ASME_B1-15-1995.pdf

Copyrighted material licensed to Stanford University by Thomson Scientific(),downloaded on Oct-05-2010 by Stanford University User.No further reproduction or distribution is permitted.Uncontrolled when printed.AN ASME STANDARD Unified Inch Screw Threads(UNJ Thread Form)ASME B1.15-1995 The American Society of Mechanical Engineers 345 East 47th Street,New York,N.Y.-Copyrighted material licensed to Stanford University by Thomson Scientific(),downloaded on Oct-05-2010 by Stanford University User.No further reproduction or distribution is permitted.Uncontrolled when printed.Date of Issuance:August 15,1995 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 agen-cies,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(s)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 volun-teers.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 1995 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in USA.Copyrighted material licensed to Stanford University by Thomson Scientific(),downloaded on Oct-05-2010 by Stanford University User.No further reproduction or distribution is permitted.Uncontrolled when printed.FOREWORD(This Foreword is not part of ASME B1.15-1995.)This Standard is similar to Military Specification MIL-S-8879 and equivalent to ISO-3161-1977 for thread Classes 3A and 3B.British Standard BS 4084:1978 including Amend-ment 1 is technically identical to ISO-3161-1977 except for Appendix A which provides information for a 20 UNJ constant pitch series for diameters through 3 inches.The UNJ thread form,having the enlarged root radius in the external thread,was introduced for applications requiring high fatigue strength where working stress levels are high,in order to minimize size and weight in parts,as in aerospace applications and also for other designs in commercial products where stresses are critical.To meet these requirements,the UNJ external thread root radius is designed between 0.1501 lPto 0.18042P and the minor diameter of the mating internal thread is increased to ensure the necessary clearance.This Standard includes Classes 2A and 2B UNJ screw threads.Either Class 3 or Class 2 UNJ threads are appropriate for commercial applications commensurate with the fatigue and stress levels required.It is not recommended that Classes 2A and 2B threads be used for aerospace applications.Only UNJ thread Classes 3A and 3B meet the requirements of Military Specification MIL-S-8879.NOTE:In what follows,the symbols H and h are used.H is defined as the height of the sharp vee thread formed by extending the thread flanks until they meet.H is equal to 0.866025 times the pitch,P.The symbol h is equal to 0.75 times H and represents the theoretical height of the American National thread form.It is still used as the basis for the value called percent of thread.The UNJ thread form is the UN thread form modified to 9/16 H or 75%h basic thread depth which allows the 0.18042P maximum root radius in the external thread.The first known U.S.standard of similar thread form was the Society of Automotive Engineers Aeronautical Standard AS 82 published in March 1942,which is a modified American National thread form to 75%h basic thread depth and specifying 0.108P-0.18OP root radius in the external thread.This thread was symbolized NR,National Round,and was developed fo