2006_2021.pdf

AN AMERICAN NATIO NAL STANDARDScrew Threads:Nomenclature,Definitions,and Letter Symbols ASME B1.7-2006(Revision of ANSI/ASME B1.7M-1984)REAFFIRMED 2021Intentionally left blank ASME B1.7-2006(Revision of ANSI/ASME B1.7M-1984)Screw Threads:Nomenclature,Definitions,andLetter SymbolsThree Park Avenue New York,NY 10016AN AMERICAN NATIONAL STANDARDDate of Issuance:November 17,2006This Standard will be revised when the Society approves the issuance of a new edition.There will beno 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 the procedures accredited as meeting the criteria for American NationalStandards.The Standards Committee that approved the code or standard was balanced to assure that individuals fromcompetent and concerned interests have had an opportunity to participate.The proposed code or standard was madeavailable for public review and comment,which provides an opportunity for additional public input from industry,aca-demia,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 itemsmentioned in this document,and does not undertake to insure anyone utilizing a standard against liability for infringe-ment of any applicable letters patent,nor assumes any such liability.Users of a code or standard are expressly advisedthat determination of the validity of any such patent rights,and the risk of infringement of such rights,is entirely theirown responsibility.Participation by federal agency representative(s)or person(s)affiliated with industry is not to be interpreted as gov-ernment or industry endorsement of this code or standard.ASME accepts responsibility for only those interpretations of this document issued in accordance with the establishedASME procedures and policies,which precludes the issuance of interpretations by individuals.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 EngineersThree Park Avenue,New York,NY 10016-5990Copyright 2006 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.CONTENTSForeword.vCommittee Roster .vi1General .12Definition of Terms .1Figures1Allowance.22Axis of Thread .23Best Wire Size.24Blunt Start Thread .35Bottom of Chamfer.46Clearance Flank .47Countersink .48Crest.49Root and Crest Truncation.510Fundamental Deviation .611Metric Tolerance System for Screw Threads .712Element.713Flank.714Flank Angle .715Flat Form .716Following Flank .817Gauge Plane .818Height of Fundamental Triangle .819Height of Thread .920Height of Thread Engagement.921Helix.922Helix Variation(Drunken Thread).923Incomplete Thread .1024Interference Fit .1125Internal Thread.1126Lead .1127Leading Flank.1128Gaging Length .1129Length of Assembly .1130Length of Thread Engagement.1231Load Flank .1232Major Clearance .1233Major Diameter,External Thread.1234Major Diameter,Internal Thread .1235Major Diameter,Internal Thread(Rounded Form).1236Major Diameter,Taper Thread.1237Minor Clearance.1338Minor Diameter,External Thread(Flat Form).1439Minor Diameter,External Thread(Rounded Form).1440Minor Diameter,Internal Thread.1441Minor Diameter,Taper Thread .1442Multiple Start Thread.14iii43Pitch .1444Pitch Cone .1445Pitch Cylinder .1446Pitch Diameter,External Thread .1547Pitch Diameter,Internal Thread.1548Plane of Vanish Point.1549Profile,Basic Thread.1650Root Radius .1651Screw Thread .1652Sharp Crest and Root.1653Shear Area .1754Straight Thread.1855Thread Angle .2356Thread Ridge Thickness.2357Truncation .2358Vanish Cone.24Tables1General Symbols.192ISO General Symbols .203Thread Series Designations .214ISO Thread Series Designations .22Nonmandatory AppendicesASuperseded Thread Series Designations.25BISO Symbols for Screw Threads.26CGreek Alphabet .27ivFOREWORDThe first revision of ASA B1.7-1949,the first American Standard on Nomenclature,Definitions,and Letter Symbols for Screw Threads,was approved in January 1965.These earlier definitionsand symbols were subsequently published as appendix material in ASA B1.1,B2.1,and B2.2.Assuch they underwent some revision over the years.A draft based on such revisions,dated July1961,was prepared by Subcommittee 8 and widely circulated by the sponsors for comment.Ex-tensive comments were received from members of Sectional Committee B1,B2,B4,and others,which were reviewed and acted upon at a meeting of Subcommittee 8,held November 28,1961.A second revised draft,dated July 1962,was prepared and submitted to the American-British-Canadian Conference on Engineering Standards,held in Harriman,New York on September2226,1962.Suggested revisions agreed upon by the co