1、BS 1580-3:2007Unified screw threads Part 3: Screw threads with diameters below in RequirementsICS 21.040.2014-NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document indicates when t
2、he document was last issued. BSI 2007ISBN 978 0 580 57927 1The following BSI references relate to the work on this standard:Committee reference FME/9Draft for comment 07/30158492 DCPublication historyFirst published August 1965Second edition, December 2007Amendments issued since publicationAmd. no.
3、Date Text affectedBS 1580-3:2007 BSI 2007 iBS 1580-3:2007ContentsForeword iii1 Scope 12 Normative references 13 Terms and definitions and symbols 14 Thread profiles 15 Diameter/pitch combinations 26 Tolerance classes 27 Tolerances, allowances and limits of size for uncoated threads 28 Coated threads
4、 39 Designation of threads 410 Gauges 4AnnexesAnnex A (normative) Unified screw threads below in diameter for attachment purposes and for general use in the aircraft industry 16Bibliography 17List of tablesTable 1 Unified screw threads below in diameter, standard series 5Table 2 Unified screw thread
5、s below in diameter, standard series Limits of size 6Table 3 Coarse thread series (UNC) below in diameter Limits and tolerances for finished uncoated threads External threads Class 2A 8Table 4 Coarse thread series (UNC) below in diameter Limits and tolerances for finished uncoated threads Internal t
6、hreads Class 2B 8Table 5 Coarse thread series (UNC) below in diameter Limits and tolerances for finished uncoated threads External threads Class 3A 9Table 6 Coarse thread series (UNC) below in diameter Limits and tolerances for finished uncoated threads Internal threads Class 3B 9Table 7 Fine thread
7、 series (UNF) below in diameter Limits and tolerances for finished uncoated threads External threads Class 2A 10Table 8 Fine thread series (UNF) below in diameter Limits and tolerances for finished uncoated threads Internal threads Class 2B 10Table 9 Fine thread series (UNF) below in diameter Limits
8、 and tolerances for finished uncoated threads External threads Class 3A 11Table 10 Fine thread series (UNF) below in diameter Limits and tolerances for finished uncoated threads Internal threads Class 3B 11Table 11 Extra fine thread series (UNEF) below in diameter Limits and tolerances for finished
9、uncoated threads External threads Classes 2A and 3A 12Table 12 Extra fine thread series (UNEF) below in diameter Limits and tolerances for finished uncoated threads Internal threads Classes 2B and 3B 12Table 13 Coarse thread series (UNC) sizes below in diameter Basic dimensions 1314-14-14-14-14-14-1
10、4-14-14-14-14-14-14-14-BS 1580-3:2007ii BSI 2007Table 14 Fine thread series (UNF) sizes below in diameter Basic dimensions 13Table 15 Extra fine thread series (UNEF) sizes below in diameter Basic dimensions 14Table 16 Thread data for unified thread form 24 t.p.i. to 80 t.p.i. 1514-14- BSI 2007 iiiBS
11、 1580-3:2007ForewordPublishing informationThis part of BS 1580 is published by BSI and came into effect on 31 December 2007. It was prepared by Subcommittee SFTSE/1, Screws and fasteners technical specification committee, under the authority of Technical Committee FME/9, Nuts, bolts and accessories.
12、 A list of organizations represented on this committee can be obtained on request to its secretary.SupersessionThis part of BS 1580 supersedes BS 1580-3:1965, which is withdrawn.Relationship with other publicationsBS 1580 is now published in two parts Part 1: Screw threads with diameters in and larg
13、er Requirements Part 3: Screw threads with diameters below in Requirements This part of BS 1580 is intended for use with BS 919-1 which specifies the corresponding screw gauges.Information about this documentThis part of BS 1580 has been fully revised to bring it up to date.The range of diameters co
14、vered by this part of BS 1580 falls within the range of the B.A. screw thread sizes given in BS 93. The various pitches given for the same diameter in the unified system, however, offer a wider selection of diameter/pitch combinations for specific applications than do those in the B.A. system. The U
15、NF series gives the closest approximation to the B.A. diameter/pitch combinations.Hazard warningsPresentational conventionsThe provisions of this standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.Commenta
16、ry, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct applica
17、tion.Compliance with a British Standard cannot confer immunity from legal obligations.WARNING. Attention is drawn to the fact that, with the different screw thread forms available, there is the possibility of a mismatch, which is potentially hazardous. It is the responsibility of the designer of the
18、 end product to ensure that this possibility is reduced to a minimum. For further information on mismatches of screw thread systems see PD 6494.14-14-iv BSI 2007 This page deliberately left blankBS 1580-3:2007 BSI 2007 1BS 1580-3:20071 ScopeThis part of BS 1580 specifies limits of sizes, and toleran
19、ces, for single-start, clearance-fit unified screw threads, in inch units with diameters below in.This part of BS 1580 specifies unified screw threads from Number 0 (0.060 in diameter) to Number 12 (0.216 in diameter), known as the “numbered sizes” in the following standard series: a coarse thread (
20、UNC) series; a fine thread (UNF) series; for Number 12 threads, an extra fine (UNEF) 32 threads per inch diameter/pitch combination.NOTE Unified screw threads below in diameter for attachment purposes and for general use in the aircraft industry are specified in Annex A.2 Normative referencesThe fol
21、lowing referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.BS 919-1:2007, Screw gauge limits and tolerances Part 1:
22、Specification for gauges for screw threads of unified formBS 1580-1:2007, Unified screw threads Part 1: Screw threads with diameters in and larger Requirements BS 1981, Specification for unified machine screws and machine screw nutsBS 6528:1984, Glossary of terms for cylindrical screw threads3 Terms
23、 and definitions and symbols3.1 Terms and definitionsFor the purposes of this part of BS 1580 the terms and definitions given in BS 6528:1984 and in BS 1580-1:2007 apply.3.2 SymbolsFor the purposes of this part of BS 1580 the symbols given in BS 1580-1:2007 apply.4 Thread profilesThe basic profile a
24、nd the design profile shall be as specified in BS 1580-1:2007, Clause 4.The dimensions of the thread profile shall be as specified in Table 16.14-14-14-BS 1580-3:20072 BSI 20075 Diameter/pitch combinationsThe diameter/pitch combinations for standard series unified threads below in diameter shall be
25、as specified in Table 1.NOTE Where possible, the use of No. 1, No. 3 and No. 12 sizes should be avoided and preference should be given to the first choice sizes listed in Column 1.6 Tolerance classesExternal threads and internal threads shall be of one of the following tolerance classes as specified
26、 in BS 1580-1:2007, Clause 6:a) external threads:Clas 2A;Clas 2AG (se Note 1)Clas 3A;b) internal threads:Clas 2B;Clas 3B.NOTE 1 These are Class 2A coated threads where the allowance has to be maintained after coating.NOTE 2 Classes 1A and 1B specified in BS 1580-1 are not considered suitable for the
27、 sizes of unified screw threads specified in this part of BS 1580.NOTE 3 Owing to the tendency for close-fitting external and internal threads made of stainless steel to seize when tightened together, it is recommended that stainless steel external and internal uncoated threads should not be made to
28、 Class 3 limits but rather to Class 2 limits.7 Tolerances, allowances and limits of size for uncoated threadsTolerances, allowances and limits of size for finished uncoated threads shall be as given in Table 2.NOTE 1 The limits and tolerances for threads specified in Table 2 are repeated in Table 3
29、to Table 12, separated according to series and tolerance class for the convenience of users of this standard.NOTE 2 The tolerances and allowances for unified screw threads below inch diameter, of Classes 2A, 2B, 3A and 3B have been based on the same formulae as those for the larger diameters (see BS
30、 1580-1:2007, Annex A) with the exception of the tolerances for the minor diameters of Class 2B internal threads which are the same as those for Class 3B internal threads. These tolerances have been calculated from the following formula: with a maximum tolerance of 0.394P.NOTE 3 The effective diamet
31、er tolerances have been based on a length of engagement between and 1 times the nominal major diameter. For adjustment of these tolerances for shorter lengths of engagement see BS 1580-1:2007, Clause 7 Note 4. NOTE 4 The values given for the minimum major diameters of internal threads are not realiz
32、ed in practice as the roots of the threads are always cleared above the minimum major diameter.14-14-3 20.05 0.03 / 0.002PPD+23-12- BSI 2007 3BS 1580-3:20078 Coated threads8.1 GeneralNOTE 1 Electroplated coatings on threaded components (cadmium on steel components and zinc on steel components) are s
33、pecified in BS 3382: Parts 1No. 1: No increase;No. 2: 0.000 3 in; No. 3: 0.000 4 in; No. 4: 0.000 5 in;No. 5: 0.000 6 in; No. 6: 0.000 7 in; No. 8: 0.000 8 in;No. 10: 0.001 in; No. 12, 0.001 in.BS 1580-3:20074 BSI 2007The maximum limits before coating shall remain unchanged. NOTE 2 The tolerances re
34、sulting from the amounts recommended in Note 1 are substantially the same as those for Class 3B, and are considered to be a practical minimum. It is, therefore, strongly recommended that coated Class 2B threads be used instead of coated Class 3B threads.8.6 Class 3B internal threadsClass 3B coated t
35、hreads shall be not smaller than the minimum limits given in Table 2 and shall be accepted by a GO screw gauge of basic size. NOTE If before coating these minimum limits are increased by the amounts recommended for Class 2B threads (see 8.5 Note 1) and the maximum limits remain unchanged, the result
36、ing working tolerances might be too small to be practical. To remedy this, it might then be necessary to increase the maximum limits by the same amounts as those recommended for the minimum limits. The resulting maximum limits would then be substantially the same as the Class 2B maximum limits. For
37、this reason that it is strongly recommended that coated Class 2B threads (see 8.5) be used instead of coated Class 3B threads.9 Designation of threads9.1 Basic designationThe numbered sizes of unified screw threads shall have a basic designation comprising the following:a) the thread number;NOTE Thi
38、s may be followed by the nominal size in parentheses.b) the number of threads per inch;c) the thread series, UNC, UNF or UNEF;d) the thread class, 2A, 2AG, 3A, 2B or 3B.EXAMPLES6 (0.138) 32 UNC 2A12 (0.216) 28 UNF 3B12 (0.216) 32 UNEF 2A9.2 Additional designationsFor coated threads and threads with
39、other special characteristics, the basic designation shall be followed by the relevant additional designation(s) given in BS 1580-1:2007, Clause 11.10 GaugesGauges conforming to BS 919-1 shall be used.NOTE It is recommended that the American-type high-addendum NOT GO effective diameter screw plug ga
40、uge be used for checking the numbered sizes of internal threads. BSI 2007 5BS 1580-3:2007Table 1 Unified screw threads below in diameter, standard series(Extension of Table 1 of BS 1580-1)Designation numbers Basic major diameter Threads per inch Designation numbersSeries with graded pitches1st choic
41、e 2nd choice Coarse UNC Fine UNF Extra fine UNEFin0 0.060 0 80 01 0.073 0 64 72 12 0.086 0 56 64 23 0.099 0 48 56 34 0.112 0 40 48 45 0.125 0 40 44 56 0.138 0 32 40 68 0.164 0 32 36 8 10 0.190 0 24 32 1012 0.216 0 24 28 32 12NOTE 1 The diameter/pitch combinations of the UNF series are substantially
42、similar to those of B.A. threads as specified in BS 93, but the coarse series threads might be more suitable for use with certain materials.NOTE 2 For the values of the basic dimensions of the UNC, UNF and UNEF threads, see Table 13, Table 14 and Table 15, respectively.14-6BSI 2007BS 1580-3:2007Tabl
43、e 2 Unified screw threads below in diameter, standard series Limits of size(Extension of Table 2 of BS 1580-1)1 2 34 5 6 7 8 9 101112131415161718Nominal size and threads per inchSeries designationExternal threads Internal threads Class Allowance Major diameter Effective diameter Minor diameter Class
44、 Minor diameter Effective diameter Major diameterMax. Min. Max. Min. Tol. Max. Min. Min. Max. Min. Max. Tol. Min.in in in in in in in in in in in in in in0-80 UNF 2A 0.000 5 0.059 5 0.056 3 0.051 4 0.049 6 0.001 8 0.044 2 0.041 5 2B 0.046 5 0.051 4 0.051 9 0.054 2 0.002 3 0.060 0 3A 0.000 0 0.060 0
45、0.056 8 0.051 9 0.050 6 0.001 3 0.044 7 0.042 5 3B 0.046 5 0.051 4 0.051 9 0.053 6 0.001 7 0.060 01-64 UNC 2A 0.000 6 0.072 4 0.068 6 0.062 3 0.060 3 0.002 0 0.053 2 0.050 1 2B 0.056 1 0.062 3 0.062 9 0.065 5 0.002 6 0.073 0 3A 0.000 0 0.073 0 0.069 2 0.062 9 0.061 4 0.001 5 0.053 8 0.051 2 3B 0.056
46、 1 0.062 3 0.062 9 0.064 8 0.001 9 0.073 01-72 UNF 2A 0.000 6 0.072 4 0.068 9 0.063 4 0.061 5 0.001 9 0.055 4 0.052 5 2B 0.058 0 0.063 5 0.064 0 0.066 5 0.002 5 0.073 0 3A 0.000 0 0.073 0 0.069 5 0.064 0 0.062 6 0.001 4 0.056 0 0.053 6 3B 0.058 0 0.063 5 0.064 0 0.065 9 0.001 9 0.073 02-56 UNC 2A 0.
47、000 6 0.085 4 0.081 3 0.073 8 0.071 7 0.002 1 0.063 5 0.060 1 2B 0.066 7 0.073 7 0.074 4 0.077 2 0.002 8 0.086 0 3A 0.000 0 0.086 0 0.081 9 0.074 4 0.072 8 0.001 6 0.064 1 0.061 2 3B 0.066 7 0.073 7 0.074 4 0.076 5 0.002 1 0.086 02-64 UNF 2A 0.000 6 0.085 4 0.081 6 0.075 3 0.073 3 0.002 0 0.066 2 0.
48、063 0 2B 0.069 1 0.075 3 0.075 9 0.078 6 0.002 7 0.086 0 3A 0.000 0 0.086 0 0.082 2 0.075 9 0.074 4 0.001 5 0.066 8 0.064 1 3B 0.069 1 0.075 3 0.075 9 0.077 9 0.002 0 0.086 03-48 UNC 2A 0.000 7 0.098 3 0.093 8 0.084 8 0.082 5 0.002 3 0.072 7 0.068 9 2B 0.076 4 0.084 5 0.085 5 0.088 5 0.003 0 0.099 0
49、 3A 0.000 0 0.099 0 0.094 5 0.085 5 0.083 8 0.001 7 0.073 4 0.070 2 3B 0.076 4 0.084 5 0.085 5 0.087 7 0.002 2 0.099 03-56 UNF 2A 0.000 7 0.098 3 0.094 2 0.086 7 0.084 5 0.002 2 0.076 4 0.072 9 2B 0.079 7 0.086 5 0.087 4 0.090 2 0.002 8 0.099 0 3A 0.000 0 0.099 0 0.094 9 0.087 4 0.085 8 0.001 6 0.077 1 0.074 2 3B 0.079 7 0.086 5 0.087 4 0.089 5 0.002 1 0.09
