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1、BRITISH STANDARD BS 3382: Parts 5 Part 2: Zinc on steel components; Part 3: Nickel or nickel plus chromium on steel components; Part 4: Nickel or nickel plus chromium on copper and copper alloy (including brass) components; Part 5: Tin on copper and copper alloy (including brass) components; Part 6:
2、 Silver on copper and copper alloy (including brass) components; Part 7: Thicker platings for threaded components (which deals with those special cases where greater protection than that provided by Parts 1 to 6 inclusive is required). Parts 5 and 6 deal with thicknesses of plating which, without se
3、riously interfering with the assembly of threaded componenets, will ensure the best protection against corrosion which is possible on threads conforming to tolerances and allowances laid down in relevant screw thread standards. These will be adequate for most purposes on copper and copper alloys. Gr
4、eater thicknesses cannot be accommodated on standard threads without undue risk of interference. Guidance is given in Parts 5 and 6 as to the degree of protection which will be afforded by the coating. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy,
5、 (c) BSI BS 3382: Parts 5 BS 811 and BS 2779 provide no such allowances. NOTE 2It is recommended that components with threads of basic major diameters greater than in be plated to the requirements of BS 1872, “Electroplated coatings of tin”, or BS 2816, “Electroplated coatings of silver”. NOTE 3Surf
6、ace areas of these components may be calculated from Table 2 to Table 10. Surface areas of other components should be agreed between the manufacturer and the purchaser. 2 Definitions For the purposes of this British Standard the following definitions apply: production batch a quantity of identical c
7、omponents, plated together at one time in a particular barrel delivery batch a consignment of identical components received by the purchaser under cover of one delivery note, and comprising some or all of the constituents of any number of production batches batch average thickness (applicable to pro
8、duction and delivery batches) the average thickness of the coating on all the components of a batch. The average thickness of a delivery batch is dependent upon the average thicknesses and the sizes of all relevant production batches group ten or more items selected at random from a production batch
9、 or from each fifty-six pounds or any remainder of a delivery batch batch sample a representative number of components of a batch composed either of one group or of any number of groups 1) The threads referred to in these standards are now considered obsolescent and their use is not recommended. 2)
10、BS 57, “B.A. screws, bolts and nuts”. BS 450, “Machine screws and machine screw nuts (B.S.W. and B.S.F. threads)”. BS 1083, “Precision hexagon bolts, screws and nuts (B.S.W. and B.S.F. threads)”. BS 1768, “Unified precision hexagon bolts, screws and nuts (UNC and UNF threads) Normal series”. BS 1981
11、, “Unified machine screws and machine screw nuts”. BS 3155, “American machine screws and nuts in sizes below ! in diameter”. BS 3692, “Dimensions of ISO metric precision bolts, screws and nuts”. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy, (c) BS
12、I BS 3382: Parts 5 methods to minimize this deterioration in appearance and also a method for preventing spotting out of the plating solution from pores in the basis metal are given in Appendix M. 13 Finish and appearance of plated surfaces 13.1 Components plated with silver or silver plus anti-tarn
13、ish treatment shall be free from visible defects such as unplated or “burnt” areas, blisters and nodules. 13.2 Components which have received anti-tarnish treatment should be virtually the same in appearance as those which have not received the treatment, but may exhibit a very light bluish irridesc
14、ence. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3382: Parts 5 & 6:1967 6 BSI 09-1999 Table 1 Plating thickness (Inch dimensions) Table 1A Plating thickness (Millimetre dimensions) Basic major diameter of screw threadBatch average th
15、ickness OverUp to and includingMinimumMaximum inininin 0.0600.1260.000 150.000 20 0.1260.2500.000 200.000 25 0.2500.5000.000 250.000 30 0.5000.7500.000 300.000 35 Basic major diameter of screw threadBatch average thickness OverUp to and includingMinimumMaximum mmmmmmmm 1.523.200.003 80.005 1 3.206.3
16、50.005 10.006 4 6.3512.700.006 40.007 6 12.7019.050.007 60.008 9 NOTE 1It is recommended that components with threads of basic major diameters greater than # in be plated to the requirements of BS 1872, “Electroplated coatings of tin”, or BS 2816, “Electroplated coatings of silver”. NOTE 2Thickness
17、values in Table 1 and Table 1A are inclusive of any nickel or copper undercoating. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3382: Parts 5 & 6:1967 BSI 09-19997 Appendix D Notes on surface areas of screws, bolts and nuts5) D.1 Gener
18、al Tables of surface areas of standard screws, bolts and nuts are given in Table 2 Table 10 as a guide to electroplaters so that they may estimate the conditions of current and plating time necessary to obtain the required deposit thickness and also to assist in the estimation of average thickness o
19、n plated components. The tables enable the electroplater to find the surface area of screws and bolts by a simple calculation from values obtained from the tables, and the surface area of nuts directly from the tables. The tables cover a range of screws, bolts and nuts having a basic major thread di
20、ameter of from 0.06 to 0.75 in. D.2 Screws and bolts Table 2 Table 6 give values for the calculation of surface areas of general purpose screws and bolts. To obtain the total surface area of a screw or bolt the following values which are given in the tables are necessary: 5) It has been considered a
21、ppropriate to retain in Parts 5 and 6 the same appendix and figure references, for the same contents, as the existing Parts of this standard. Consequently, in this standard, these references will be non-sequential. Figure 3 Constituent surface areas of a screw or bolt (see D.2)5) Licensed Copy: shef
22、fieldun sheffieldun, na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3382: Parts 5 & 6:1967 8 BSI 09-1999 The surface area a of an inch length of the threaded shank of the screw or bolt (see Figure 3). The surface area b of an inch length of the unthreaded shank of the screw or
23、 bolt (see Figure 3). NOTEIf the thread is cut, the unthreaded shank will be approximately equal to the basic major diameter. If the thread is rolled, the unthreaded shank will be approximately equal to either the thread effective diameter (rolling diameter) or the basic major diameter. Surface area
24、 values for both basic major diameter and rolling diameter are, where appropriate, given in the tables. The surface area c of the head to which has been added the surface area of the end of the shank (see Figure 3). The total surface area of a screw or bolt may be calculated from the following formu
25、la: Total area = (length of threaded shank a) + (length of unthreaded shank b) + c. The values for area of head of all other screws and bolts given in the tables except hexagon heads, are in respect of slotted and recessed heads. D.3 Nuts Table 7 Table 10 give the surface areas of general purpose nu
26、ts. The effective surface area of a nut for the purposes of electroplating is normally less than its actual geometrical area because of the difficulty in obtaining a uniform distribution of plating deposit over the interior threads, the majority of the deposit on the threads being on the first threa
27、d at each end. For the purposes of this standard, therefore, the calculation of the surface area of a nut has been based on a solid of the shape of the nut but neither drilled nor tapped. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 33
28、82: Parts 5 & 6:1967 BSI 09-19999 Appendix H Strip and weigh method for the determination of group and sample average plating thickness of tin H.1 Thoroughly clean and free each group of items from grease. H.2 Thoroughly dry each group of items. H.3 Weigh each group of items together or in such smal
29、l groups as are appropriate to the maximum capacity of the balance to an accuracy of 1 mg on each weighing. H.4 Totally immerse each group of items in hydrochloric acid (d 1.161.18) and simmer until the tin coating is dissolved, turning each item over in the solution to permit free access of the aci
30、d to all surfaces. H.5 Remove items from the stripping solution immediately the coating is completely dissolved, wash well with water, wipe and immerse in clean acetone or ethanol to remove any trapped water. Dry each item, and re-weigh each group exactly as before. H.6 Deduce the weight of plating
31、for each group by subtraction of the results of the weighings. H.7 Calculate the areas of coatings of the ten or more items in the group from the data given in Table 2 Table 10. H.8 Calculate the group average thickness (assuming a relative density of 7.30 for the tin deposit, i.e. 120 g/in3) from:
32、H.9 Calculate the sample average thickness (for sample, Type 3) from the following formula: NOTE 1For sample, Types 1 and 2, the sample average thickness equals the group average thickness. NOTE 2The thickness of any undercoat should be confirmed by micro-examination. Appendix J Examples of calculat
33、ions of deposit thicknesses of tin on plated components EXAMPLE 1 10-32 UNF Pan Head Screw, 1 in threaded shank. Surface area from Table 3: 0.903 + 0.349 = 1.252 in2 Suppose weight of deposit on 10 pieces is 0.3455 g EXAMPLE2 1 in long in diameter BSF Hexagon Bolt with 1.0 in threaded shank (rolled
34、thread). Surface area from Table 2: 2.151 + 0.630 + 1.659 = 4.440 in2 Suppose weight of deposit on 10 pieces is 1.438 g EXAMPLE 3 Hexagon head bolt M12 40 to BS 3692 (i.e. 12 mm dia, 40 mm long with 30 mm threaded shank) Surface area from Table 6: 17.442 + 3.769 + 11.510 = 32.721 cm2 Suppose weight
35、of deposit on 10 pieces is 1.672 g NOTEMaximum and minimum areas of threads. The figures given in the table of surface areas of threads are according to maximum dimensions allowable in the screw thread standard. Calculations demonstrate that the difference in thickness determinations based on screws
36、 of minimum surface area is not significant. Group average thickness weight of coating (grammes) area of coating in2()120 - - in weight of coating (grammes) area of coating cm2()7.3 - - cm= Sample average thickness sum of all relevant group average thicknesses number of groups - -= Group average thi
37、ckness 0.034 55 1.252120 - -0.000 23 in= 716 Group average thickness 0.1438 4.440120 - -0.000 27 in= Group average thickness 0.1672 32.7217.3 - -0.000 7 cm0.007 mm= Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3382: Parts 5 & 6:1967 10
38、 BSI 09-1999 Appendix K Strip and weigh method for the determination of group and sample average plating thickness of silver K.1 Thoroughly clean and free each group of items from grease. K.2 Thoroughly dry each group of items. K.3 Weigh each group of items together or in such small groups as are ap
39、propriate to the maximum capacity of the balance to an accuracy of 1 mg on each weighing. K.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: K.5 Remove items from the stripping solu
40、tion 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 early stages of the final rinsing. K.6 Remove items from the sulphuric acid, wash well with cold running water, wipe a
41、nd immerse in clean acetone to remove any trapped water. Dry each item, and reweigh each group exactly as before. K.7 Deduce the weight of plating for each group by subtraction of the results of the weighings, or evaluate it from the stripping solutions by a normal method of chemical estimation (e.g
42、. potentiometric titration with a standard sodium chloride solution). K.8 Calculate the areas of coatings of the ten or more items in the group from the data given in Table 2 Table 10. K.9 Calculate the group average thickness (assuming a relative density of 10.5 for the silver deposit, i.e. 172 g/i
43、n3) from: K.10 Calculate the sample average thickness (for sample, Type 3) from the following formula: NOTEFor sample Types 1 and 2, the sample average thickness equals the group average thickness. Appendix L Examples of calculation of deposit thicknesses of silver on plated threaded shanks L.1 1032
44、 UNF, 1 in length of thread. Deposit silver plating thickness range 0.000 200.000 25 in. Surface area (as given in Table 3) = 0.903 in2. EXAMPLE1 Suppose a weight of deposit on 10 pieces is 0.3106 g EXAMPLE 2 Suppose a weight of deposit on 10 pieces is 03883 g L.2 in UNC, 1 in length of thread. Depo
45、sit silver plating thickness range 0.000 250.000 30 in. Surface area (as given in Table 3) = 2.401 in2. Sulphuric acid (d 1.84): 19 parts by volume Nitric acid(d 1.42):1 part by volume Temperature:60 C70 C Group average thicness weight of coating grammes() area of coating in2()172 - - in weight of c
46、oating grammes() area of coating cm2()10.5 - - cm= Sample average thickness sum of all relevant group average thicknesses number of groups - -= Group average thickness 0.031 06 0.903172 - -0.000 20 in= Group average thickness 0.038 83 0.903172 - -0.000 25 in= Licensed Copy: sheffieldun sheffieldun,
47、na, Wed Nov 29 03:54:16 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 3382: Parts 5 & 6:1967 BSI 09-199911 EXAMPLE 1 Suppose weight of deposit on 10 pieces is 1.0324 g EXAMPLE 2 Suppose weight of deposit on 10 pieces is 1.2389 g NOTEMaximum and minimum areas of threads. The figures given in the table of surface areas of threads are accor