1、BS 7371-12:2008Coatings on metal fasteners Part 12: Requirements for imperial fastenersICS 25.220.40; 21.060.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPublishing and copyright informationThe BSI copyright notice displayed in this document indicates when
2、the document was last issued. BSI 2008ISBN 978 0 580 60930 5The following BSI references relate to the work on this standard:Committee reference FME/9/1Draft for comment 08/30173610 DCPublication historyFirst published July 2008Amendments issued since publicationAmd. no. Date Text affectedBS 7371-12
3、:2008 BSI 2008 iBS 7371-12:2008ContentsForeword ii1 Scope 12 Normative references 13 Terms and definitions 14 Screw thread dimensions 15 Coating thickness 26 Application and type of coating 27 Measurement of coating thickness 2AnnexesAnnex A (informative) Strip and weigh method for the determination
4、 of group and sample average plating thickness of silver 8Bibliography 9List of tablesTable 1 Plating thickness 2Table 2 Screws and bolts: B.S.W. and B.S.F. threads 3Table 3 Screws and bolts: UNC and UNF threads 4Table 4 Screws and bolts: B.A. threads 5Table 5 Screws and bolts: B.S.C. and B.S.P. thr
5、eads 5Table 6 Nuts: B.S.W. and B.S.F. threads 6Table 7 Nuts: B.A. threads 6Table 8 Nuts: UNC and UNF threads 7Summary of pagesThis document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 9 and a back cover.BS 7371-12:2008ii BSI 2008ForewordPublishing informationThis Briti
6、sh Standard is published by BSI and came into effect on 31 July 2008. It was prepared by Technical Committee FME/9/1, Coatings on threaded components and accessories. A list of organizations represented on this committee can be obtained on request to its secretary.Information about this documentThis
7、 standard supersedes all parts of BS 3382, which are withdrawn.Presentational conventionsThe provisions of this standard are presented in roman (i.e. upright) type.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”.Commentary, explanation and general inform
8、ative 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 application.Compliance with a British Sta
9、ndard cannot confer immunity from legal obligations. BSI 2008 1BS 7371-12:20081 ScopeThis standard gives thickness requirements for coatings on imperial metal fasteners and can be used in conjunction with all parts of BS 7371.NOTE 1 For information on coating materials, see the relevant part of BS 7
10、371.This standard does not cover components such as self-tapping screws and wood screws.This standard includes area tables (in square inch units) for imperial fasteners, and factors for thickness determination (see Table 2 to Table 8).NOTE 2 Details concerning cadmium have not been included in this
11、standard due to the restrictions placed on the marketing and use of cadmium and its compounds contained in national and international regulations.2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition c
12、ited 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: Specification for gauges for screw threads of unified formBS 7371-1, Coatings on metal fasteners Specification for general r
13、equirements and selection guidelinesBS 7371-3, Coatings on metal fasteners Part 3: Specification for electroplated zinc coatingsBS 7371-4, Coatings on metal fasteners Part 4: Specification for electroplated nickel, nickel/chromium and copper/nickel/chromium coatings3 Terms and definitionsFor the pur
14、poses of this British Standard, the terms and definitions given in BS 7371-1 apply.4 Screw thread dimensionsThread dimensions of components supplied for plating and after plating shall conform to the relevant screw thread standards. NOTE See BS 919-1:2007, Annex D for the gauging procedure to be use
15、d.After plating, thread dimensions of components shall be in accordance with the appropriate clauses of BS 919-1:2007, Annex D.BS 7371-12:20082 BSI 20085 Coating thicknessThe thickness to be applied to imperial fasteners made to standard dimensions shall be in accordance with Table 1, however, if th
16、e maximum batch average thickness exceeds that specified in Table 1, the parts can be accepted if they conform when tested with the appropriate GO gauge.6 Application and type of coatingZinc electroplating shall be applied in accordance with BS 7371-3.Nickel or nickel plus chromium on steel or coppe
17、r alloy (including brass) components shall be applied in accordance with BS 7371-4. NOTE 1 Thicker coatings are also dealt with in the above parts.NOTE 2 For tin on steel, copper and copper alloy components, see BS 1872.NOTE 3 For silver on steel, copper and copper alloy components, see BS 2816.7 Me
18、asurement of coating thicknessCoating thickness shall be calculated in accordance with BS 7371-3 for zinc coatings, and BS 7371-4 for nickel and copper coatings. NOTE 1 See Table 2 to Table 8 for surface areas of imperial fasteners with areas in square inches.NOTE 2 The value of K for areas in squar
19、e inches (K) is as follows: for zinc, K = 219, assuming a density of 7.1 g/cm3; for nickel and copper, K = 174, assuming a density of 8.8 g/cm3; for tin (see BS 1872:1984, B.2.5) K = 212, assuming a density of 7.3 g/cm3.These values will give thickness in microns. For silver, see BS 2816, but for av
20、erage thickness use the strip and weigh method (see Annex A). To convert inch dimensions to microns, multiply by 2.54 103.Table 1 Plating thicknessBasic major diameter of screw threadinBatch average thicknessOver Up to and including Minimum Maximum0.060 0.126 3.8 5.10.126 0.250 5.1 6.40.250 0.500 6.
21、4 7.60.500 0.750 7.6 8.9NOTE It is recommended that components with threads of basic major diameters greater than in be plated to the requirements of BS EN 12329.34- BSI 20083BS 7371-12:2008Table 2 Screws and bolts: B.S.W. and B.S.F. threadsArea per inch length of shanksquare inchesArea of headsquar
22、e inchesNominalsizeinThreaded shank Unthreaded shankCountersunk headRaised countersunk headRound headPanheadCheese headRaised cheese headMushroom headHexagon headNominal diameter Rolling diameterB.S.W or B.S F.B.S.W. B.S.F. B.S W. or B.S.F.B.S.W. B.S.F. BS 450 BS 450 BS 450 BS 450 BS 450 BS 450 BS 4
23、50 BS 450 (below in) and BS 10830.579 0.390 0.339 0.099 0.108 0.118 0.151 0.117 0.144 0.166 0.1380.725 0.487 0.425 0.155 0.169 0.184 0.238 0.183 0.237 0.1830.857 0.894 0.584 0.502 0.523 0.224 0.242 0.265 0.351 0.265 0.339 0.390 0.301 1.046 0.682 0.612 0.306 0.331 0.362 0.451 0.362 0.452 0.4721.164 1
24、.205 0.782 0.682 0.705 0.402 0.436 0.474 0.605 0.473 0.599 0.646 0.6251.480 1.516 0.977 0.867 0.887 0.629 0.698 0.741 0.949 0.742 0.924 0.960 0.8631.792 1.835 1.175 1.049 1.074 0.905 0.989 1.067 1.348 1.067 1.343 1.332 1.1662.096 2.151 1.370 1.228 1.259 1.235 1.455 1.851 1.456 1.431 1.6592.391 2.463
25、 1.565 1.400 1.442 1.614 1.901 2.414 1.905 1.922 2.2112.726 2.798 1.762 1.596 1.638 2.043 2.406 2.703 2.414 2.8283.035 3.103 1.957 1.778 1.817 2.522 2.970 3.239 2.982 3.4333.675 3.732 2.350 2.152 2.185 3.634 4.276 4.113 4.295 4.92214-18-532-316-732-14-516-38-716-12-916-58-34-4BSI 2008BS 7371-12:2008
26、Table 3 Screws and bolts: UNC and UNF threadsArea per inch length of shanksquare inchesArea of headsquare inchesNominal sizeThreadedshankUnthreaded shankCountersunk (flat) headRaised countersunk (oval) headPan headRaised cheese (fillister)headHexagon headNominal diameterRolling diameterUNC or UNFUNC
27、 UNFUNC or UNFUNC UNF BS 1981 BS 1981 BS 1981 BS 1981 BS 17680 0.275 0.187 0.163 0.025 0.028 0.035 0.031 1 0.333 0.339 0.227 0.198 0.201 0.038 0.044 0.052 0.046 2 0.395 0.403 0.268 0.234 0.238 0.054 0.059 0.070 0.063 0.0473 0.454 0.464 0.309 0.269 0.275 0.073 0.081 0.093 0.084 0.0934 0.508 0.523 0.3
28、49 0.298 0.309 0.096 0.104 0.121 0.108 0.0975 0.578 0.586 0.390 0.342 0.346 0.119 0.129 0.152 0.136 0.1036 0.626 0.647 0.430 0.367 0.383 0.147 0.160 0.184 0.166 0.1848 0.764 0.777 0.512 0.448 0.459 0.209 0.227 0.261 0.236 0.19910 0.867 0.903 0.594 0.509 0.530 0.281 0.305 0.349 0.318 0.29312 1.006 1.
29、027 0.675 0.593 0.606 0.368 0.386 0.450 0.414 0.330in1.158 1.209 0.782 0.680 0.709 0.489 0.531 0.605 0.558 0.5631.473 1.522 0.977 0.865 0.893 0.772 0.841 0.952 0.875 0.7831.783 1.856 1.175 1.047 1.090 1.113 1.215 1.355 1.265 0.9992.086 2.161 1.370 1.226 1.269 1.236 1.855 1.333 1.2842.401 2.495 1.565
30、 1.411 1.466 1.409 2.423 1.816 1.7782.712 2.810 1.762 1.594 1.651 1.851 2.182 2.1523.020 3.144 1.957 1.775 1.847 2.383 3.252 2.583 2.7803.657 3.789 2.350 2.149 2.226 3.629 4.132 3.428 4.00514-516-38-716-12-916-58-34- BSI 2008 5BS 7371-12:2008Table 4 Screws and bolts: B.A. threads Area per inch lengt
31、h of shanksquare inchesArea of headsquare inchesNominal size B.A.Threaded shankUnthreaded shank Cheese headRound headCountersunk headRaised countersunk headHexagon headNominal diameterRolling diameterBS 57 BS 57 BS 57 BS 57 BS 570 1.114 0.738 0.665 0.534 0.423 0.339 0.367 0.5391 0.981 0.650 0.586 0.
32、418 0.332 0.268 0.288 0.4202 0.868 0.578 0.518 0.318 0.253 0.205 0.220 0.3313 0.754 0.503 0.450 0.248 0.197 0.163 0.181 0.2514 0.659 0.443 0.393 0.197 0.157 0.131 0.139 0.1935 0.585 0.393 0.349 0.150 0.120 0.101 0.110 0.1526 0.509 0.342 0.303 0.116 0.093 0.078 0.085 0.1177 0.453 0.305 0.270 0.092 0.
33、073 0.063 0.070 0.0938 0.397 0.267 0.237 0.075 0.060 0.051 0.056 0.0729 0.340 0.232 0.203 0.050 0.040 0.034 0.037 0.05310 0.303 0.207 0.181 0.038 0.031 0.026 0.029 0.042Table 5 Screws and bolts: B.S.C. and B.S.P. threadsDimensions in inches Area per inch length of shankNominal size B.S.C. threads to
34、 BS 811 B.S.C. fastening threads to BS EN ISO 228Threaded shank Unthreaded shank Threaded shank Unthreaded shankNominal diameterRolling diameterNominal diameterRolling diameter0.537 0.390 0.348 1.929 1.197 1.1280.672 0.487 0.436 0.824 0.584 0.534 0.957 0.682 0.620 1.108 0.782 0.718 2.596 1.621 1.518
35、1.260 0.880 0.816 1.411 0.977 0.914 1.714 1.175 1.111 3.337 2.055 1.9522.017 1.370 1.307 2.320 1.565 1.503 2.623 1.762 1.700 2.926 1.957 1.896 3.229 2.152 2.092 3.533 2.350 2.289 18-532-316-732-14-932-516-38-716-12-916-58-1116-34-BS 7371-12:20086 BSI 2008Table 6 Nuts: B.S.W. and B.S.F. threadsArea o
36、f nutsquare inchesNominal sizeB.S.W or B.S F. inOrdinary Thin Slotted CastleBS 450 (below in) and BS 1083BS 450 (below in) and BS 1083BS 1083 BS 10830.17 0.14 0.21 0.18 0.36 0.31 0.56 0.47 0.64 0.53 0.80 0.810.92 0.76 1.05 1.121.26 1.03 1.34 1.491.78 1.45 1.91 2.192.38 1.94 2.56 2.893.03 2.46 3.25 3
37、.763.69 3.00 3.95 4.515.29 4.29 5.65 6.48Table 7 Nuts: B.A. threadsArea of nut square inchesNominal size, B.A. Ordinary ThinBS 57 BS 570 0.59 0.511 0.46 0.402 0.36 0.313 0.28 0.244 0.22 0.185 0.17 0.146 0.13 0.1170.18 0.08 0.0790610 0.05 14-14-18-532-316-732-14-516-38-716-12-916-58-34- BSI 2008 7BS
38、7371-12:2008Table 8 Nuts: UNC and UNF threadsArea of nut square inchesNominal size UNC or UNFOrdinary (precision)Thin Slotted Thick slotted Hexagon machine screw nut (pressed)Square machine screw nut (pressed)BS 1768 BS 1768 BS 1768 BS 1768 BS 1981 BS 1981 0 0.07 0.081 0.07 0.082 0.10 0.123 0.10 0.1
39、24 0.19 0.225 0.29 0.346 0.29 0.348 0.36 0.4210 0.41 0.4812 0.58 0.66in 0.66 0.56 0.72 0.81 0.62 0.720.89 0.74 0.95 1.05 0.99 1.141.18 0.95 1.24 1.39 1.23 1.421.71 1.40 1.82 2.01 2.10 1.76 2.21 2.55 2.78 2.33 2.96 3.35 3.27 2.69 3.45 4.04 4.72 3.81 4.97 5.59 14-516-38-716-12-916-58-34-BS 7371-12:200
40、88 BSI 2008Annex A (informative) Strip and weigh method for the determination of group and sample average plating thickness of silverA.1 Thoroughly clean and free each group of items from grease.A.2 Thoroughly dry each group of items.A.3 Weigh each group of items together or in such small groups as
41、are appropriate to the maximum capacity of the balance to an accuracy of 1 mg on each weighing.A.4 Totally immerse each group of items in the following stripping solution, and turn each item over in the solution to permit free access of the liquid to all surfaces:a) sulphuric acid (d 1.84): 19 parts
42、 by volume;b) nitric acid (d 1.42): 1 part by volume;c) temperature: 60 C70 C.A.5 Remove items from the stripping solution immediately the coating is completely dissolved, then totally immerse in sulphuric acid (d 1.84) for a few seconds. This operation minimizes attack on the base metal during the
43、early stages of the final rinsing.A.6 Remove items from the sulphuric acid, wash well with cold running water, wipe and immerse in clean acetone to remove any trapped water. Dry each item, and reweigh each group exactly as before.A.7 Deduce the weight of plating for each group by subtraction of the
44、results of the weighings, or evaluate it from the stripping solutions by a normal method of chemical estimation (e.g. potentiometric titration with a standard sodium chloride solution).A.8 Calculate the areas of coatings of the ten or more items in the group from the data given in Table 2 to Table 8
45、.A.9 Calculate the group average thickness (assuming a relative density of 10.5 for the silver deposit, i.e. 172 g/in3) from:Group average thickness = weight of coating (g)area of coating in2()172-inweight of coating (g)area of coating (cm2) 10.5- cm.= BSI 2008 9BS 7371-12:2008BibliographyFor dated
46、references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.BS 57, Specification B.A. screws bolts and nutsBS 450, Specification for machine screws and machine screw nuts (B.S.W. & B.S.F. threads)BS 811, Specifi
47、cation for cycle (B.S.C.) threads (formerly known as C.E.I. threads)BS 1083, Specification for precision hexagon bolts, screws and nuts (B.S.W. & B.S.F. threads)BS 1768, Specification for unified precision hexagon bolts, screws, & nuts (UNC & UNF threads) Normal seriesBS 1872:1984, Specification for electroplated coatings of tinBS 1981, Specification for unified machine screws and machine screw nutsBS 2816, Method for specifying electroplated coatings of silver and silver alloys for engineering purpos
