1、BRITISH STANDARD BS57:1951 Incorporating Amendment Nos.1, 2 and 3 Specification for B.A. Screws bolts and nuts UDC 621.882.082.1(42)BS57:1951 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committee and endorsed by the chairman ofthe Engineering Divisional
2、 Council, was published under theauthority of the General Council on 31 March1951 BSI09-1999 First published1920 First revision September1944 Second revision March1951 ISBN 0 580 00920 3 Co-operating organizations The Mechanical Engineering Industry Standards Committee, under whose supervision this
3、British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Admiralty* Institute of Petroleum Air Ministry Institution of Civil Engineers Association of Consulting Engineers Institution of Gas Engineers (Incorporat
4、ed) Institution of Heating and Ventilating Associated Offices Technical Committee Engineers British Chemical Plant Manufacturers Institution of Mechanical Engineers Association Institution of Mechanical Engineers British Compressed Air Society (Automobile Division) British Electrical and Allied Manu
5、facturers Institution of Production Engineers* Association* Locomotive Manufacturers Association* British Engineers Association* Machine Tool Trades Association* British Internal Combustion Engine Ministry of Fuel and Power Manufacturers Association* Ministry of Labour and National Service British I
6、ron and Steel Federation* (Factory Department) British Railways, The Railway Executive* Ministry of Supply* Crown Agents for the Colonies* Ministry of Transport* Department of Scientific and Industrial Ministry of Works Research Office of the High Commissioner for India* Engineering Equipment Users
7、Association* War Office Institute of Marine Engineers The Government departments and scientific organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Aircraft Bolt and
8、Nut Manufacturers Metal Thread Screw Manufacturers Association Association (Rolled Screw Section) Bright Bolt and Nut Manufacturers Metal Thread Screw Manufacturers Association Association (Turned Screw Section) Bright Steel Bar Association National Physical Laboratory British Constructional Steelwo
9、rk Association Oil Companies Materials Committee British Cycle and Motor Cycle Manufacturers Radio Industry Council and Traders Union Ltd Society of British Aircraft Constructors British Steel Wire Industries Association Society of Motor Manufacturers and Cold Headed Heat-treated Bolt Association Tr
10、aders Ltd. Council of British Manufacturers of Petroleum Telecommunications, Engineering and Equipment Manufacturing Association General Post Office Washer Manufacturers Association Institution of Naval Architects Amendments issued since publication Amd. No. Date of issue Comments 4329 October 1961
11、5901 August 1966 1528 August 1974 Indicated by a sideline in the marginBS57:1951 BSI 09-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii Section 1. Screws, bolts and nuts 1 Scope 1 2 Method of manufacture 1 3 Material 1 4 Dimensions 1 5 Length of screws and bolts 1 6 En
12、ds of screws and bolts 1 7 Screw threads 2 8 Length of thread on screws and bolts 2 9 Chamfering and washer-facing 3 Section 2. Plain washers Deleted Appendix A Special types of screws not normally stocked 14 Appendix B Approximate proportions 16 Appendix C Metric slot widths 16 Figure 1 Alternative
13、 types of ends permissible on screws and bolts 2 Figure 2 Cheese head screw 4 Figure 3 Round head screw 5 Figure 4 Countersunk head screw 6 Figure 5 Raised-countersunk head screw 7 Figure 6 Hexagonal headed screw 8 Figure 7 Hexagonal headed bolt 8 Figure 8 Washer faced head 8 Figure 9 Hexagonal ordi
14、nary nut 9 Figure 10 Hexagonal thin (or lock) nut 9 Figure 11 Hexagonal ordinary nut 9 Figure 14 Raised cheese (fillister) head screw 14 Figure 15 Connection head screw 15 Table 1 Cheese head screws 4 Table 2 Round head screws 5 Table 3 Countersunk head screws 6 Table 4 Raised-countersunk (instrumen
15、t) head screws 7 Table 5 Hexagonal headed screws and bolts 8 Table 6 Hexagonal ordinary (or full) and thin (or lock) nuts 9 Table 7 Lengths of steel and brass cheese and countersunk head B.A. screws (screwed to head) 10 Table 8 Lengths of steel and brass round head B.A. screws (screwed to head) 11 T
16、able 9 Lengths of steel and brass raised-countersunk (instrument) head B.A. screws (screwed to head) 12 Table 10 Lengths of steel hexagonal head B.A. screws (screwed to head) and bolts (2 B.A. only) 13 Table 13 Raised cheese (fillister) head screws 14 Table 14 Connection head screws 15 Table 15 Slot
17、 widths 17 NOTEThe requirements for washers in this standard have been superseded by the publication of BS3410, “Metal washers for general engineering purposes”, to which reference should now be made.BS57:1951 ii BSI 09-1999 Foreword This standard requires reference to the following: BS93:1951, Brit
18、ish Association (B.A.) screw threads, with tolerances for sizes0 B.A. to16 B.A. BS4183:1967, Machine screws and machine screw nuts metric series. This British Standard was first issued in1920. The provisions of that edition related solely to the dimensions of the heads of the various types of screws
19、 and the dimensions of ordinary hexagon nuts. When the first revision of the standard was published in1944 its scope was extended to include requirements for the complete dimensions of screws, bolts and nuts; in addition, dimensions for lock nuts and for two sizes of washers were given. The edition
20、was issued as a War Emergency British Standard and took into account recommendations, contained in instructions issued by the Ministry of Supply, which indicated those types, sizes and lengths of small screws and bolts regarded as standard production. General dimensions for all the common types and
21、sizes of B.A. screws bolts and nuts were included in the standard, but the dimensions for types not recognized as standard were given in an Appendix. The tables in the body of the specification designated selected sizes as “standard” and all other sizes as “specials”. A table of “Standard lengths of
22、 steel and brass B.A. bolts and screws for wartime production” was given in an Appendix. The War Emergency edition has now been reviewed in the light of present-day conditions and, whilst the principles stated above have been largely adopted in the present revision, certain modifications which more
23、recent experience has shown to be desirable have been incorporated. There has been some rearrangement of the tables of general dimensions, including the transfer of the table of dimensions for “Raised-countersunk (instrument) head screws and bolts” from the Appendix to the body of the standard. The
24、ranges of nominal sizes given in these tables are now designated “Preferred,” “Second choice” and “Not normally stocked”; the table of standard lengths has been reviewed and tables are now included in the standard relating to each type of screw and showing the lengths in which each size is normally
25、stocked and other lengths which may be regarded as standard, although they are not normally stocked. Finally, since the production of B.A. bolts is very small compared with that of B.A. screws, the title of the standard has been suitably revised. A British Standard does not purport to include all th
26、e necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, p
27、ages1 to17 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS57:1951 BSI 09-1999 1 Section 1. Screws, bolts and nuts 1 Scope Section1 of this British Standard speci
28、fies requirements and dimensions for both ferrous and non-ferrous screws, bolts and nuts. 2 Method of manufacture Screws and bolts may be either turned from bars or forged. 3 Material The material from which the screws, bolts and nuts are manufactured shall have an ultimate tensile stress of not les
29、s than the following: If the purchaser requires the screws, bolts and nuts to be manufactured from steel or brass of a higher tensile stress, or of another material, he shall specify the ultimate tensile stress of the material. NOTEThe choice of alloy should normally be left to the manufacturer, but
30、 among suitable light alloys satisfying the requirement are the following: For screws, bolts and nuts turned from wire or from the bar: BS1475 or BS1476 respectively: 4 Dimensions The screws, bolts and nuts shall conform to the dimensions and tolerances given in Table 1, Table 2, Table 3, Table 4, T
31、able 5, Table 6, Table 13 and Table 14, and Clauses5, 6, 7, 8 and9. The screw heads shall be concentric with the shank. The slots shall be clean and free from burrs and, on visual inspection, shall appear to be closely co-incident with the centre line of the head. NOTEScrews and bolts turned from ba
32、rs can be supplied with a smaller radius under the head if specially ordered. 5 Length of screws and bolts a) Countersunk heads. The nominal length shall be the distance from the upper surface of the head to the extreme end of the shank, including any chamfer or radius. b) Raised-countersunk (instru
33、ment) heads. The nominal length shall be the distance from the upper surface of the head (excluding the raised portion) to the extreme end of the shank, including any chamfer or radius. c) Hexagonal, round, cheese, raised-cheese (fillister), and connection heads. The nominal length shall be the dist
34、ance from the underside of the head to the extreme end of the shank, including any chamfer or radius. NOTEThe nominal lengths of screws normally stocked are given in Table 7, Table 8, Table 9 and Table 10. Bolts (screwed part way) are not normally stocked but should be ordered to the lengths given i
35、n Table 7, Table 8, Table 9 and Table 10. d) Tolerance on length. The permissible tolerance on the nominal length of screws and bolts shall be as follows: 6 Ends of screws and bolts a) Cut threads. The ends of screws and bolts with cut threads may, at the option of the manufacturer, be finished with
36、 either a flat chamfer with a90 included angle to a depth slightly exceeding the depth of thread, or with a radius approximately equal to1 times the nominal diameter of the shank. b) Rolled threads. When screws and bolts are made with rolled threads the lead formed at the end of the screw or bolt by
37、 the thread-rolling operation may be regarded as providing the necessary chamfer to the end and no other machining operation is necessary, unless the purchaser, in his enquiry and order, has specified that the ends shall be finished as in Clause6 a) above. NOTEFor convenience, one type of end only i
38、s illustrated in the Figures at the head of Table 1 to Table 5 inclusive, and Table 13 and Table 14. The three alternative types of end permissible are shown in Figure 1 below. Steel 25tons/sq.in. Brass 20tons/sq.in. Aluminium alloy 20tons/sq.in. BS1475, “Aluminium and aluminium alloy wire for gener
39、al purposes.” H.G. 14. T H.G. 15 (Condition W or WP) BS1476, “Aluminium and aluminium alloy rods, bars and sections for general purposes.” H.E. 11. WP H.E. 14. T H.E. 15 (Condition W or WP) For screws and bolts cold headed from wire: BS1475, “Aluminium and aluminium alloy wire for general purposes.”
40、 N.G. 6. M H.G. 14. T H.G. 15 (Condition W or WP) Nominal length Tolerance Up to and including (in. +0.01 in.0. Above ( in., up to and including “ in. +0.02 in.0. Above “ in. + 1 /32in.0.BS57:1951 2 BSI 09-1999 7 Screw threads a) Screws and bolts. The screw threads may be either cut or rolled, at th
41、e option of the manufacturer. Limits and tolerances shall be as specified for normal class bolts in BS93:1951, “British Association screw threads.” Screws and bolts with close class threads are not normally stocked and should not be ordered, except for special work where refined accuracy of pitch an
42、d thread form is particularly required. If the limits and tolerances in respect of the screws and bolts are to be as specified for close class bolts in BS93:1951, this shall be stated by the purchaser in his enquiry and order. b) Nuts. The limits and tolerances of the screw threads shall be as speci
43、fied in BS93:1951. 8 Length of thread on screws and bolts a) Screws: countersunk and raised-countersunk heads. These shall be threaded right up to the head. b) Screws: hexagonal, round, cheese, raised-cheese (fillister) and connection heads. These shall be threaded to leave a limited length of unthr
44、eaded shank under the head. The length of unthreaded shank is defined as the distance from the leading face of a nut which has been screwed as far as possible on to the screw by hand to the underside of the head. The nut shall have threads as specified in Clause7 b) and shall not be countersunk. The
45、 length of unthreaded shank shall not exceed the following: c) Bolts. The length of thread on bolts shall be the distance from the end of the bolt (including any chamfer or radius) to the leading face of a nut which has been screwed as far as possible on to the bolt by hand. The nut shall have threa
46、ds as specified in Clause7 b) and shall not be countersunk. Figure 1 Alternative types of ends permissible on screws and bolts Nominal length of screw Length of unthreaded shank Up to and including5times thediameter. Not to exceed1 times the pitch. Greater than5 times the diameter. Not to exceed2 ti
47、mes the pitch.BS57:1951 BSI 09-1999 3 The length of thread shall be not less than three times the nominal diameter of the bolt. 9 Chamfering and washer-facing a) Hexagonal headed screws and bolts. These shall have a chamfer of approximately30 on their upper faces. The underside of the head may, at t
48、he option of the manufacturer, be finished flat, or in the case of sizes0 to6 B.A. inclusive, have a washer-face. b) Hexagonal ordinary (or full) nuts. These shall have a chamfer of approximately30 on both faces, but sizes13 B.A. and smaller may, at the option of the manufacturer, be chamfered on on
49、e face only. c) Hexagonal thin (or lock) nuts. These shall have a chamfer of approximately30 on both faces.BS57:1951 4 BSI 09-1999 Table 1 Cheese head screws Figure 2 Cheese head screw 1 2 3 4 5 6 7 8 9 10 11 12 B.A. No. Diameter of shank and major diameter of thread Diameter of head Depth of head Radius under head Slot Width Depth D A B R H J max. max. min. max. min. max. max. min. nom. mm. in. in. in. in. in. in. in. in. in. Preferred 2 4 6 8 10 12 4.7 3.6 2.8 2.2 1.7 1.3 0.185 0.142 0.110 0
