1、BRITISH STANDARD BS 7814:1995 Specification for Bolts and screws incorporating either underhead locking or anti-rotation features UDC 681.3:621.39BS7814:1995 This British Standard, having been prepared under the directionof the Engineering SectorBoard, was published underthe authority of the Standar
2、ds Board and comes intoeffect on 15 December 1995 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference GME/9 Draft for comment 94/704978 DC ISBN 0 580 24520 9 Committees responsible for this British Standard The preparation of this British Standard was en
3、trusted to Technical Committee GME/9, Bolts, nuts and accessories, upon which the following bodies were represented: BEAMA Ltd. British Constructional Steelwork Association Ltd. British Industrial Fasteners Federation British Steel Industry British Steel Industry (Wire Section) Gauge and Tool Makers
4、 Association National Association of Fastener Stockholders Society of Motor Manufacturers and Traders Ltd. Washer Manufacturers Association of Great Britain The following bodies were also represented in the drafting of the standard, through subcommittees and panels: British Turned-parts Manufacturer
5、s Association Institute of Metal Finishing Metal Finishing Association National Centre of Tribology Stainless Steel Fabricators Association of Great Britain Amendments issued since publication Amd. No. Date CommentsBS7814:1995 BSI 08-1999 i Contents Page Committees responsible Inside front cover For
6、eword ii 1 Scope 1 2 Normative reference 1 3 Information and requirements to be agreed and to be documented 1 4 Materials 1 5 Mechanical properties 1 6 Test methods 2 7 Marking 2 Figure 1 Examples of marking on hexagon bolts and screws 3 Figure 2 Examples of marking on hexagon socket head 3 Figure 3
7、 Left-hand thread marking 3 Table 1 Equivalent property class of fastener from BS EN 20898-1:1992 for material selection 1 Table 2 Additional mechanical properties for bolts and screws with underhead locking or anti-rotation features 1 Table 3 Surface hardness for bolts and screws with locking or an
8、ti-rotation features 2 Table 4 Marking symbols 2 List of references Inside back coverBS7814:1995 ii BSI 08-1999 Foreword This British Standard has been prepared by Technical Committee GME/9. It includes mechanical properties for bolts and screws with either underhead locking or anti-rotation feature
9、s. A British Standard does not purport to include all the 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 compris
10、es a front cover, an inside front cover, pages i and ii, pages1 to 4, an inside back cover 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.BS7814:1995 BSI 08-1999 1
11、 1 Scope This British Standard specifies the materials, mechanical properties and marking requirements for bolts and screws incorporating either underhead locking or anti-rotation features when tested at an ambient temperature between15 C and30 C. It applies to bolts and screws: a) with ISO metric M
12、2 to M20 threads conforming to BS3643-2:1981; b) with mechanical properties80,90or100 1)as appropriate; c) for use within the temperature range 50 C to+250 C. As the decarburization of any underhead locking or anti-rotation feature will seriously impair its intended function, partial or complete dec
13、arburization as given in BSEN20898-1:1992does not apply to this standard. There is instead a requirement for carbon restoration to ensure that no decarburization of the locking or anti-rotation feature takes place during the heat treatment process. NOTEPerformance at temperatures outside the operati
14、ng range is not within the requirements of this standard. 2 Normative reference This British Standard incorporates by dated or undated reference provisions from other publications. These normative references are made at the appropriate places in the text and the cited publications are listed on the
15、inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revisions of the cited publication apply to this standard only when incorporated in the reference by amendment or revision. For undated reference, the latest edition of the cited publication appl
16、ies, together with any amendments. 3 Information and requirements to be agreed and to be documented The following items to be agreed between the contracting parties, which are specified in the clauses referred to, shall be fully documented. Both the definitive requirements specified throughout the s
17、tandard and the following documented items shall be satisfied before a claim of compliance with a standard can be made and verified. a) if an anti-rotation feature is required the hole diameter in the component into which the knurl bolt is assembled shall be agreed at the time of enquiry and/or orde
18、r (see5.5). b) if a particular surface treatment applied to bolts and screws with underhead locking or anti-rotation features is required it shall be agreed at the time of enquiry and/or order (see5.6). 4 Materials The steels used to produce bolts and screws with underhead locking or anti-rotation f
19、eatures shall be in accordance with those specified in Table2of BSEN20898-1:1992 for the equivalent property class of fastener as stipulated in Table 1. Table 1 Equivalent property class of fastener from BS EN 20898-1:1992 for material selection 5 Mechanical properties 5.1 General The mechanical pro
20、perties of bolts and screws with underhead locking or anti-rotation features shall be in accordance with the following: Table 2; ISO 898-7:1992; clause 5 of BS EN 20898-1:1992, with the exception of 5.6 and 5.11, for the equivalent property classes stipulated in Table 1. Table 2 Additional mechanica
21、l properties for bolts and screws with underhead locking or anti-rotation features 1) With the exception of surface hardness and strength under wedge loading the mechanical properties80,90and100are in line with the respective mechanical properties of property classes8.8,9.8and10.9of BS EN 20898-1:19
22、92 Mechanical property class Equivalent property class of fastener from BS EN 20898-1:1992 80 8.8 90 9.8 100 10.9 or 10.9 Mechanical property Clause Test method Wedge tensile strength 5.2 See 8.4 of BS EN 20898-1:1992 Decarburization and carbon restoration 5.3 6.1 Surface hardness 5.4 6.2 Anti-rotat
23、ion feature 5.5 Surface treatment and embrittlement 5.6 BS7814:1995 2 BSI 08-1999 5.2 Wedge tensile strength Bolts and screws with underhead locking or anti-rotation features shall be heat treated to achieve the minimum tensile strength specified in Table3 of BSEN20898-1:1992, for the equivalent pro
24、perty class as stipulated inTable 1, when tested against a6 wedge. 5.3 Decarburization and carbon restoration In order to eliminate any decarburization during heat treatment, the carbon potential of the atmosphere inside the furnace where the heat treatment takes place shall be maintained at a level
25、 slightly in excess of the carbon content of the steel from which the bolt or screw has been manufactured. There shall be no decarburization. Carbon enrichment of the surface of a bolt or screw up to a depth of0.1mm maximum for the size range M2 to M12 inclusive and0.25mm maximum for the size range
26、M14 to M20 inclusive shall be allowed as the result of the carbon restoration process. NOTEThe decarburization specified in BSEN20898-1:1992 is not applicable to this standard as it would impair the performance of any underhead locking or anti-rotation feature. 5.4 Surface hardness The minimum tempe
27、ring temperature specified in BS EN20898-1:1992 for the equivalent property classes stipulated in Table 1 shall apply to bolts and screws in this standard. When tested in accordance with6.2 the surface hardness of bolts and screws with underhead locking or anti-rotation features shall be as given in
28、Table 3. Table 3 Surface hardness for bolts and screws with locking or anti-rotation features 5.5 Anti-rotation feature Bolts with an anti-rotation feature, commonly known as knurl bolts, shall without permanent deformation of the anti-rotation feature when viewed at10times magnification, produce a
29、mating form in the component to which they are assembled. The hole diameter in the component into which the knurl bolt is assembled shall be agreed between the customer and supplier in order to take account of such variations as material hardness and length of engagement see3 a). 5.6 Surface treatme
30、nt and embrittlement The surface treatment applied to bolts and screws with underhead locking or anti-rotation features shall be agreed between the customer and supplier see3 b). NOTEAs fasteners to this standard are susceptible to embrittlement non-electrolytic coatings should be the preferred opti
31、on. 6 Test methods 6.1 Decarburization test Longitudinal sections shall be taken through the axis at a distance of approximately one times the nominal thread diameter from the end of the bolt or screw. The sections shall be suitably mounted and prepared for metallographic examination at not less tha
32、n100times magnification. Prior to the metallographic examination the prepared specimen shall be etched in2% nital solution. 6.2 Surface hardness test The surface hardness shall be measured using the Vickers hardness testing procedure specified in ISO6507-1:1982. The surface hardness shall be measure
33、d on the head or end of the bolt or screw after the removal of any surface treatment and any suitable preparation of the specimen. NOTECare should be taken to remove as little material as possible during the preparation of the specimen. For referee purposes a micro-hardness instrument with a Vickers
34、 indenter and a300g load shall be used. In such cases, measurements shall be made on the thread profile of a suitably prepared longitudinal metallographic specimen. 7 Marking 7.1 Symbols Marking symbols are shown inTable 4. Table 4 Marking symbols 7.2 Identification Bolts and screws with underhead l
35、ocking or anti-rotation features and with nominal thread diameters of5mm or greater shall be marked with the appropriate marking symbol for the mechanical property class of the fastener. The markings shall be by indenting or embossing on the top of the head or indenting on the side of the head, seeF
36、igure 1 andFigure 2. Mechanical property class surface hardness (Hv5) 80 270 to 370 90 300 to 390 100 340 to 430 Mechanical property class 80 90 100 Marking symbol 80 90 100BS7814:1995 BSI 08-1999 3 7.3 Marking of left-hand threads Bolts and screws with underhead locking or anti-rotation features wi
37、th nominal thread diameter of5mm or greater and left hand thread shall be marked with the symbol shown inFigure 3, either on the top of the head or the point. 7.4 Trade (identification) marking The trade (identification) marking of the manufacturer shall be marked on all products which are required
38、to be marked with the mechanical property class marking symbol. Figure 1 Examples of marking on hexagon bolts and screws Figure 2 Examples of marking on hexagon socket head cap screws Figure 3 Left-hand thread marking4 blankBS7814:1995 BSI 08-1999 List of references (see clause 2) Normative referenc
39、es BSI publication BRITISH STANDARDS INSTITUTION, London BS 3643, ISO metric screw threads. BS 3643-2:1981, Specification for selected limits of size. BS EN 20898, Mechanical properties of fasteners. BS EN 20898-1:1992, Bolts, screws and studs. ISO publications International Organization for Standar
40、dization (ISO), Geneva. All publications are available from BSI Customer Services. ISO 898, Mechanical properties of fasteners. ISO 898-7:1992, Torsional test and minimum torques for bolts and screws with nominal diameters1mm to10mm. ISO 6507, Metallic materials Hardness test Vickers test. ISO 6507-
41、1:1982, HV 5 to HV 100. BS 7814:1995 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Cha
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