1、BRITISH STANDARD CONFIRMED FEBRUARY1988 BS2470:1973 (Reprinted, incorporating Amendment No.1) Specification for Hexagon socket screws and wrench keys Inch series UDC 666.71/.72:691.421BS2470:1973 This British Standard, having been approved by the MechanicalEngineering IndustryStandards Committee,was
2、 published underthe authorityof the Executive Board on 15 June1973 BSI 10-1999 First published June1954 First revision June1973 The following BSI references relate to the work on this standard: Committee references MEE/60/3 and MEE/60 Draft for comment68/23846 ISBN 0 580 07139 1 Co-operating organiz
3、ations The Mechanical Engineering Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: The Government departments and scientific and industrial orga
4、nizations 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: Associated Offices Technical Committee Engineering Equipment Users Association* Association of Consulting Engineers Ga
5、s Council* Association of Hydraulic Equipment Institution of Civil Engineers Manufacturers Ltd.* Institution of Gas Engineers* Association of Mining Electrical and Institution of Heating and Ventilating Mechanical Engineers Engineers British Compressed Air Society Institution of Mechanical Engineers
6、 British Electrical and Allied Manufacturers Institution of Mechanical Engineers Association* (Automobile Division) British Gear Manufacturers Association Institution of Plant Engineers British Internal Combustion Engine Institution of Production Engineers* Manufacturers Association Locomotive and A
7、llied Manufacturers British Mechanical Engineering Confederation Association of Great Britain* British Pump Manufacturers Association London Transport Executive British Steel Industry* Machine Tool Trades Association* Crown Agents for Oversea Governments and Ministry of Defence Administrations Minis
8、try of Defence, Army Department Department of Employment (H.M. Factory National Coal Board* Inspectorate) National Physical Laboratory (Department of Department of the Environment* Trade and Industry) Department of Trade and Industry Process Plant Association Department of Trade and Industry Nationa
9、l Royal Institute of British Architects Engineering Laboratory Telecommunications Engineering Electricity Council, the Central Electricity Manufacturing Association Generating Board and the Area Boards in Water-tube Boilermakers Association England and Wales* Black Bolt and Nut Association of Instit
10、ute of Iron and Steel Wire Manufacturers Great Britain Ministry of Aviation, Supply Department British Bolt Nut Screw and Rivet Federation Ministry of Defence, Navy Department British Constructional Steelwork Association Precision Bolt and Nut Institute British Railways Board Rolled Thread Screw Ass
11、ociation Constructional Steel Research and Scientific Instrument Manufacturers Development Organization Association of Great Britain Council of British Manufacturers of Petroleum Society of Motor Manufacturers and Traders Equipment Socket Screw Manufacturers Association Electronic Engineering Associ
12、ation Washer Manufacturers Association of Fasteners and Turned Parts Institute Great Britain Amendments issued since publication Amd. No. Date of issue Comments 4127 November 1983 Indicated by a sideline in the marginBS2470:1973 BSI 10-1999 i Contents Page Co-operating organizations Inside front cov
13、er Foreword iii 1 General 1 1.1 Scope 1 2 Hexagon socket screws 1 2.1 Materials 1 2.2 Finish 1 2.3 Dimensions 1 2.4 Head diameter 1 2.5 Length of socket screws 1 2.6 Tolerance on length 1 2.7 Ends of socket screws 2 2.8 Screw threads 2 2.9 Radius under head 2 2.10 Length of thread 2 2.11 Concentrici
14、ty and straightness 3 2.12 Dimensions of hexagon sockets 4 3 Hexagon wrench keys and bits 21 3.1 Material 21 3.2 Finish 21 3.3 Dimensions 21 3.4 Ends of keys 21 3.5 Torque test 21 3.6 Application 21 Appendix A Mechanical properties of finished alloy steel hexagon socket screws and wrench keys 24 App
15、endix B Dimensioning of countersunk head screws 26 Appendix C Terminal length increments for socket screws 27 Figure 1 Alternative types of cup point and socket permissible with hexagon socket set screws with ISO inch (Unified), BA, BSW and BSF and G(BSPF) threads 15 Table 1 Option1 for thread lengt
16、h and grip lengths of cap screws having UNC, UNF, BSW, BSF and BA threads 5 Table 2A Dimensions of hexagon socket head cap screws, ISO inch (Unified) threads 8 Table 2B Dimensions of hexagon socket head cap screws, BSW and BSF threads 9 Table 2C Dimensions of hexagon socket head cap screws, BA threa
17、ds 10 Table 3 Dimensions of hexagon socket countersunk head screws with ISO inch (Unified) threads 11 Table 4 Dimensions of hexagon socket button head screws with ISO inch (Unified) threads 12 Table 5 Hexagon socket head shoulder screws (stripper bolts) with ISO inch (Unified) and BSW/BSF threads 13
18、 Table 6A Dimensions of hexagon socket set screws with ISO inch (Unified) threads 16 Table 6B Dimensions of hexagon socket set screws with BSW and BSF threads 17BS2470:1973 ii BSI 10-1999 Page Table 6C Dimensions of hexagon socket set screws with BA threads 18 Table 6D Dimensions of hexagon socket s
19、et screws with G(BSPF) threads 19 Table 7 Dimensions of hexagon sockets 20 Table 8 Dimensions of hexagon wrench keys 22 Table 9 Applicability of hexagon wrench keys to various socket screw types and sizes 23 Publications referred to Inside back coverBS2470:1973 BSI 10-1999 iii Foreword The first iss
20、ue of BS2470, in1954, included hexagon socket screws with Unified threads in sizes 1 / 4in and over, the general dimensions of which were the same as the American specification then current. Since then the American specification has been revised, the two most important changes being the increase of
21、the head diameter of cap screws and the adoption of new thread length formulae which results in shorter thread lengths on long length cap screws. In this revision the head diameters of cap screws are unchanged because of the need to maintain interchangeability with screws to the1954 edition since ho
22、les counterbored for the smaller head would not accommodate the revised American head diameters. The minimum thread lengths resulting from the revised United States thread length formula have been adopted for the optional thread lengths now shown together with most of the minor changes in the Americ
23、an specification, including changes in certain tolerances to bring them in line with current manufacturing practices. Other changes are the inclusion of the Unified numbered series and the80 countersunk and button heads with Unified threads. Hexagon socket screws with the obsolescent BSW, BSF and BA
24、 threads are retained in this revision although at some time they will become obsolete in view of the current recommendation that first preference should be given to ISO metric screw threads. A British Standard does not purport to include all the necessary provisions of a contract. Users of British
25、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 toiv, pages1to28, an inside back cover and a back cover. This s
26、tandard 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.iv blankBS2470:1973 BSI 10-1999 1 1 General 1.1 Scope This British Standard specifies requirements for hexagon socket screws with ISO Inch (
27、Unified) BSW, BSF, G(BSPF) and BA threads and to wrench keys for use with them. Section2 gives dimensions, tolerances and general requirements for cap screws, countersunk head screws, button head screws, shoulder screws (stripper bolts) and set screws. Section3 gives dimensions, tolerances and requi
28、rements for wrench keys. Appendices relate to mechanical properties, nominal length increments and the method of dimensioning countersunk head screws. NOTEThe titles of British Standards referred to in this standard are listed on the inside back cover. 2 Hexagon socket screws 2.1 Materials Steel hex
29、agon socket screws shall be manufactured from high grade alloy steel, hardened, quenched in oil and tempered to give the mechanical properties specified inAppendix A. NOTEHexagon socket screws in any material other than that specified are subject to agreement between the manufacturer and the purchas
30、er. 2.2 Finish Hexagon socket screws shall be cleanly finished and free from defects. High grade alloy steel hexagon socket screws shall have a blue-black heat treatment, or chemical black oxide finish with the exception of the shoulder or body of socket head shoulder screws, which shall have a brig
31、ht ground finish. Where hexagon socket screws are required to be plated, the type and thickness of coating shall be specified by the purchaser in his enquiry and order. BS3382 specifies requirements for electroplated coatings on threaded components. 2.3 Dimensions Hexagon socket screws, plated or pl
32、ain finish, shall conform to the dimensions and tolerances given inTable 2 toTable 6 and2.4 to2.9. 2.4 Head diameter 2.4.1 Cap and shoulder screws. Heads may be plain or knurled at the option of the manufacturer unless otherwise specified. For knurled screws the diameter measured over the top of the
33、 knurl shall not exceed the maximum specified in Table 2A,Table 2B,Table 2C andTable 5 and the diameter of the head before knurling or the unknurled section of head shall be not less than the minimum specified inTable 2A,Table 2B,Table 2C andTable 5. 2.4.2 80 Countersunk head screws. The maximum sha
34、rp values given for82 /80 countersunk heads inTable 3 are theoretical values only as it is not practicable to make the edge of the head sharp (seeAppendix B). 2.5 Length of socket screws 2.5.1 Cap screws and button head screws. The length shall be the distance from the underside of the head to the e
35、xtreme end of the shank, including the chamfer. 2.5.2 Countersunk head screws. The length shall be the distance from the top of the head to the extreme end of the shank, including the chamfer. 2.5.3 Shoulder screws. The length shall be the distance from the underside of the head to the end of the sh
36、oulder or body, excluding the threaded end. 2.5.4 Set screws. The length, for all types of point, shall be the length overall, including the chamfer at the socket end and the point. Unless otherwise specified cup point screws shall be supplied. NOTEFor details of nominal length increments seeAppendi
37、x C. 2.6 Tolerance on length The permissible tolerance on length shall be as follows: 1) Cap screws, countersunk head screws and button head screws Length Tolerance in in Up to and including1 Over1 up to and including6 Over6 0.016 0.031 0.062BS2470:1973 2 BSI 10-1999 2) Shoulder screws (length of sh
38、oulder) 0.005 in 3) Set screws 2.7 Ends of socket screws 2.7.1 Cap screws, countersunk head screws, button head screws and shoulder screws. The end shall be flat or slightly concave and chamfered. The flat shall be normal to the axis of the screw and the included angle of the chamfer shall be approx
39、imately90 . The chamfer shall extend slightly below the root of the thread and the edge between the flat and the chamfer may be slightly rounded. Chamfering of sizes up to and including No.8 UNC/F or3 BA shall be optional. 2.7.2 Set screws 2.7.2.1 Set screws may be supplied with any type of point sp
40、ecified inTable 6, as required by the purchaser. Unless otherwise specified cup point shall be supplied. 2.7.2.2 The face of the socket ends of the screws shall be chamfered at30 /45 to slightly below the root diameter of the thread except that screws equal to or shorter than those shown in columns5
41、 to7 ofTable6 shall be chamfered at the option of the manufacturer. 2.7.2.3 The chamfer at the point end of the flat and cup point set screws shall be45 /50 , except that screws equal to or shorter than those shown in column5 ofTable 6 shall be chamfered at30 /50 . The point angles specified shall a
42、pply only to those portions of the angles which lie below the root diameter of the thread. 2.8 Screw threads 2.8.1 ISO inch (Unified) threads. UNC and UNF screw threads shall conform to the limits and tolerances for Class2A, or Class3A, as specified in BS1580. 2.8.2 BA screw threads. BA screw thread
43、s shall conform to the limits and tolerances for normal or close class, as specified in BS93. 2.8.3 BSW and BSF screw threads. BSW and BSF screw threads shall conform to the limits and tolerances for medium or close class, as specified in BS84. 2.8.4 G(BSPF) screw threads. G(BSPF) screw threads shal
44、l conform to the limits and tolerances for Class A threads of BSP sizes as specified in BS2779 1) . 2.9 Radius under head 2.9.1 Cap and button head screws. The radius under the heads of the screws shall run smoothly into the face of the head and shank without any step or discontinuity. NOTEA true ra
45、dius is not essential provided that the curve is smooth and lies wholly within the maximum radius determined from the maximum transitional diameter and the minimum radius specified. 2.9.2 Countersunk head screws. The radius under the head of the screws shall run smoothly into the conical bearing sur
46、face of the head and the shank without any step or discontinuity. 2.10 Length of thread 2.10.1 General. The length of thread T shown inTable 2 shall be the distance from the extreme end of the screw, including any chamfer, to the leading face of a ring gauge, without chamfer, which has been screwed
47、as far as possible onto the screw by hand. The thread length does not include the runout threads. The runout threads shall not exceed2 1 / 2pitches. 2.10.2 Cap screws. To accommodate different manufacturing techniques two alternative thread lengths are permitted at the option of the manufacturer. Bo
48、th will give the minimum thread length T specified inTable 2 which is equivalent to twice the nominal diameter plus 1 / 2in. The thread length T shall be controlled by the grip length G. The grip length G is the distance from the underside of the head to the leading face of a ring gauge, without cha
49、mfer, which has been screwed as far as possible onto the screw by hand. The grip length includes the runout threads. The tolerance on grip length shall be+02.5 pitches. 2.10.2.1 Option 1. The following are the requirements for thread lengths and grip lengths given inTable 1. 1) Screws of sizes between the heavy lines inTable 1 shall be threaded to within a distance from the underside of the head equal to the grip length G shown inTable 1. Sizes between the heavy lines inTable 1 for which no grip length is shown shall be t
