ASME_B1.21M-1997.pdf

STD.ASME B1.21M-EN6L1997075967005B986B843ASME B1.21M-1997METRICSCREW THREADS:MJ PROFILE(Revision of ANSI B1.21M-1978)A NAMERICANNATIONALSTANDARDCopyright ASME Interationalwithout license from IHSNot for ResalTD.ASME B1.21M-EN6L19970759b7005898904T1Date of Issuance:April 2.1998This Standard will be revised when the Society approves the issuance ofa new edition.There will be no addenda or written interpretations of therequirements of this Standard issued to this edition.ASME is the registered trademark of The American Society of Mechanical Engineers.This code or standard was developed under procedures accredited as meeting the criteria forAmerican National Standards.The Consensus Committee that approved the code or standardwas balanced to assure that individuals from competent and concerned interests have had anopportunity to participate.The proposed code or standard was made available for public reviewand 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 endorseany item,construction,proprietary device.or activity.ASME does not take any position with respect to the validity of any patent rights asserted inconnection with any items mentioned in this document,and does not undertake to insure anyoneutilizing a standard against liability for infringement of any applicable Letters Patent,nor assumesany such liability.Users of a code or standard are expressly advised that the determination ofthe validity of any such patent rights,and the risk of the infringement of such rights,is entirelytheir own responsibility.Participation by federal agency representative(s)or person(s)affiliated with industry is not tobe interpreted as government or industry endorsement of this code or standard.ASME accepts responsibility for only those interpretations issued in accordance with governingASME procedures and policies which preclude the issuance of interpretations by individualvolunteers.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 publisherThe American Society of Mechanical Engineers345 East 47th Street,New York,NY 10017Copyright 1998 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll Rights ReservedPrinted in U.S.A.No reproduction or netwrorking permitted without license from IHSNot for ResaleSTD.ASME B1.21M-EN6L199707596700589891338FOREWORD(This Foreword is not part of ASME B1.21M-1997.)This Metric Screw Thread Standard,MJ Profile,is a hard metric version similar to theUNJ Inch ASME BI.15 and MIL-S-8879 Standards which have a 0.15011P to 0.18042Pcontrolled radius root in the external thread and the interal thread minor diameter truncatedto accommodate the external thread maximum root radius.This metric thread is recommendedfor use in high temperature or high fatigue applications.Tolerance Class 4H5H/4h6h is approximately equivalent to a Class 3A/3B Inch J Threadand is intended for aerospace applications.Tabulated data has been provided for Tolerance Class 4g6g and 4G6G/4G5G for commercialapplications or when the standard reduction for coating or plating provided in this Standardis not adequate for the coating thickness required.Table 6 in this issue has been added to define limiting dimensions for Tolerance Class6g/6H for commercial producers and users of this class.Tolerance Class 6g/6H is intendedfor use only in commercial applications.This metric Standard has as its original basis the work done under the direction of theSAE E21/E25 Metric Thread Panel,which developed and published SAE Aerospace StandardAS 1370.A replica of AS 1370 was ballot circulated in American National StandardsInstitute Committee BI as ANSI B1.21.Since the UNJ inch screw thread is predominantly used in aerospace designs,the aerospaceindustry decided to produce a hard metric version for aerospace metric design.The MJscrew thread project was initiated by SAE Committee E21.which was responsible foraerospace propulsion design standards.At the Committees October 25,1971 mecting.Project E21-122 was established to develop metric screw thread requirements for metricaerospace fasteners and threaded parts.A metric thread panel was organized to include representation from throughout theaerospace industry.Participating organizations included the following:SAE/E21-Aerospace Propulsion Design StandardsSAE/E25-Aerospace Propulsion Utility Parts StandardsAIA/NASC-National Aerospace Standards Committce(airframe)ATA-Air Transport AssociationSBAC-Society of British Aircraft ConstructorsALMA-American Locknut Manufacturers AssociationAPFA-Aerospace Precision Fastener AssociationASD/WPAFB-Aeronautical Systems Division,U.S.Air ForceNAPTC-Naval Air Propulsion Test Center,U.S.NavyLiaison representation from ANSV/OMFSThis Panel took into account the activities of ANSI/OMFS,SBAC,ATA,AECMA,ISO/TC 20/SC 4,and ISO/TC I/SC 5 in order to reflect agreements compatible with internationaland U.S.aerospace metric screw thread requirements,as well as coordinating with ANSI/OMFS requirements.i用a with ASMENo reproduction or networking permitted without license from IHSNot for ResaleSTD.ASME B1.21M-ENGL 1997 0759670 0589892 274Much work was done in developing surveys and drafts which were ballot circulatedthroughout the aerospace industry for resolving the thread design elements and involvedthe following:(a)metric diameter/pitch combinations for aerospace fasteners,(b)metric diameter/pitch combinations for other aerospace parts,(c)thread design form,and(d)thread tolerance class and formulae.After fourteen meetings of the Metric Thread Panel,including special meetings withOMFS and the military,the aerospace industry ballot circulated the AS 1370 MJ MetricScrew Thread Standard for approval.In May 1976,it was approved and published by theSAE Aerospace Council.In addition,two preliminary documents were also published.AS1337.published in March 1974.lists the aerospace diameter/pitch combinations for threadedfasteners.and AS 1338,published in February 1976,documents the MJ profile requirementsand tolerance class.Following the publication of AS 1370.an additional standard.AS1421-listing aerospace diameter/pitch combinations for shaft or bearing retaining screwthreads-was published in August 1976.The International Organization for Standardization Subcommittee for Aerospace Bolts andNuts,ISO/TC 20/SC 4.has accepted the MJ metric thread profile for aerospace metricthreaded fasteners.AS 1370 is serving as the basis for establishing the ISO InternationalStandard for MJ metric screw threads.Upon publication of AS 1370.SAE agreed to submit this Standard to ANSI CommitteeBI for approval as the American National Standard for MJ metric screw threads.ANSIB1.21 was approved by American National Standards Committee BI on February 23.1977.The proposed Standard was submitted by Standards Committee BI to the Secretariat andANSI.It was approved and formally designated an American National Standard on November21,1978.This issue updates the 1978 issue and includes:(a)the addition of Tolerance Class 4G6G and 4G5G/4g6g to be comparable with ASMEB1.15.Unified Inch Screw Threads(UNJ Thread Form).which includes Class 2 UNJThreads:(b)the addition of Tolerance Class 6H/6g to provide a Metric J profile comparable withASME BI.13M,Metric Screw Threads-M Profile,for use in general applications:and(c)changes in rounding procedures which follow the principles of ASME B1.30M.Suggestions for improvement of this Standard are welcome.They should be sent toSecretary.ASME BI Standards Committee,345 East 47th Street,New York,NY 10017.ASME B1.21M-1997 was approved as an American National Standard on December 9.1997.CoyratASMEInmemaionaNot for Resale