1、. . . . . . . . . . . . . l. l . . . . . . . . . I . . . . . AmerdmeratNo.2,11A1966 to B.S. 450 : 1958 Machine screws and machine screw nuts (BSW and BSF threads) BSI BS*450 58 m 1624669 0038458 8 m BRITISH STANDARD SPECIFICATION MACHINE SCREWS AND MACHINE SCREW NUTS A (l3.S.W. AND B.S.F. THREADS) O
2、BSOLESCENT B.S. 450 : 1958 Incorporating amendment issued January 1966 (PD 5730) and September 1974 (AMD 1561) BRITISH STANDARDS INSTITUTION Incorporated by Royal Charter British Standards House, 2 Park Street, London, W1Y 4AA Telegrams: Standards London W1 Telephone: 01-629 9OOO UDC 621.882.082.3 B
3、SI BS*450 58 m Lb2Llbb7 00381.157 T m B.S. 450 : 1958 THIS BIUTISH STANDARD, having been approved by tbe Mechanical Engineering Industry Standards Committee and endorsed by the Chairman of the Engineering Divisional Council, was published under the authority of the General Council on 30th June, 1958
4、. First published May, 1932. First revision June, 1958. The Institution desires to call attention to the fact that this British Standard does not purport to include all the necessq provisions of a contract. In order to keep abreast of progress in the industries concerned, British Standards are subje
5、ct to periodical review. Suggestions for improvements will be recorded and in due course brought to the notice of the committees charged with the revision of the standards to which they refer. A complete list of British Standards, numbering over 5000, indexed and cross-indexed for reference, togethe
6、r with an abstract of each standard, will be found in the Institutions Yearbook. gis standard makes reference to the following British Standards : B.S. 57. B.A. screws, bolts, nuts and plain washers. B.S. 84. Parallel screw threads of Whitworth form. B.S. 1473. Wrought aluminium and aluminium alloys
7、. Rivet, bolt and screw stock for forging. B.S. 1475. Wrought aluminium and aluminium alloys. Wire. B.S. 1476. Wrought aluminium and aluminium alloys. Bars, B.S. 2827. Machine screw nuts, pressed type, (B.A. and B.S. 4183 : 1967 Metric screws and machine screw nuts - rods and sections. Whitworth for
8、m threads). metric sizes. British Standards are revised, when necessary, by the issue either of amendment slips or of revised editions. It is important that users of British Standards should ascertain that they are in possession of the latest amendments or editions. The following BAI. references rel
9、ate to the work on this rtandard :- Committee deranca MEE/60. Draft for comment CW(MBE) 7W3 2 . r 7 BSI BS*450 58 M Lb24bb7 0038460 b B.S. 450 : 1958 COlVmNTs Co-operating organizations 4 Foreword 5 Page SPECIHCATION 1. scope 6 2. Material 6 3. Terminology 7 4. Dimensions 7 5. Heads of screws 7 6. L
10、ength of screws 8 7. Ends of screws 8 8. Screw threads 10 9. Length of thread on screws 10 IO. Diameter of unthreaded shank on screws 10 TABLES l. Dimensions of header points 9 2. Slatted and recessed 90“ countersunk head screws 13 3. Slotted and recessed 90“ raised countersunk head screws 15 4. Slo
11、tted and recessed round head screws 16 5. Slotted and recessed pan head screws 18 6. Slotted cheese head screws 21 7. Recessed raised cheese head screws 23 8. Slotted and recessed mushroom head screws 25 APPENDICES A. Non-preferred and non-standard machine screws and machine screw nuts 27 B. Flushne
12、ss gauge for stotfed and recessed 90“ countersunk head screws 35 C. Standard sizes of machine screws 36 D. Recess penetration gauging 47 E. Formulae for dimensions 50 F. Metricslot widths 57 3 T I BSI BSmltSO 58 W Lb2Llbb7 0038“tbL B.S. 450 : 1958 CO-OPERATING ORGANIZATIONS The Mechanical Engineerin
13、g Industry Standards Committee, under whose supervision this British. Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations :- Air Ministry Associated Offices Technical Committee Association of Consulting Engineers (I
14、ncorporated) British Chemical Plant Manufacturers Association British Compressed Air Society +Admiralty +British Electrical and Allied Manufacturers Association +British Engineers Association +British Internal Combustion Engine Manufacturers Association British Iron and Steel Fedcration British Rail
15、ways, The British Ibnsport Commission +Crown Agents for Oversea Governments and Administrations British Gear Manufacturers Association Central Electricity Authority and Area Boards D.S.I.R.-Mechanical Engineering Research Laboratory Electricity Council, the Generating Board and the Area Boards in En
16、gineering Equipment Users Association Gas Council Institute of Marine Engineers Institute of Petroleum Institution of Civil Engineers Institution of Gas Engineers Institution of Heating and Ventilating Engineers Institution of Mechanical Engineers Institution of Mechanical Engineers (Automobile Divi
17、sion) Institution of Production Engineers +Locomotive and Allied Manufacturers Association of Great Britain England and Wales +High Commission of India Ministry of Labour and National Service (Factory Inspectorate) Ministry of Power Ministry of Supply Ministry of Transport and Civil Aviation Ministr
18、y of Works National Physical Laboratory (D.Y.I.R.) National Coal Board +RadioIndustry Council War Office The Government deparfments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the Committee entrusted
19、 with the preparation of this standard :-. Bright Bolt and Nut Manufacturers Association Bright Steel Bar Association British Constructional Steelwork Association Cold Headed Heat Treated Bolt Association British Cycle and Motor Cycle Industries Association Council of British Manufacturers of Petrol
20、eum Equipment Electronic Engineering Association Institute of Iron and Steel Wire Manufacturers Institution of Naval Architects Machine Tool Trades Association Metal Thread Screw Manufacturers Association (Rolled Screw Section) Metal Thread Screw Manufacturers Associafion (Turned Screw Section) Soci
21、ety of Motor Manufacturers and Traders Ltd. Post Office Washer Manufacturers Association 4 t This British Standard for machine screws and machine screw nuts with B.S.W. or B.S.F. threads was prepad under the authority OP the Mechanical Engineering Industry Standards Committee, and was the continuing
22、 use of such screws with B.S.W. and B.S.F. threads during the transition period precluded the withdmwal sf B.S. 450, and it was clearly undesirable Ehat two standards for comparable products, is. B.S. 1981 and B.S. 450, should exist side by sida but contain general requirements which differed from e
23、ach other. The Chrunittee ascordingly felt that it was right to sontime with the preparation of an up-to-date version of the latter standard. The scope of the standard has bn extended to include all the. various types of heads in 60mpn0 use h both slotted and recessed form, and the general rqairemen
24、ts are in most cases sinnilar to those in B.S. 1981, Development is continually taking pkse, however, in methods of manu- facture, and further advances in established practice have hen recognized in drdthg the text of this standard. 10 will be noid that dimensions for several sizes sf screws blow W
25、in. md details of hexagon ordinary nuts and lock nuts in sim from He in. to 7/52 in. inclusive have bn given in m appendix. It has long ken the BSI Bs*K450 58 W Lb24bb9 00384b3 L W B.S. 450 : 1958 practice to discourage the use of these fasteners with B.S.W. or B.S.F. threads, and to recommend the s
26、ubstitution of the nearest equivalents from the B.A. range. Although their use is still strongly deprecated, however, the number of enquiries relating to these fasteners received both by the Institution and by the manufacturers suggested that it would be advisable to provide information in this stan
27、dard and thus eliminate the production of numbers of these screws and nuts possibly differing from each other only in some small particular. SPECIFICATION SCOPE 1. The provisions of this British Standard are applicable to both ferrous and non-ferrous screws and nuts having B.S.W. or B.S.F. threads.
28、General dimensions and requirements are given for countersunk, raised countersunk, round, pan, cheese and mushroom head screws with slotted heads, and countersunk, raised countersunk, round, pan, raised cheese and mushroom head screws with recessed heads. General dimensions for a restricted range of
29、 non-standard sizes of some of the above types of screws, together with dimensions of hexagon head screws and hexagon precision nuts in sizes below W in. are given in an appendix. Other appendices relate to a suitable head flushness gauge for countersunk head screws, a method of checking recess pene
30、tration with standard gauge points, the formulae from which the dimensions are derived, and tables of standard sizes. NOTE 1. Round head screws appeared in the 1932 edition of B.S. 450 and they are therefore included in this revised standard. It is considered, however, that pan head screws provide f
31、or most of the applications in which round head screws are normally used and it is recommended that they be regarded as preferred since their shape enables them to offer better slot engagement. NOTE 2. Machine screw nuls, pressed type (B.A. and Whitworth form threads) are covered by B.S. 2827. 2. Th
32、e material from which the screws and nuts are manufactured shall have a tensile strength of not less than the following : Brass 20 tonslsq. in. Aluminium alloy 20 tonslsq. in. MATERIAL Steel 25 tonslsq. in. These minimum tensile strengths may be taken as being applicable to the finished products. (S
33、ee Note 1 ,) The failing load of a nut on assembly depends not only upon the tensile strength of the material but also upon the thickness of the nut and the type of thread. If the purchaser requires the screws and nuts to be manufactured from steel or brass of a higher tensile strength, or of anothe
34、r material, he shall specify the tensile strength of the material. 6 c BSI BSm450 58 m Lb24bb7 0038Llb4 3 I B.S. 450 : 1958 Screws to this standard are not normally subjected to tensile test, and where this is required the purchaser shall state so in his enquiry and order. NOTE. The choice of alumin
35、ium alloy should normally be left to the manufacturer, but some suitable alloys satisfying the requirements are given below. Any alloy currently covered by British Standards 1473,1475 or 1476, with a tensile strength of not less than 20 tonslsq. in. is also suitable. For screws and nuts turned from
36、wire : B.$. 1475 : 1955. Wrought aluminium and aluminium alloys. Wire. HG14 T HG15 W or WP. For screws and nuts turned from bar :. B.S. 1476 : 1955. Wrought aluminium and aluminium alloys. Bars, rods and sections. HE11 WP HE14 T HE15 W or WP For screws up to and including 3/8 in. diameter cold-heade
37、d from wire: B.S. 1473 : 1955. Wrought aluminium and aluminium alloys. Rivet, bolt and screw stock for forging NB LENGTH OF THREAD ON SCREWS 9. Screws 2 in. long and under shall be threaded as far as possible up to the head. The length of unthreaded shank under the head shall not exceed twice the pi
38、tch and 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 : u. The junction of the basic major diameter and the countersunk portion of head on countersunk and raised countersunk heads, and 6. the underside of the head on ot
39、her types of heads. The nut shall have screw threads conforming to B.S. 84, Normal Screws over 2 in. long shall have a minimum length of thread of Class limits and shall not be countersunk. 1% in. DIAMETER OF UNTHREADED SHANK ON SCREWS 10. The diameter of the unthreaded portion of the shank on screw
40、s shall not exceed the basic major diameter of the screw thread and shall not be less than the minimum effective diameter of the screw thread. Where it is essential that the diameter of the unthreaded portion of the shank shall not be below the minimum major diameter of the thread this should be sta
41、ted by the purchaser. NOTE. The diameter of the unthreaded portion of shank is closely associated with the method of manufacture ; it will generally be nearer the maximum major diameter of the thread for turned screw8 and nearer the minimum effective diameter for those produced by cold heading, r 10
42、 BSI BS*450 58 I L624667 O038468 O B.S. 450 : 1958 ri Previous page is blank 12 I i ES1 BS*450 58 I L624669 00384b7 2 I 1 B.S. 450 : 1958 1 B m .m “ “ -5 n 3- .ggg 000 gg NN(D ddN O00 O00 O00 mat- 3s .E000 o00 8sg 2: gl+g Md-m O00 O00 O00 m W m 13 14 BSI BS*450 58 3624669 0038473 O m B.S. 450 : 1958
43、 II I I I - i .- i 11 S“ omm om0 BSI BS*450 58 m Zb24bb7 0038472 2 m B.S. 450 : 1958 4 Length Y I- I% in. min - “B fH “ !* A Min unthreaded shank dia (see clause IO) Fig, 8. Screws 2 in. long and under Fig. 9. Screws over 2 in. long TABLE 4. SLOITED ROUND HEAD SCREWS 1 I 2 13 14 15.1 6 17 18 19 1011
44、1213/14 General . I Slotted head Slot A “- in. in. * The shape of the head shall closely approximate to a half ellipse. -Radius G (struck off the under- side of the head) must pass through Diameter.A and touch Radius F. t Sizes marked thus are non-preferred and should be avoided whenever possible. 3
45、 To permit tlie use of Me in. bar. the minimum head diameter may. by arrangement between pur- chaser and manltfaCturer, be 0.309 in. . 16 F . ES1 BS*450 58 I 1624669 0038473 4 m B.S. 450 : 1958 Length I u IMax unthraaded shank dia (See clause IO) Length c r # I - T 41 ci Hg. 11. Screws 2 h. long and
46、 m I uuuer u (Min unthreaded shank dia (See clause IO) Fig. 12. Screws over 2 in. long TABLE 5. SLOITED AND RECESSED General I Number i Diameter i under head j Radius Nom. Basic of threads max. i min. I max. I I-“ “ in. l/g 0.125 O in. 95s 0.187 5 %/32 0.218 8 0.2500 %o 0.312 5 s/g 0.375 O -,“ - in.
47、 f in. in. 40 - 0.245 , 0.231 0.010 - B$ , 0,425 0.407 0.015 24 322 0.373 0.357 , 0.015 -i- i ! i 20 26 . 0.492 . 0.4738 0.031 18 22 0.615 0.594 0.031 16 20 , 0.740 0.716 0.031 14 18 0.863 0.838 0.031 12 16 0.987 0,958 0.031 - P _ max. 0.020 in. 0.025 0.025 0.040 O*W5 0.045 - 0.050 0.050 6/g 0.625 O
48、 11 14 1.125 1.090 0.031 0.055 W 0.750 O 10 12 1.250 1,209 0.031 0.060 I Slotted head of head Depth B ,I :j i I! * These dimensions refer to the penetration of standard gauge points used with special penetration t The diameter S is measured at the points of intersection between the sides of the rece
49、ss, and the S To permit the use of 12 mm bar the minimum head diameter may, by arrangement between the Sizes marked thus are non-preferred and should be avoided whenever possible. r 18 Previous page I max. in. 0.075 0.110 0.125 - 0.144 0.178 0-212 0.247 0.281 0.315 0.350 I - min. 0.065 in. 0.099 0.112 0.130 0.162 0.195 0.227 0.260 l- I I ! j - Radius of head F nom. 0.044 in. 0.061 0,078 0.087 0.099 0.143 0.148 0.169 0.293 I 0.189 0.325 1 0.210 0.419 ; 0,390 I 0.25
