Pipe Threads, 60 deg, General PurposeA N A M E R I C A N N A T I O N A L S T A N D A R DPipe Threads, 60deg, General Purpose 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 DThree Park Avenue • New York, NY 10016Date of Issuance:June15,2007This 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. Periodically,certain actions of the ASME B1Committee may be published as Cases.Cases are published on the ASME Web site under the Committee Pages at as they are issued.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 Standards 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 that 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 ers 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 of this document issued in accordance with the established ASME 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,NY10016-5990Copyright©2007byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.CONTENTSForeword (iv)Committee Roster (v)Correspondence With the B1Committee (vi)1Scope (1)2Reference and Symbols (1)3Taper Pipe Thread Form (1)4Specifications for General Purpose Taper Pipe Threads,NPT (8)5Specifications for Internal Parallel Threads in Pipe Couplings,NPSC (8)6Gauges and Gauge Tolerances for Standard Pipe Thread,NPT (8)7Gauging of Taper Pipe Thread,NPT (11)8Gauging of NPSC Parallel Pipe Threads (11)Figures1Standard Taper Pipe Thread Notation (2)2Basic Profile of Standard Taper Pipe Thread (3)3Standard Taper Pipe Threads for Pressure-Tight Joints (5)4NPT Standard Taper Pipe Thread Plug and Ring Gauges (12)5Suggested Form of Gauge Thread (12)6Gauging External Taper Threads With Ring Gauge (12)7Gauging Internal Taper Threads With Plug Gauge (12)8Gauging of Chamfered Threads (18)Tables1Limits on Crest and Root Truncation of Standard External and InternalTaper Pipe Threads (4)2Basic Thread Dimensions (6)3Tolerances on Taper,Lead,and Angle of Pipe Threads,NPT (9)4Dimensions,Internal Parallel Threads in Pipe Couplings,NPSC (9)5Basic Dimensions of Plug and Ring Gauges for NPT Threads (13)6Tolerances for NPT Working Plug and Ring Gauges (14)7Diameter Equivalent of Variation in Lead for Tools and Gauges (16)8Diameter Equivalent of Variation in Half Included Angle of Thread forTools and Gauges (17)Nonmandatory AppendicesA The Turns of Engagement Method of Verifying Product Threads (19)B Tap Drill Sizes (20)iiiFOREWORDThis Standard is a metric conversion of the data for NPT inch series taper pipe threads and NPSC inch series straight internal pipe threads.The NPT and NPSC inch threads are included in ANSI/ASME B1.20.1,Pipe Threads,General Purpose(Inch).Threads and gages delineated herein are interchangeable with those in ANSI/ASME B1.20.1.Tabulated metric values have been converted from values in ANSI/ASME B1.20.1and rounded in accordance with ASME B1.30, Screw Threads:Standard Practice for Calculating and Rounding Dimensions.Values are given in millimeters.When compared to values calculated from formulas in this Standard,there may be a difference in the last decimal place but this will not affect interchangeability.The ASME B1Subcommittee20 prepared this metric Standard in order to encourage global use of the NPT Pipe Thread.For ease of use,both product threads and gauging are contained in this one Standard.Nonmandatory Appendices A and B are informative only and are not considered a part of this Standard. ASME B1.20.2M was approved by the American National Standards Institute on December 21,2006.ivASME B1COMMITTEEStandardization and Unification of Screw Threads(The following is the roster of the Committee at the time of approval of this Standard.)STANDARDS COMMITTEE OFFICERSA.L.Barrows,Chair D.S.George,Vice Chair A.L.Guzman,SecretarySTANDARDS COMMITTEE PERSONNELA.L.Barrows,Kennametal–IPGF.G.Calderone,Corresponding Member,Quality Systems ImplementersR.Dodge,Pennoyer-Dodge Co.D.Everett,National Institute of Standards and Technology G.A.Flannery,Corresponding Member,Mercury Gage Co.H.N.Frost,Defense Supply Center Philadelphia J.O.Gehret III,Vermont Thread Gage D.S.George,Ford Motor Co.J.R.Gervasi,Kerr Lakeside,Inc.J.Greenslade,Greenslade and Co.L.C.Borowski,Alternate,Greenslade and Co.A.L.Guzman,The American Society of Mechanical Engineers R.J.Hukari,SPS TechnologiesL.C.Johnson,The Johnson Gage Co.D.D.Katz,Precision Fittings R.P .Knittel,Leitech-US Ltd.P rouche,Swanson Tool Manufacturing Co.SUBCOMMITTEE 20—PIPE THREADSD.D.Katz,Chair,Precision Fittings K.Bly,Hemco GagesM.Hop,Alternate,Hemco GagesF.G.Calderone,Corresponding Member,Quality Systems ImplementerJ.A.Casner,Corresponding Member,Casner Engineering Services M.Cox,Corresponding Member,Frank J.Cox Sales,Ltd.R.Dodge,Pennoyer-Dodge Co.G.A.Flannery,Corresponding Member,Mercury Gage Co.D.D.Gajdosik,Besly Products Corp.J.O.Gehret III,Vermont Thread Gage J.R.Gervasi,Kerr Lakeside,Inc.J.A.Gruber,Wheatland Tube Co.L.C.Johnson,The Johnson Gage Co.vrzelere,Corresponding Member,Deltronic Corp.L.L.Lord,Corresponding Member,Caterpillar,Inc.M.H.McWilliams,PMC Lonestar D.Miskinis,Kennametal–IPGW.R.Newman,Corresponding Member,Consultant D.R.Oas,Seaway Bolt and Specials Corp.M.W.Rose,Glastonbury Southern GageW.A.Watts,Alternate,Glastonbury Southern Gage E.Schwartz,ConsultantR.H.Searr,Member Emeritus,Mak Tool and Gage B.F.Sheffler,Dresser-Rand Co.A.D.Shepherd,Jr.,Emuge Corp.D.Skierski,Sterling Gage and Calibration LLC R.D.Strong,General Motors Corp.A.F.Thibodeau,Member Emeritus,Swanson Tool Manufacturing Co.R.E.Vincent,Jr.,General Plug Manufacturing Co.C.J.Wilson,Industrial Fasteners InstituteR.P .Knittel,Leitech–US Ltd.P rouche,Swanson Tool Manufacturing rzelere,Corresponding Member,Deltronic Corp.M.H.McWilliams,PMC Lone StarD.R.Maisch,Alternate,PMC Lone Star D.R.Oas,Seaway Bolt and Specials Corp.J.R.Popovic,Cleveland Specialty Inspection Services M.W.Rose,Glastonbury Southern GageR.H.Searr,Corresponding Member,Consultant A.D.Shepherd,Jr.,Emuge Corp.D.Skierski,Sterling Gage and Calibration LLCA.F.Thibodeau,Corresponding Member,Swanson Tool Manufacturing Co.R.E.Vincent,Jr.,General Plug Manufacturing Co.CORRESPONDENCE WITH THE B1COMMITTEE General.ASME Standards are developed and maintained with the intent to represent the consensus of concerned interests.As such,users of this Standard may interact with the Committee by requesting interpretations,proposing revisions,and attending Committee meetings.Corre-spondence should be addressed to:Secretary,B1Standards CommitteeThe American Society of Mechanical EngineersThree Park AvenueNew York,NY10016-5990Proposing Revisions.Revisions are made periodically to the Standard to incorporate changes that appear necessary or desirable,as demonstrated by the experience gained from the application of the Standard.Approved revisions will be published periodically.The Committee welcomes proposals for revisions to this Standard.Such proposals should be as specific as possible,citing the paragraph number(s),the proposed wording,and a detailed description of the reasons for the proposal,including any pertinent documentation. Proposing a Case.Cases may be issued for the purpose of providing alternative rules when justified,to permit early implementation of an approved revision when the need is urgent,or to provide rules not covered by existing provisions.Cases are effective immediately upon ASME approval and shall be posted on the ASME Committee Web page.Requests for Cases shall provide a Statement of Need and Background Information.The request should identify the standard,the paragraph,figure or table number(s),and be written as a Question and Reply in the same format as existing Cases.Requests for Cases should also indicate the applicable edition(s)of the standard to which the proposed Case applies.Attending Committee Meetings.The B1Standards Committee regularly holds meetings,which are open to the public.Persons wishing to attend any meeting should contact the Secretary of the B1Standards Committee.viASME B1.20.2M-2006PIPE THREADS,60deg,GENERAL PURPOSE1SCOPEThis Standard specifies the designations,dimensions, and tolerances and establishes a verification system for 60deg included angle pipe threads.It is applicable for general purpose pipe and fitting connections.Where pressure-tight joints are required,it is intended that taper pipe threads conforming to this Standard be made up wrench-tight with a sealant.To prevent galling on certain piping materials such as stainless steel,the seal-ant should contain a lubricant.Internal parallel(straight)pipe threads,series NPSC, are used with external taper pipe threads,series NPT. Internal taper pipe threads,series NPT,are used with external taper pipe threads,series NPT.2REFERENCE AND SYMBOLS2.1Reference StandardThe following publication is referenced in this Stan-dard.The latest edition shall apply.ASME B1.20.1,Pipe Threads,General Purpose(Inch) Publisher:The American Society of Mechanical Engineers(ASME),Three Park Avenue,New York, NY10016-5900;Order Department:22Law Drive, P.O.Box2300,Fairfield,NJ07007-23002.2SymbolsThe following symbols are used(see Fig.1):D p outside diameter of pipeE0p basic pitch diameter at small end of external thread(or end of pipe)E1p basic pitch diameter at plane of hand-tight engagement length(L1),external thread,largeend of internal threadE2p basic pitch diameter at plane of effective thread length(L2),external threadE3p basic pitch diameter at plane of wrench-tight engagementE5p basic pitch diameter at L5K0p basic minor diameter at small end of external thread(or end of pipe)L1p length of hand-tight engagement between internal and external threadsL2p length of effective thread,external threadL3p length of thread beyond L1allowing wrench-tight engagement,internal thread;alsowrench makeup1L4p overall length of thread,including vanish thread,external threadL5p length of complete threads,external thread V p vanish thread(s),allowance for chamfer on tool-ing or other process of thread production3TAPER PIPE THREAD FORM3.1Thread ProfileThe form of thread profile specified in this Standard shall be known as the Standard Taper Pipe Thread Form. The relations as specified herein for form of thread and general notation are shown in Fig.2.3.2Angle of ThreadThe angle between the sides of the thread is60deg when measured in an axial plane.The line bisecting this angle is perpendicular to the axis.3.3Truncation and Thread HeightThe height,H,of the sharp V thread isH p0,866025PwhereP p pitch of threadThe basic maximum height of the truncated thread,h, (see Fig.2)is based on factors entering into the manufac-ture of cutting tools and the making of tight joints.Maximum h p0,800000PThe crest and root of pipe threads are truncated a minimum of0,033000P.The maximum depth of trunca-tion for the crest and root of these pipe threads will be found in Table1.The crest and roots of external and internal threads may be truncated either parallel to the pitch line or parallel to the axis.The illustration in Fig.2,giving a sectional view of this standard thread form,represents the truncated thread form by a straight line.However,when closely examined,the crests and roots of commercially manufac-tured pipe threads appear slightly rounded.When crests and roots of threading tools or chasers lie within the limits shown in Table1,the pipe threads of products produced by such means are acceptable on the basis of in-process control.NotationFig.1Standard Taper Pipe ThreadD 305122ASME B1.20.2M-2006Fig.2Basic Profile of Standard Taper PipeThreadInternal ThreadExternal ThreadwhereF c p width of flat at crest F r p width of flat at rootf c p depth of truncation at crest f r p depth of truncation at rootH p 0,866025P p height of 60deg sharp V thread h p 0,800000P p height of thread on product n p number of threads per 25,4mmP p 25,4/n p pitch (measured parallel to axis)␣p 30deg p thread flank angle p 1°47′p thread taper per sideGENERAL NOTE:For a symmetrical parallel screw thread,H p 25,4(cot ␣)/2n .For a symmetrical taper screw thread,the exact value for Standard taper pipe thread is H p 0,865743P .For a 3,175mm pitch thread,which is the coarsest standard taper pipe thread pitch,the corresponding values of H are 2,74873and 2,74963,the difference being 0,00090mm.This difference being too small to be significant,the value of H p 0,866025P continues in use for threads of 1⁄16taper on the diameter.3ASME B1.20.2M-2006T a b l e 1L i m i t s o n C r e s t a n d R o o t T r u n c a t i o n o f S t a n d a r d E x t e r n a l a n d I n t e r n a l T a p e r P i p e T h r e a d sI n t e r n a l T h r e a dE x t e r n a l T h r e a dH e i g h t o f H e i g h t N u m b e r S h a r p V T r u n c a t i o n ,fE q u i v a l e n t W i d t h o fF l a t ,Fo f T h r e a d ,o f T h r e a d s ,T h r e a d ,h ,m m M i n i m u mM a x i m u mT o l e r a n c eM i n i m u mM a x i m u mT o l e r a n c en ,H ,p e r 25,4m mm mM a x .M i n .F o r m u l am m F o r m u l a m mm mF o r m u l am mF o r m u l am mm m1234567891011121314270,814830,7530,6340,033P 0,0300,096P 0,0910,0610,038P 0,0360,111P 0,1040,068181,221991,1290,9740,033P 0,0460,088P 0,1240,0790,038P 0,0530,102P 0,1450,092141,571241,4511,2880,033P 0,0610,078P 0,1420,0810,038P 0,0690,090P 0,1630,09411,51,912871,7671,5900,033P 0,0740,073P 0,1600,0860,038P 0,0840,084P 0,1850,10182,749552,5402,3560,033P 0,1040,062P0,1980,0940,038P0,1220,072P0,2290,107G E N E R A L N O T E :T h e b a s i c d i m e n s i o n s o f t h e S t a n d a r d T a p e r P i p e T h r e a d a r e g i v e n i n m i l l i m e t e r s t o t h r e e ,f o u r ,a n d f i v e d e c i m a l p l a c e s .W h i l e t h i s i m p l i e s a g r e a t e r d e g r e e o f p r e c i s i o n t h a n i s o r d i n a r i l y a t t a i n e d ,t h e s e d i m e n s i o n s a r e s o e x p r e s s e d f o r t h e p u r p o s e o f e l i m i n a t i n g e r r o r s i n c o m p u t a t i o n s .4ASME B1.20.2M-2006Fig.3Standard Taper Pipe Threads for Pressure-TightJointsInternal ThreadExternal Thread5ASME B1.20.2M-2006T a b l e 2B a s i c T h r e a d D i m e n s i o ns6ASME B1.20.2M-2006T a b l e 2B a s i c T h r e a d D i m e n s i o n s (C o n t ’d )N o m .P i t c h C o m p l e t e B a s i c N u m b e r D i a m .,O v e r a l l H a n d -t i g h t E f f e c t i v e T h r e a d ,E x t e r n a l M i n o r W r e n c h M a k e u p L e n g t h N o m .o f a t L e n g t h E n g a g e m e n t E x t e r n a l T h r e a d s L e n g t h ,L 1D i a m .C h a n g e i n f o r I n t e r n a l T h r e a dO .D .T h r e a d s ,B e g i n -o f [N o t e (5)]L e n g t h ,L e n g t h ,P l a n e t o L 2a t S m a l l D i a m ./o f n ,P i t c h n i n g o fP i t c h P i t c h E x t e r n a l H e i g h t L 1L 2P l a n e ,E x t e r n a l L e n g t h V a r n i s h L e n g t h ,D i a m .,E n d o f T h r e a d N o m .P i p e ,p e r o f E x t e r n a l D i a m .P i t c h D i a m .,T h r e a d ,o f [N o t e (1)][N o t e (3)]T h r e a d (L 2−L 1)L 3T h r e a d ,V L 5E 5P i p e ,K 0(0,0625/n )P i p e D ,25,4T h r e a d ,T h r e a d ,[N o t e (2)]D i a m .,E 3,L 4,m m T h r e a d ,S i z e m m m m P E 0m mT h r e a d s E 1m m T h r e a d s E 2m mT h r e a d s m m T h r e a d s m m m m T h r e a d s [N o t e (4)]m m m m h m m m m1234567891011121314151617181920212223241⁄167,9270,9416,8884,0644,327,1426,6327,057,3032,5682,732,82236,7123,2643,479,8964,7507,1850,7536,1370,0591⁄810,3270,9419,2334,1024,369,4896,7037,129,6522,6012,762,82239,0573,2643,479,9674,8219,5340,7538,4810,0591⁄413,7181,41112,1265,7864,1012,48710,2067,2312,7644,4203,134,234311,8614,8973,4715,1037,38412,5871,12910,9960,0883⁄817,1181,41115,5456,0964,3215,92610,3587,3416,1934,2623,024,234315,2814,8973,4715,2557,53616,0161,12914,4170,0881⁄221,3141,81419,2648,1284,4819,77213,5567,4720,1115,4282,995,443318,9246,2943,4719,8509,92919,8851,45117,8130,1133⁄426,7141,81424,5798,6114,7525,11713,8617,6425,4455,2502,895,443324,2396,2943,4720,15510,23425,2191,45123,1270,113133,411,52,20930,82610,1604,6031,46117,3437,8531,9107,1833,256,627330,4127,6633,4725,00612,92631,6341,76729,0600,13811⁄442,211,52,20939,55110,6684,8340,21817,9538,1340,6737,2853,306,627339,1377,6633,4725,61613,53640,3971,76737,7850,13811⁄248,311,52,20945,62110,6684,8346,28718,3778,3246,7697,7093,496,627345,2067,6633,4726,04013,96046,4931,76743,8530,138260,311,52,20957,63311,0745,0158,32519,2158,7058,8348,1413,696,627357,2197,6633,4726,87814,79858,5581,76755,8670,13821⁄273,083,17569,07617,3235,4670,15928,8939,1070,88211,5703,646,350268,67911,0163,4739,90922,54370,4852,54066,5350,198388,983,17584,85219,4566,1386,06830,4809,6086,75711,0243,476,350284,45511,0163,4741,49624,13086,3602,54082,3110,19831⁄2101,683,17597,47320,8536,5798,77631,75010,0099,45710,8973,436,350297,07611,0163,4742,76625,40099,0602,54094,9330,1984114,383,175110,09321,4386,75111,43333,02010,40112,15711,5823,656,3502109,69611,0163,4744,03626,670111,7602,540107,5540,1985141,383,175136,92523,8007,50138,41235,72011,25139,15711,9203,756,3502136,52811,0163,4746,73629,370138,7602,540134,3840,1986168,383,175163,73124,3337,66165,25238,41812,10166,13214,0844,446,3502163,33411,0163,4749,43432,068165,7352,540161,1910,1988219,183,175214,21327,0008,50215,90143,49813,70216,93216,4975,206,3502213,81611,0163,4754,51437,148216,5352,540211,6730,19810273,183,175267,85130,7349,68269,77248,89515,40270,90718,1615,726,3502267,45411,0163,4759,91142,545270,5102,540265,3110,19812323,983,175318,33334,54410,88320,49253,97517,00321,70719,4316,126,3502317,93711,0163,4764,99147,625321,3102,540315,7930,19814355,683,175349,88539,67512,50352,36557,15018,00353,45717,4755,506,3502349,48811,0163,4768,16650,800353,0602,540347,3450,1981640683,175400,36846,02514,50403,24462,23019,60404,25716,2055,106,3502399,97111,0163,4773,24655,880403,8602,540397,8280,1981845783,175450,85050,80016,00454,02567,31021,20455,05716,5105,206,3502450,45311,0163,4778,32660,960454,6602,540448,3100,1982050883,175501,33353,97517,00504,70672,39022,80505,85718,4155,806,3502500,93611,0163,4783,40666,040505,4602,540498,7930,1982461083,175602,29860,32519,00606,06882,55026,00607,45722,2257,006,3502601,90111,0163,4793,56676,200607,0602,540599,7580,198G E N E R A L N O T E :T h e b a s i c d i m e n s i o n s o f t h e N P T S t a n d a r d T a p e r P i p e T h r e a d a r e g i v e n i n m i l l i m e t e r s t o t h r e e ,f o u r ,a n d f i v e d e c i m a l p l a c e s .W h i l e t h i s i m p l i e s a g r e a t e r d e g r e e o f p r e c i s i o n t h a n i s o r d i n a r i l y a t t a i n e d ,t h e s e d i m e n s i o n s a r e t h e b a s i s o f g a u g e d i m e n s i o n s a n d a r e s o e x p r e s s e d f o r t h e p u r p o s e o f e l i m i n a t i n g e r r o r s i n c o m p u t a t i o n s .N O T E S :(1)A l s o l e n g t h o f t h i n r i n g g a u g e a n d l e n g t h f r o m g a u g i n g n o t c h t o s m a l l e n d o f p l u g g a u g e .(2)A l s o p i t c h d i a m e t e r a t g a u g i n g n o t c h (h a n d -t i g h t p l a n e ).(3)A l s o l e n g t h o f p l u g g a u g e .(4)T h e l e n g t h ,L 5,f r o m t h e e n d o f t h e p i p e d e t e r m i n e s t h e p l a n e b e y o n d w h i c h t h e t h r e a d f o r m i s i n c o m p l e t e a t t h e c r e s t .A t t h i s p l a n e t h e c o n e f o r m e d b y t h e c r e s t o f t h e t h r e a d i n t e r -s e c t s t h e c y l i n d e r f o r m i n g t h e e x t e r n a l s u r f a c e o f t h e p i p e .T h e n e x t t w o t h r e a d s a r e c o m p l e t e a t t h e r o o t L 5p L 2−2P (5)R e f e r e n c e d i m e n s i o n .7ASME B1.20.2M-20064SPECIFICATIONS FOR GENERAL PURPOSE TAPER PIPE THREADS,NPT4.1Taper Pipe Threads,NPTNPT threads made in accordance with these specifica-tions consist of an external taper and an internal taper thread,to form the normal type of joint having general application on pipe and fittings.See Fig.3.NPT taper pipe threads are intended to be made up wrench-tight and with a sealant whenever a pressure-tight joint is required.Sealing is affected by out-of-roundness,which is pos-sible between the wrench-tight mated parts in final assembly.This will vary depending on the method for producing the thread in conjunction with the elasticity and/or ductility of the mating parts and the resultant conformance at final assembly.4.1.1Thread Designation.NPT taper pipe thread designation shall consist of the following sequence: nominal pipe size;dash;number of threads per25,4mm; and“NPT.”If the thread is left-handed,add“-LH.”Right-handed threads require no special designation. EXAMPLE:1⁄4-18NPT1⁄4-18NPT-LHNOTE:Each letter in the symbol,NPT,has a definite significance as follows:N p National(American)standard,P p Pipe,T p Taper.4.1.2Thread Dimensions.Basic dimensions are specified in Table2.See para.3.1for profile.4.1.3Taper of Thread.The taper of the thread is1in16measured on the diameter and along the axis.4.1.4Engagement Between External and Internal Taper Threads.The normal length of engagement between external and internal taper threads when screwed together hand-tight is shown in Columns6and7of Table2.This length is controlled by the construction and use of the gauges.It is recognized that in special applications,such as flanges for high-pressure work, longer thread engagement is used,in which case the pitch diameter(dimension E1in Table2)is maintained and the pitch diameter,E0,at the end of the pipe is proportionately smaller.4.2Tolerances4.2.1Manufacturing Tolerances on Product.The maximum allowable variation in the product is one turn, large or small,from gauges made to the basic dimen-sions.See paras.7.1and7.2for gauging.4.2.2Tolerances on Thread Elements.The permissi-ble variations in thread elements are given in Table3. This table is a guide for establishing limits of the thread elements of taps,dies,and thread chasers.Conformance8to these limits may be required on product threads,in which case specifications shall require control and check-ing of thread elements.On pipe fittings and valves(not steel or high-grade alloys used in critical services)for steam pressures 2,1MPa and below,it is intended that plug and ring gauge practices as established in this Standard be used in conjunction with tooling control of thread elements, e.g.,taps and dies,to provide satisfactory control of functional size.Therefore,no tolerances on thread ele-ments have been established for this class.For service conditions,where more exact checks are required,procedures have been developed by industry to supplement the standard plug and ring gauge method of gauging.5SPECIFICATIONS FOR INTERNAL PARALLEL THREADS IN PIPE COUPLINGS,NPSC5.1Parallel Pipe Threads in Pipe Couplings Threads in pipe couplings made in accordance with these specifications are parallel threads of the same thread form as the Standard Taper Pipe Thread specified in para.3.1.They are used to form pressure-tight joints when assembled with a NPT external taper pipe thread, and made up wrench-tight with lubricant or sealant.5.1.1Thread Designation.Standard parallel pipe thread designation shall consist of the following sequence:nominal pipe size;dash;number of threads per25,4mm;and“NPSC.”If the thread is left-handed, add“-LH.”Right-handed threads require no special des-ignation.EXAMPLE:1⁄4-18NPSC1⁄4-18NPSC-LHNOTE:Each letter in the symbol,NPSC,has a definite signifi-cance as follows:N p National(American)standard,P p Pipe, S p Straight(parallel),C p Coupling.5.1.2Thread Dimensions.The thread dimensions are specified in Table4.The pitch diameter limits of size correspond to one and one-half turns,large or small,of the Standard Taper Pipe Thread.The major and minor diameters vary with the pitch diameter,as the Standard Pipe Thread Form is maintained within the truncated tolerances shown in Table1.6GAUGES AND GAUGE TOLERANCES FOR STANDARD PIPE THREAD,NPT6.1Design of GaugesGauges for Standard Pipe Threads in this Standard provide a functional check and are of the standard type as described below.ASME B1.20.2M-2006Table3Tolerances on Taper,Lead,and Angle of Pipe Threads,NPTTolerance,Tolerance,Lead in60degTolerance,TaperNumber of Length of Angle ofon Pitch LineThreads,Effective Threads,(1⁄16or3°34′on Diameter)Nominal n,per Threads,deg, Pipe Size25,4mm Max.Min.±±1234561⁄16,1⁄827+0,36′−0,18′0,07621⁄21⁄4,3⁄818+0,36′−0,18′0,07621⁄2,3⁄414+0,36′−0,18′0,076121,11⁄4,11⁄2,211,5+0,36′−0,18′0,076111⁄221⁄2and larger8+0,36′−0,18′0,076111⁄2 GENERAL NOTE:For tolerances on height of thread,see Table1;for tolerances on functional size,see para.4.2.1.NOTE:(1)The tolerance on lead shall be±0,003mm/mm on any size threaded to an effective thread lengthgreater than25,4mm.Table4Dimensions,Internal Parallel Threads in Pipe Couplings,NPSCNumber ofPitch Diameter Nominal Nominal Threads,n,Minor[Note(1)]Pipe O.D.of per Diameter,Size Pipe,D25,4mm Minimum Min.Max.1234561⁄810,3278,6369,4019,5781⁄413,71811,22712,35512,6193⁄817,11814,65615,79416,0581⁄221,31418,16119,60119,9423⁄426,71423,49524,94825,288 133,411,529,48931,25531,669 11⁄442,211,538,25240,01040,424 11⁄248,311,544,32346,08146,495 260,311,556,36358,11858,532 21⁄273,0867,31069,86070,457 388,9883,23685,77186,365 31⁄2101,6895,93698,47899,073 4114,38108,585111,135111,730 NOTE:(1)Attention is called to the fact that the actual pitch diameter of the parallel thread will be slightlysmaller than the value given when gauged with a taper plug gauge as specified in para.9.1.9。
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