1、BRITISH STANDARD BS 7795:1995 Specification for Bolts, screws and studs with a pre-applied micro-encapsulated chemical adhesive feature incorporated into the threadBS7795:1995 This British Standard, having been prepared under the directionof the Engineering SectorBoard, was published underthe author
2、ity of the Standards Board and comes intoeffect on 15June1995 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference GME/9 Draft for comment 94/702252 DC ISBN 0 580 24125 4 Committees responsible for this British Standard The preparation of this British Sta
3、ndard was entrusted 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
4、 Tool Makers Association National Association of Fastener Stockholders Society of Motor Manufacturers and Traders Ltd. Washer Manufacturers Association of Great Britain Amendments issued since publication Amd. No. Date CommentsBS7795:1995 BSI 09-1999 i Contents Page Committees responsible Inside fro
5、nt cover Foreword ii 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Protective coatings 1 5 Pre-applied adhesive element dimensions 1 6 Materials and lubrication 1 7 Mechanical properties and performance 3 Annex A (normative) Torque testing 4 Figure 1 Position of pre-applied adhesive element 2
6、 Figure 2 Diameter of pre-applied adhesive element 2 Table A.1 Prevailing torque 4 Table A.2 Breakaway torque 4 List of references Inside back coverBS7795:1995 ii BSI 09-1999 Foreword This British Standard has been prepared by Technical Committee GME/9. It includes performance properties for pre-app
7、lied adhesive type bolts, screws and studs with micro-encapsulated chemical adhesive features 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 n
8、ot of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 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
9、will be indicated in the amendment table on the inside front cover.BS7795:1995 BSI 09-1999 1 1 Scope This British Standard specifies the coatings, dimensions, materials, lubrication and performance requirements for pre-applied adhesive type bolts, screws and studs with a micro-encapsulated chemical
10、adhesive feature incorporated into the thread, when tested at an ambient room temperature between15 C and30 C. It applies to bolts, screws and studs: a) with ISO metric coarse pitch M6 to M20 threads conforming to BS3643-2:1981; b) with specific strength requirements conforming to either BS6104-3:19
11、81, BS6105:1981 or BS EN20898-1:1992, as appropriate; c) with threads of tolerance class 6g or 4h conforming to BS3643-2:1981; d) for application into a mating component with a thread of tolerance class 6H conforming to BS3643-2:1981; e) for use within the temperature range 50 C to+150 C. The follow
12、ing are not covered in the scope of this standard: 1) capability of providing a pressure or liquid seal; 2) performance at temperatures outside the operating range; 3) performance of bolts, screws and studs for which a lubricated coating is not permissible. 2 Normative references This British Standa
13、rd incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or revisions of, any of these publications apply to t
14、his British Standard only when incorporated in it by updating or revision. 3 Definitions For the purposes of this British Standard, the following definitions apply. 3.1 pre-applied adhesive type bolts, screws and studs bolts, screws and studs which are frictionally resistant to rotation due to an in
15、tegral chemical adhesive feature and not because of compressive load developed against a bearing face 3.2 prevailing torque developed by bolts, screws or studs torque necessary to rotate the bolt, screw or stud in a mating threaded component while in motion and with no axial load 3.3 breakaway torqu
16、e developed by pre-applied adhesive type bolts, screws and studs torque necessary to initiate rotation of a bolt, screw or stud that has been assembled into a mating threaded component and then cured with no axial load present 4 Protective coatings Finished parts shall conform to the appropriate coa
17、ting standard applicable to the fastener to which the pre-applied micro-encapsulated chemical adhesive feature is applied. NOTE 1Pre-applied adhesive type bolts, screws or studs which do not have or need supplementary lubrication may not satisfy the requirements of this standard unless the lubricati
18、on is an integral property of the specified coating. NOTE 2Additional protection for storage may be applied either before or after the application of the chemical adhesive feature at the discretion of the supplier. 5 Pre-applied adhesive element dimensions The pre-applied adhesive feature dimensions
19、 shall be as shown inFigure 1 andFigure 2. Dimension l xshall be selected so that a minimum of two pitches of the screw thread measured from the end of the bolt, screw or stud are free from the pre-applied adhesive feature in order to ensure ease of engagement. 6 Materials and lubrication 6.1 Materi
20、als The materials used to produce the bolts, screws and studs with pre-applied micro-encapsulated chemical adhesive features shall conform to the specified property class in BS6104-3:1981, BS6105:1981 or BS EN20898-1:1992, as appropriate. 6.2 Lubrication NOTEBolts, screws or studs finished in accord
21、ance with BS7371-1:1991 and requiring no lubrication may be lubricated at the discretion of the supplier. Bolts, screws or studs finished in accordance with BS7371-1:1991 with a finish which requires lubrication shall be lubricated. Supplementary lubrication, if applied, shall conform to BS7371-2:19
22、93.BS7795:1995 2 BSI 09-1999 l is the length of bolt; l x is the distance from under head to centre of locking feature; p is the pitch of thread. Figure 1 Position of pre-applied adhesive element d 1 d has specified for fine series threads in BS EN20273:1992 Figure 2 Diameter of pre-applied adhesive
23、 elementBS7795:1995 BSI 09-1999 3 7 Mechanical properties and performance 7.1 Mechanical properties The mechanical properties of the bolt, screw or stud after application of the pre-applied micro-encapsulated chemical adhesive shall conform to the specified property class in BS6104-3:1981, BS6105:19
24、81 or BS EN20898-1:1992, as appropriate. 7.2 Prevailing torque on assembly The prevailing torque developed by the chemical adhesive feature during the first assembly shall not exceed the maximum prevailing torque specified inTable A.1 when tested as specified inAnnex A. 7.3 Breakaway torque of assem
25、bly The breakaway torque developed by the chemical adhesive feature shall be in accordance with the values of breakaway torque specified inTable A.2 when tested as specified inAnnex A. 7.4 Prevailing torque on disassembly Immediately after the measurement of the breakaway torque the prevailing torqu
26、e on disassembly shall be not less than the minimum prevailing torque specified inTable A.1 when tested as specified inAnnex A.BS7795:1995 4 BSI 09-1999 Annex A (normative) Torque testing A.1 Torque measuring device The torque measuring device (torque wrench or power device) shall be accurate to2% o
27、f the maximum specified torque range of the device. For referee purposes, the device shall be chosen so that all readings fall within the upper half of the torque range. Manual torque wrenches may be used for measurement of torque, but for referee purposes, an automatic electronic sensing device sha
28、ll be used. A.2 Test nuts The test nuts shall be steel of product grade B, unplated and clean in accordance with BSEN24032:1992. A new nut shall be used for eachtest. A.3 Test procedure Conduct the prevailing torque test at ambient temperature between15 C and30 C. Measure all prevailing torque measu
29、rements by a torque measuring device (seeA.1) with the bolt, screw or stud in motion. Assemble the sample bolt, screw or stud into a test nut described inA.2. Advance the bolt, screw or stud into the test nut until all the test nut threads are in contact with the adhesive coated threads of the bolt,
30、 screw or stud. Measure the maximum torque occurring while the bolt, screw or stud is being advanced into the test nut. For the bolt, screw or stud to be acceptable, check that this torque does not exceed the maximum prevailing torque value as specified for the applicable thread size inTable A.1. En
31、sure that no clamp load is induced into the bolt, screw or stud. Allow the resultant assembly to cure for24h at20 C. After the assembly has been allowed to cure, measure the breakaway torque of the bolt, screw or stud. For the bolt, screw or stud to be acceptable, check that this torque is within th
32、e minimum/maximum breakaway torque values as specified for the applicable thread size inTable A.2. Disassemble the bolt, screw or stud from the test nut. Measure the minimum torque occurring while the bolt screw or stud is being unscrewed. For the bolt, screw or stud to be acceptable, check that thi
33、s torque exceeds the minimum prevailing torque value as specified for the applicable thread size inTable A.1. Table A.1 Prevailing torque Table A.2 Breakaway torque Torque dimensions are in newton metres Thread size Assembly prevailing torque Disassembly prevailing torque Maximum Minimum M6 1 1.8 0.
34、8 M8 1.25 2.8 2.0 M10 1.5 5.5 4.0 M12 1.75 7.2 7.0 M14 2 11.0 10.0 M16 2 14.0 16.0 M20 2 22.0 22.0 Torque dimensions are in newton metres Thread size Breakawaytorque Maximum Minimum M6 1 8 2 M8 1.25 24 4 M10 1.5 44 10 M12 1.75 80 15 M14 2 130 20 M16 2 160 30 M20 2 240 45BS7795:1995 BSI 09-1999 List
35、of references (seeclause2) Normative references BSI publications BRITISH STANDARDS INSTITUTION, London BS 3643, ISO metric screw threads. BS 3643-2:1981, Specification for selected limits of size. BS 6104, Mechanical properties of fasteners. BS 6104-3:1981, Specification for set screws and similar t
36、hreaded fasteners not under tensile stresses. BS 6105:1981, Specification for corrosion-resistant stainless steel fasteners. BS 7371, Coatings on metal fasteners. BS 7371-1:1991, Specification for general requirements and selection guidelines. BS 7371-2:1993, Specification for torque/clamping force
37、relationship. BS EN 20273:1992, Fasteners. Clearance holes for bolts and screws. BS EN 20898, Mechanical properties of fasteners. BS EN 20898-1:1992, Bolts, screws and studs. BS EN 24032:1992, Hexagon nuts, style 1 Product grades A and B. BS 7795:1995 BSI 389 Chiswick High Road London W4 4AL BSIBrit
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