1、BRITISH STANDARD BS 4174:1972 Incorporating Amendment No. 1 Specification for Self-tapping screws and metallic drive screws UDC 621.882.082.8BS4174:1972 This British Standard, having been approved by the MechanicalIndustry StandardsCommittee, was published under the authorityofthe Executive Boardon
2、25September1972 BSI 01-2000 First published 31May1967 First revision September1972 The following BSI references relate to the work on this standard; Committee references MEE/60, MEE/60/9 Draft for comment70/31170 ISBN 0580 07337 8 Co-operating organizations The Mechanical Engineering Industry Standa
3、rds Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Associated Offices Technical Committee. Engineering Equipment Users Association* Association of Consulting Eng
4、ineers Gas Council Association of Mining Electrical and Institution of Civil Engineers Mechanical Engineers Institution of Gas Engineers British Chemical Plant Manufacturers Institution of Heating and Ventilating Engineers Association Institution of Mechanical Engineers British Compressed Air Societ
5、y Institution of Mechanical Engineers British Electrical and Allied Manufacturers (Automobile Division) Association* Institution of Plant Engineers British Gear Manufacturers Association Institution of Production Engineers British Internal Combustion Engine London Transport Executive Manufacturers A
6、ssociation Machine Tool Trades Association British Steel Industry* Ministry of Defence British Mechanical Engineering Federation Ministry of Defence, Army Department Crown Agents for Oversea Governments and National Coal Board* Administrations Railway Industry Department of the Environment Royal Ins
7、titute of British Architects Department of Employment and Productivity Telecommunication Engineering and Department of Trade and Industry Manufacturing Association Electricity Council, the Central Electricity Water-tube Boilermakers Association Generating Board and the Area Boards in England and Wal
8、es* The scientific and industrial 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: Association of Hydraulic Equipment Institute of Iron and Steel Wire Manufacturer
9、s Manufacturers Ministry of Defence, Navy Department British Bolt, Nut, Screw and Rivet Federation Post Office British Constructional Steelwork Association Precision Bolt and Nut Institute British Railways Board Rolled Thread Screw Association Council of British Manufacturers of Scientific Instrumen
10、t Manufacturers Petroleum Equipment Association Electronic Engineering Association Society of Motor Manufacturers and Traders Fasteners and Turned Parts Institute Ltd. Individual manufacturers Amendments issued since publication Amd. No. Date of issue Comments 8549 May 1995 Indicated by a sideline i
11、n the marginBS4174:1972 BSI 01-2000 i Contents Page Co-operating organizations Inside front cover Foreword iii 1 Scope 1 2 Styles of head 1 3 Types of screws and type designations 1 4 Material and manufacture 3 5 Finish 3 6 Dimensions 3 7 Heads of screws 3 8 Length of screws 4 9 Screw threads 5 10 L
12、ength of thread 5 11 Diameter of unthreaded shank 6 12 Radius under head 6 13 Testing 6 14 Designation for ordering 6 Appendix A Thread and point details for Type A threads 26 Appendix B Dimensioning of countersunk and raised countersunk head screws 27 Appendix C Recess penetration gauging 28 Append
13、ix D Testing 31 Appendix E Recommended hole sizes 32 Appendix F Preferred lengths of self-tapping screws 42 Appendix G Slot widths 45 Figure 1 Countersunk head 27 Figure 2 Countersunk head gauge 27 Figure 3 Recess penetration gauge 28 Figure 4 Typical gauge point enlarged 29 Table 1 Types of screws
14、and type designations for tapping screws and metallic drive screws 2 Table 2 Type AB, A, B, BD, D, T and Y thread forming and cutting screws 4 Table 3 Metallic drive screws, Type U 4 Table 4 Short screws 5 Table 5 Type AB and B thread forming screws and Type BT thread cutting screws 7 Table 6 Type Y
15、 thread cutting screws 8 Table 7 Types D and T thread cutting screws (unified form threads) 9 Table 8 80 countersunk head screws 10 Table 9 Recess dimensions for 80 countersunk head screws 11 Table 10 80 truncated countersunk head screws 12 Table 11 Recess dimensions for 80 truncated countersunk hea
16、d screws 13 Table 12 80 raised countersunk head screws 14 Table 13 Recess dimensions for 80 raised countersunk head screws 15 Table 14 80 truncated raised countersunk head screws 16 Table 15 Recess dimensions for 80 truncated raised countersunk head screws 17 Table 16 Pan head screws 18BS4174:1972 i
17、i BSI 01-2000 Page Table 17 Recess dimensions for pan head screws 20 Table 18 Mushroom head screws 21 Table 19 Recessed flange head screws 22 Table 20 Recess dimensions for flange head screws 23 Table 21 Hexagon head screws 24 Table 22 Round head Type U metallic drive screws 25 Table 23 Thread and p
18、oint details for Type A thread forming screws 26 Table 24 Dimensions of gauge point 30 Table 25 Torque test, thread cutting screws 31 Table 26 Torque test, thread cutting screws (unified form threads) 31 Table 27 Application test, test plates for thread forming and thread cutting screws 31 Table 28
19、Application test, test plates for types D and T thread cutting screws (unified form threads) 32 Table 29 Types AB and B self tapping screws in sheet metal 33 Table 30 Type B self-tapping screws in non-ferrous castings 34 Table 31 Type B hexagon head self-tapping screws in structural steel 34 Table 3
20、2 Type U hammer drive screws 35 Table 33 Types D and T thread cutting screws in sheet steel 36 Table 34 Types D and T thread cutting screws in sheet aluminium and brass 37 Table 35 Types D and T thread cutting screws in non-ferrous castings 38 Table 36 Type T and BT thread cutting screws in plastics
21、 39 Table 37 Type BT thread cutting screws in non-ferrous castings 40 Table 38 Type BT thread cutting screws in sheet steel 41 Table 39 Type AB self-tapping screws 42 Table 40 Type U round head hammer drive screws 43 Table 41 Type Y self-tapping screws 43 Table 42 Type B self-tapping screws 44 Table
22、 43 Types BT, D and T self-tapping screws 44 Table 44 Type A self-tapping screws 45 Table 45 New metric slot widths 45BS4174:1972 BSI 01-2000 iii Foreword This standard makes reference to the following British Standards: BS 1580, Unified screw threads. BS 4500, ISO limits and fits. BS 4183, Machine
23、screws and machine screw nuts. Metric series. This revised British Standard has been prepared under the authority of the Mechanical Engineering Industry Standards Committee to supersede the first edition published in1967. Since1967 the International Committee on Bolts, Nuts and Accessories (ISO/TC2)
24、, has prepared ISO Draft Recommendations Nos.14781483 for Type AB and Type B self tapping screws based on the American Standard USASB18,6.4. This revision of BS4174 introduces Type AB self tapping screws which are recommended instead of Type A. Type A has been declared obsolescent, but information o
25、n this type has been retained as an Appendix to this standard until such time as it becomes obsolete. In addition metric equivalents of the inch dimensions have been included together with details of metric hexagon heads for Types AB, B, BT and Y. A British Standard does not purport to include all t
26、he 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, pages i to iv,
27、 pages1to45 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.iv blankBS4174:1972 BSI 01-2000 1 Obsolescent (by Amendment No.1). The need for screws covered by this B
28、ritish Standard has been reviewed and it has been decided that in the interests of rationalization they should be regarded as obsolescent. Their use for new designs is not therefore recommended. The standard will be withdrawn in due course. Even though this standard has largely been superseded by a
29、series of BS EN standards of which BS EN ISO1479:1994 and BS EN ISO7049:1994 are typical examples, it has not been withdrawn but declared obsolescent as it is recognized that it should remain available for the servicing of existing designs which are expected to have a long working life. 1 Scope This
30、 British Standard relates to ferrous and non-ferrous tapping screws and metallic drive screws. Provisions are made for two classes of tapping screw, namely thread forming and thread cutting, each available in several types which are described and illustrated in the standard. General dimensions are g
31、iven for countersunk, raised countersunk, and pan head tapping screws with slotted or recessed heads, slotted mushroom heads, recessed flange heads and hexagon head tapping screws and round head metallic drive screws. Countersunk and raised countersunk head tapping screws in short lengths have shall
32、ower truncated heads than those in normal lengths and separate tables of dimensions are accordingly provided. Details of a suitable head flushness gauge for countersunk head screws and a gauge for checking recess penetration on recessed head screws together with testing requirements for the inspecti
33、on of tapping screws and approximate hole sizes for steel screws in various materials, are given with appendices. NOTE 1Round head screws other than metallic drive screws have not been included in this standard as it is considered that pan head screws provide for most of the applications in which ro
34、und head screws are normally used and allow more conveniently for the application of torque. NOTE 2The titles of the British Standards referred to in this standard are given on pageiii. 2 Styles of head 2.1 The descriptions of the various types of screw head are in accordance with those commonly use
35、d in British practice. The equivalent British and American terms are listed for information below: 2.2 American “type designations” are used to indicate the type of tapping or drive screw and these are shown, together with their former (British) equivalents, inTable 1. 3 Types of screws and type des
36、ignations 3.1 General. The various types of thread forming, thread cutting and drive screw covered by this standard are as shown inTable 1. 3.2 Thread forming screws. These screws are for application in materials which allow sufficient plastic deformation to enable the thread to be formed by displac
37、ement without the removal of any material. 3.2.1 Type AB. These screws have widely spaced threads and gimlet points. The thread pitches are the same as those of Type B. They are primarily intended for use in light sheet metal, metal-clad and resin-impregnated plywood, soft plastics, etc. Type AB is
38、suitable for applications in which Type A has previously been used. British American Hexagon Countersunk Truncated countersunk Raised countersunk Truncated raised countersunk Pan Mushroom Flange Round-head (metallic drive screws only) Hexagon Flat Undercut flat Oval Undercut oval Pan Truss Flange Ro
39、und-head (metallic drive screws only)BS4174:1972 2 BSI 01-2000 3.2.2 Type B. These screws have widely spaced threads and blunt, slightly tapered points. These screws are primarily intended for use in light and heavy sheet metal, non-ferrous castings, soft plastics, metal-clad and resin-impregnated p
40、lywood, etc. 3.2.3 Type A. These screws have widely spaced threads and gimlet points. The pitch is coarser than for Types AB and B. They are primarily intended for use in light sheet metal, metal-clad and resin-impregnated plywood, soft plastics, etc. This type of screw is now obsolescent and it is
41、recommended that Type AB be substituted where Type A screws are now specified. Table 1 Types of screws and type designations for tapping screws and metallic drive screws 3.3 Thread cutting screws. These screws are for applications in materials which do not allow plastic deformation to an extent suff
42、icient to form a thread by displacement. They may also be used, however, inmaterials which do allow plastic deformation and may have the advantage of a lower driving torque than thread forming screws. In some cases they may have the further advantage of a standard machine screw thread form. Details
43、of these types and their application are as follows: 1) Type BT. These screws are similar to the Type B thread forming screws but have one cutting flute extending for a short distance from the point of the screw. They are primarily intended for use in light and heavy sheet metal, non-ferrous casting
44、s, plastics, die castings, metal-clad and resin-impregnated plywood, asbestos and other compositions. 2) Type Y. These screws have widely spaced threads, blunt, slightly tapered points and cutting flutes which extend from the point to the head. They are similar to the American Type BF except that th
45、e cutting flutes on the American screws extend only a short distance from the point of the screw. These screws are primarily intended for use in plastics, die castings, metal-clad and resin-impregnated plywood, asbestos and other compositions. 3) Type D. These screws have threads of unified form clo
46、sely approximating to machine screw threads. They have blunt, slightly tapered points and one slot to form a cutting edge extending for a short distance from the point of the screw. They are suitable for use in such materials as aluminium, zinc, and lead die castings, steel sheets and shapes, cast i
47、ron, brass, plastics, etc. Thread contour Type of screw Type designation for tapping screws and metallic drive screws Thread forming AB Thread forming B (formerly Z) Thread cutting T (formerly 23) Thread cutting Y Thread cutting D (formerly 1) Thread cutting BT (formerly 25) Drive U Thread forming A
48、 Not recommended; use Type ABBS4174:1972 BSI 01-2000 3 4) Type T. These screws have threads of unified form closely approximating to machine screw threads. They have blunt, slightly tapered points and one or more cutting flutes extending for a short distance from the point of the screw. These screws
49、 are suitable for use in materials such as aluminium, zinc and lead die castings, steel sheets and shapes, cast iron, brass, plastics, etc. 3.4 Metallic drive screws. These screws are designated Type U. They have multiple threads with a large lead angle and a pilot point. Primarily for use in cast iron, metal shapes and plastics, these screws are hammered or forced into the appropriate holes and are intended for making permanent fastenings. 4 Material and Manufactu
