued to this edition.This code or standard was developed under procedures accredited as meeting the criteria for American National Standards.The Consensus Committee that approved the code or standard was balanced to assure that individuals from competent and concerned interests have had an opportunity to participate.The proposed code or standard was made available for public review and comment which provides an opportunity for additional public input from industry,academia,regulatory agencies,and the public-at-large.ASME does not approve,rate,or endorse any item,construction,proprietary device,or activity.ASME does not take any position with respect to the validity of any patent rights asserted in connection with any items mentioned in this document,and does not undertake to insure anyone utilizing a standard against liability for infringement of any applicable Letters Patent,nor assume any such liability.Users of a code or standard are expressly advised that determination of the validity of any such patent rights,and the risk of infringement of such rights,is entirely their own responsibility.Participation by federal agency representative(s1 or person(s)affiliated with industry is not to be interpreted as government or industry endorsement of this code or standard.ASME accepts responsibility for only those interpretations issued in accordance with governing ASME procedures and policies which preclude the issuance of interpretations by individual volunteers.No part of this document may be reproduced in any form,in an electronic retrieval system or otherwise,without the prior written permission of the publisher.Copyright 0 1988 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A.FOREWORD(This Foreword is not part of ASMElANSl 61.8-1 988.)The Standards Committee on the Standardization and Unification of Screw Threads,B1,was organized in June 1921 with the Society of Automotive Engineers and the American Society of Mechanical Engineers as joint sponsors under the procedures of the American Standards Association(ASA),now the American National Standards Institute(ANSI).This Committee was reorganized in May 1929,and its work was divided among five sub-committees as follows:No.1-Scope and Arrangement of American Standard No.2-Terminology and Form Threads,Except Gages No.3-Special Threads and Twelve Pitch Series,Except Gages No.4-Acme Threads,Except Gages No.5-Screw Thread Gages National standardization of Acme screw threads in the United States began in 1932 when Subcommittee No.4 on Acme Threads of Sectional Committee B1 held its first meeting in New York.A report was presented on the types of Acme threads and the range of sizes and pitches in use in this country.It was prepared by C.W.Bettcher with the assistance of F.L.Woodcock.This report developed into a draft standard.When it was finally approved as an American Standard with the designation ASA B1.3-1941,it contained a section of introduc-tory notes and tables covering general purpose screws and general purpose nuts,basic di-mensions of general purpose Acme threads with special and standard pitches,basic dimensions of 29 deg.stub threads,measurements over three wires for Acme threads,basic dimensions of 60 deg.stub threads,and basic proportions for modified square threads.In December 1942,to meet the war emergency,the National Aircraft Standards Commit-tee of the Aeronautical Chamber of Commerce requested the ASA to consider establishing an American war standard for special Acme screw threads for use in aircraft construction.Recognizing the vital importance of aircraft production to the war effort,the ASA at once initiated this project and organized a special committee to develop the standard.At the London Conference on the unification of screw threads held in the summer of 1944,it was proposed that a war standard on Stub Acme threads also be drawn up.Early in March 1945,therefore,the work on this proposed standard was begun and a draft prepared as a result of the discussion with the British and Canadian experts at the Ottawa Conference in October 1945.This draft was dated March 1946 and was submitted to the ASA War Committee on Acme Threads and the ASA War Committee on Screw Threads in April 1946 for approval by letter ballot.However,a Stub Acme war standard was never issued.In April 1946,the Subcommittees of Standards Committee B1 were reorganized to in-clude the responsibility of the ASA War Committee.Subcommittee No.2 on Acme and Stub Acme Threads revised the March 1946 draft on Stub Acme screw