1997_2018.pdf

REAFFIRMED 2018Intentionally left blank The American Society of Mechanical Engineers A N A M E R I C A N N A T I O N A L S T A N D A R D METRIC SCREW THREADS I I M J PROFllE ASME B1.21 M-1 NU7(Revision of A N S I B1.21 M-1178)Date of Issuance:April 2,1998 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.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 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 assumes any such liability.Users of a code or standard are expressly advised that the determination of the validity of any such patent rights,and the risk of the infringement of such rights,is entirely their own responsibility.Participation by federal agency representative(s)or person(s)affiliated with industry is not to be interpreted as government or industry endorsement of this code or standard.ASME accepts responsibilityfor 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.The American Society of Mechanical Engineers 345 East 47th Street,New York,NY 10017 Copyright 0 1998 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A.(This Foreword is not part of ASME B1.21M-1997.)This Metric Screw Thread Standard,MJ Profile,is a hard metric version similar to the UNJ Inch ASME BI.15 and MIL-S-8879 Standards which have a 0.1501 1P to 0.18042P controlled radius root in the external thread and the internal thread minor diameter truncated to accommodate the external thread maximum root radius.This metric thread is recommended for use in high temperature or high fatigue applications.Tolerance Class 4H5W4h6h is approximately equivalent to a Class 3M3B Inch J Thread and is intended for aerospace applications.Tabulated data has been provided for Tolerance Class 4g6g and 4G6G/4G5G for commercial applications or when the standard reduction for coating or plating provided in this Standard is not adequate for the coating thickness required.Table 6 in this issue has been added to define limiting dimensions for Tolerance Class 6g/6H for commercial producers and users of this class.Tolerance Class 6g/6H is intended for use only in commercial applications.This metric Standard has as its original basis the work done under the direction of the SAE E21E25 Metric Thread Panel,which developed and published SAE Aerospace Standard AS 1370.A replica of AS 1370 was ballot circulated in American National Standards Institute Committee B 1 as ANSI B1.21.Since the UNJ inch screw thread is predominantly used in aerospace designs,the aerospace industry decided to produce a hard metric version for aerospace metric design.The MJ screw thread project was initiated by SAE Committee E21,which was responsible for aerospace propulsion design standards.At the Committees October 25,1971 meeting,Project E21-122 was established to develop metric screw thread requirements for metric aerospace fasteners and threaded parts.A metric thread panel was organized to include representation from throughout the aerospace industry.Participating organizations included the following:SAEIE21-Aerospace Propulsion Design Standards SAEE25-Aerospace Propulsion Utility Parts Standards AIAAVASC-National Aerospace Standards Committee(airframe)ATA-Air Transport Association SBAC-Society of British Aircraft Constructors ALMA-American Locknut Manufacturers Association APFA-Aerospace Precision Fastener Association ASDNPAFB-Aeronautical Systems Division,U.S.Air Force NAPTC-Naval Air Propulsion Test Center,U.S.Navy Liaison representation from ANSYOMFS This Panel took into account the activities of ANSVOMFS,SBAC,ATA,AECMA,ISO/TC 20/SC 4,and ISO/TC I/SC 5 in order to reflect agreements compatible with international and U.S.aerospace metric screw thread requirements,as well as coordinating with ANSI/OMFS requ