1、 Intentionally left blank NATIONAL STANDARD GAGING FOR DRYSEAL PIPE THREADS (INCH) ASME B1.20.5-1991 (REVISION OF ANSI 81.20.5-1978) The American Society of Mechanical Engineers 345 East 47th Street, New York, N.Y. 1001 7 - Date of Issuance: March 15, 1991 This Standard will be revised when the Soci
2、ety 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 accredit
3、ed 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 oppor- tunity to participate. The proposed code or standard was made available for public
4、review and comment which provides an opportunity for additional public input from industry, academia, reg- ulatory 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
5、 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 expres
6、sly 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 endo
7、rsement 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 vol- unteers. No part of this document may be reproduced in any form, in an elect
8、ronic retrieval system or otherwise, without the prior written permission of the publisher. Copyright 0 1991 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A. (This Foreword is not part of ASME B1.20.5-1991.) In 1973, the American National Standards Committee B2,
9、which had formerly been re- sponsible for pipe thread standards, was absorbed by ANSI Standards Committee B1 and reorganized as subcommittee 20. A complete rewrite of the B2.2-1968 Standard on Dryseal Pipe Threads was completed with the publication of ANSI B1.20.3-1976 for product threads and the AN
10、SI B1.20.5-1978 Standard for Gaging. The product thread standard ANSI B1.20.3 establishes two classes of dryseal pipe threads: Class 1 and Class 2. The classes differ only in inspection requirements. With Class 1 threads, inspection of root and crest truncation is not specified. Class 2 threads are
11、identical to Class 1 threads except that inspection of root and crest truncation is required. This gaging standard includes 6-step crest and root check gages, which, within their limitations, should be helpful in establishing the degree of conformance of product threads. When 6-step crest or root ch
12、eck gages are to be used, it is necessary to classify the product thread size into a size range (minimum, basic, or maximum) as shown in Fig. 1. The use of 3-step L1 thread gages for NPTF threads requires estimating the one third of a turn, plus or minus, from the basic notch on the gage to classify
13、 the thread as basic. Use of this same one third turn estimation is required to determine minimum and maximum ranges. This Standard includes 4-step taper thread gages to eliminate the need for estimating the one third turn de- viation from basic necessary with 3-step or basic step gages. 3-step tape
14、r thread gages are included in Appendix A for those who may prefer to use them. Crest and root check gages for NPTF threads are also covered in this Standard. Prior to the - publication of ANSI B1.20.5-1978 many gage manufacturers had calculated diameters for and made such gages based on methods use
15、d for ANPT (MIL-P-7105) 6-step gages, which were calculated to the extremes of the minimum and maximum zones, where most product threads should never be, and which, further, is not the same logic used in calculating the pair of basic steps. The NPTF 6-step gages tabulated herein are based on the mid
16、-point of each range as determined by the L, plug gage (minimum, basic, or maximum) for calculation of the trun- cation limits where most of the product threads should be (see Fig. 2). It should be noted that all references to the turns of engagement method for inspection of product threads have bee
17、n withdrawn from this Standard. Results obtained by that method were found to quite often disagree with those obtained by the step limit method described here within. Also, inconsistencies in the end threads on the product and gages do not provide for a constant disengagement point between the two.
18、This does not however preclude the use of this method in any way as an acceptable means of inspecting taper pipe threads. When this method is chosen, customer and vendor should agree on gaging procedures and minimum/ maximum acceptance limits on the turns of engagement. Information on this method ca
19、n be found in Appendix D for reference. The gaging data in this Standard supersedes that given in ANSI B1.20.5-1978. The proposed standard was submitted by Standards Committee B1 to the Secretariat and the American Na- tional Standards Institute. It was approved and formally designated as an America
20、n National Standard on January 22, 199 1. 111 . Intentionally left blank ASME STANDARDS COMMITTEE B1 Standardization and Unification of Screw Threads (The following is the roster of the Committee at the time of approval of this Standard.) OFFICERS D. Emanuelli, Chairman H. W. Ellison, Vice Chairman
21、R. McGinnis, Secretary COMMITTEE PERSONNEL R. Anderson J. Bein A. Breed R. Browning R. Byrne D. Cadieux F. Cantrell R. Chamerda F. Ciccarone, Alternate R. Dodge P. Drake H. W. Ellison D. Emanuelli C. Erickson W. Farrell G. Flannery J. Heinz W. Jatho, Alternate F. Jones, Alternate S. Johnson S. Kante
22、r R. Lamport R. LaNier J. Levy K. McCullough J. McMurray A. Painter G. Russ R. Sabatos D. Satava M. Schuster E. Schwartz R. Searr R. Seppey A. Shepherd B. Shook A. Strang J. Sullivan R. Tennis A. Thibodeau J. Trilling M. Van Derwerken C. Wilson SUBCOMMITTEE B1.20 - PIPE THREADS D. P. Cadieux, Chairm
23、an A. F. Thibodeau. Secretary C. F. Banks M. J. Bibeau P. F. Braun J. A. Casner W. 0. Clinedinst F. Dallas Jr. D. M. Davidson R. Dodge W. C. Farrell Jr. L. S. Feldheim A. C. Flanders G. Flannery H. D. Goldberg S. I. Kanter W. A. Keaton M. W. Rose G. A. Russ A. D. Shepherd A. G. Strang V Intentionall
24、y left blank CONTENTS . Foreword . 111 Standards Committee Roster v 1 Gaging . 1 1.1 Scope 1 1.3 Limitations 1 . 1.2 How Dryseal Works . 1 1.4 Product Thread Designations 1 1.5 InspectionofProductThreads . 2 1.6 Methods of Gaging Product Threads 2 1.7 Coordination of Gages . 3 1.9 Direct Measurement
25、 of Crest and Root Truncation 5 1.10 Inspection of Gages . 5 1.8 UseofGages . 3 2 Gages 7 2.1 TypesandFunctionsofGages . 7 2.3 Thread Form . 8 2.2 Taper Thread Gages . 8 2.4 GageTolerance . 8 2.5 Working Gage Dimensions . 9 2.6 Master Gage Dimensions . 9 Figures 1 Classification of NPTF Product Thre
26、ad Size Using 4-Step Gages 4 2 Identification of Steps on 6-Step Crest or Root Check Gage 4 3 Relative Position Plus and Minus Standoff 6 4 Relative Position of Master Plugs and Rings to Working Gages . 10 Tables 1 GagesandTolerances . 2 2 Function and Application of Gages Covered in ASME B1.20.5-19
27、91 7 3 Tolerances for Working Plug and Ring Gages 11 4 Tolerances for Master Plug and Ring Gages . 12 5 Diameter Equivalent of Variation in Load for Tools and Gages . 13 6 Diameter Equivalent of Variation in Half Included Angle for Tools and Gages 14 7 Basic Dimensions for L1 Ring Gages . 16 8 Basic
28、 Dimensions for L, Short Ring Gages 18 9 Basic Dimensions for L2 Ring Gages . 20 10 Basic Dimensions for L, Short Ring Gages 22 11 Basic Dimensions for Crest Check Ring Gages 24 vii 12 13 14 15 16 17 18 19 20 21 22 23 Basic Dimensions for Root Check Ring Gages . Basic Dimensions for L1 Plug Gages. N
29、PTF Basic Dimensions for L1 Short Plug Gages Basic Dimensions for L, Plug Gages. NPSI . Basic Dimensions for L3 Plug Gages . Basic Dimensions for L, Short Plug Gages Basic Dimensions for Crest Check Plug Gages . Basic Dimensions for Root Check Plug Gages . Basic Dimensions of Master Ring Gages for L
30、. and L3 Taper Plug Gages . Basic Dimensions of Master Plug Gages for Z., and L, Taper Ring Gages . Basic Dimensions of Master Gages for 6-Step Crest Ring and 6-Step Crest PlugGages Basic Dimensions of Master Gages for 6-Step Root Ring Gages and 6-Step RootPlug Gages . 26 28 30 32 34 36 37 38 39 40
31、41 42 Appendices A 3-Step Gages for Checking NPTF Threads . 43 A1 WorkingGageDimensions 43 B Measurement of Pitch Diameter of Taper Threads Having an Included Taper of 0.0625 Inch per Inch 49 B1 Measurement of Pitch Diameter of Taper Thread Plug Gage . 49 B2 Measurement of Pitch Diameter of Taper Th
32、read Ring Gage . 53 C Formulas For Calculating 6-Step Taper Plug and Ring Gage Dimensions 57 D The Turns Engagement Method of Gaging Product Threads . 59 Figures B1 Measurement of Pitch Diameter of Taper Thread Gages by the 2-Wire Method 50 B2 Horizontal Measurement of Pitch Diameter of Taper Thread
33、 Gages by the 3-Wire Method Using Sine Block . 51 B3 Vertical Measurement of Pitch Diameter of Taper Thread Gages by the 3-Wire B4 Measurement of Pitch Diameter E, of Taper Thread Gages by the 4-Wire Method . 53 B5 Measurement of Pitch Diameter E, of Taper Thread Gages by the 4-Wire Method . 54 B6 M
34、easurement of Pitch Diameter of Taper Thread Ring Gage on Coordinate Method Using a Sine Fixture . 52 Measuring Machine With Ball Probe 55 Tables A1 Basic Di.mensions for L. 3-Step Ring Gages 44 A2 Basic Dimensions for L2 3-Step Ring Gages 45 A3 Basic Dimensions for L. 3-Step Plug Gages. NPTF 46 A4
35、Basic Dimensions for L3 3-Step Plug Gages 48 Dl Basic Turns Engagement 59 viii ASME B1.20.5-1991 GAGING FOR DRYSEAL PIPE THREADS (INCH) 1 GAGING 1 .I Scope The scope of this Standard is to provide information regarding practical dryseal thread inspection methods and commonly used gages for productio
36、n evaluation purposes. All dimensions are in inches unless otherwise specified. 1.1.1 Federal Government Use. When this Stan- dard is approved by the Department of Defense and the Federal agencies and is incorporated into FED-STD- H28/8, Screw-Thread Standards for Federal Services, Section 8, the us
37、e of this Standard by the Federal Gov- ernment is subject to all the requirements and limitations of FED-STD-H28/8. 1.2 How Dryseal Works The principle of dryseal threads is based on crest and root contact at handtight engagement at both major and minor diameters. Conformance to L, L2, and L3 func-
38、tional size gages alone will not assure that the threads will be drysealed to ANSI B1.20.3 design specfications. In addition to functional size, the dryseal crest and root truncations must be held on both external and internal threaded products in order to be dryseal. This applies to both straight a
39、nd taper dryseal threads. 1.3 Limitations Industry has developed gaging practices over many years which have resulted in the common use of L, L2, L, and plain taper plug and ring gages to evaluate dry- seal pipe threads. These are functional gages intended to aid the manufacturer in the control of t
40、hreading op- erations. It must be recognized that conformance to a functional gage or series of gages is not conclusive evi- dence of conformance to the design requirements of ANSI B1.20.3. For critical applications more extensive inspection and testing, not covered in this Standard, may be required
41、 in order to insure an acceptable seal. 1.3.1 These gaging practices used with proper tool configuration control, sound manufacturing and part support practices, and visual inspection have provided pipe threads that sealed acceptably for many producers of pipe threads. 1.3.2 These gages and gaging p
42、ractices are intended to evaluate unused pipe threads. Once a thread joint is made up wrench tight, metal is deformed by design and may not be found acceptable using these described gages and methods. It is the users responsibility to determine if the used thread will perform satisfactorily in its i
43、n- tended application. 1.4 Product Thread Designations Dryseal pipe threads are designated by specifying in sequence the nominal size, threads per inch, thread symbol, and class where required. EXAMPLES: 1/8-27 NPTF-1 1/8-27 NPTF-2 1/8-27 PTF-SAE SHORT 1/8-27 NPSF 1/8-27 NPSI Each of the letters in
44、the symbols has a definite signifi- cance as follows: N = National (American) Standard P = Pipe T = Taper S = Straight F = Fuel and Oil I = Intermediate For further information see ANSI B1.20.3. 1.4.1 Reference Documents. The latest issues of the following documents form a part of this Standard to t
45、he extent specified herein. ANWASME B1.7 Nomenclature, Definitions and Letter Symbols for Screw Threads ANSI B1.20.3 Dryseal Pipe Threads ANSI B47.1 Gage Blanks 1 ASME 81.20.5-1991 GAGING FOR DRYSEAL PIPE THREADS (INCH) TABLE I .GAGES AND TOLERANCES Product Thread Thread to be Note (111 Tolerance No
46、te (1 11 Gaged With Gaged Limit Method of Gaging Tolerance Applied to Basic Size NPTF, external Plus (small) Minus (large) L, or L, short and Note (2)l 1 turn 1 turn PTF-SAE L2 or L2 short ring gages Plus (small) Minus (large) SHORT, external 1.5 turn 0 turn Threads are within the NPTF, internal Plu
47、s (large) Minus (small) allowable tolerance when the product reference point is on or L, or L, short and Note (3)l L, or L3 short plug gages PTF-SAE between the maximum SHORT, internal and minimum step of 1.5 turn 0 turn the L, gage Plus (large) Minus (small) NPSF, internal 1.5 turn 0 turn L, or L,
48、short plug gage Plus (large) Minus (small) NPSI, internal 0.5 turn 1 turn NOTES: (1) Step limit gages with 4 (or 3) steps should be used. (2) The difference in engagement of the L, versus Lz ring gages shall not exceed 0.5 turn. See para. 1.8.4. (3) The difference in engagement of the L, versus L, p
49、lug gages shall not exceed 0.5 turn. See para. 1.8.4. 1.5 Inspection of Product Threads 1.5.1 Inspection of NPTF Class 1 Threads and PTF-SAE Short Threads. Acceptability is determined by coordinated use of L, and L2 gages for external prod- uct threads and L, and L3 gages for internal product threads. Crest and root truncation is generally consid- ered to be controlled by tooling or other means. 1.5.2 Inspection of NPTF Class 2 Threads. Ac- ceptability is determined, in part, by coordinated use of L, and L
