1、BS ISO 8641:2008 ICS 49.030.30 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BRITISH STANDARD Aerospace Self- locking nuts with maximum operating temperature greater than 425 degrees C Procurement specificationThis British Standard was published under the authority of the St
2、andards Policy and Strategy Committee on 30 September 2008 BSI 2008 ISBN 978 0 580 55583 1 Amendments/corrigenda issued since publication Date Comments BS ISO 8641:2008 National foreword This British Standard is the UK implementation of ISO 8641:2008. The UK participation in its preparation was entr
3、usted to Technical Committee ACE/12, Aerospace fasteners and fastening systems. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its co
4、rrect application. Compliance with a British Standard cannot confer immunity from legal obligations.BS ISO 8641:2008Reference number ISO 8641:2008(E) ISO 2008INTERNATIONAL STANDARD ISO 8641 Second edition 2008-09-01 Aerospace Self-locking nuts with maximum operating temperature greater than 425 C Pr
5、ocurement specification Aronautique et espace crous freinage interne dont la temprature maximale dutilisation est suprieure 425 C Spcification dapprovisionnement BS ISO 8641:2008 ISO 8641:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy,
6、 this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobes licensing policy. The ISO Central Sec
7、retariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to e
8、nsure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2008 All rights reserved. Unless otherwise specified, no part of this publica
9、tion may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva
10、20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedBS ISO 8641:2008 ISO 8641:2008(E) ISO 2008 All rights reserved iii Contents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Terms and definitions.
11、 2 4 Quality assurance. 4 4.1 General. 4 4.2 Qualification inspection and test conditions. 4 4.3 Production acceptance inspection and test conditions. 4 4.4 Use of “statistical process control (SPC)”. 5 5 Technical requirements . 5 Annex A (normative) Type of permissible surface discontinuities (see
12、 5.1.3) 21 Annex B (informative) Cross-sectional area and formulae for axial loads (see Table 3) 22 BS ISO 8641:2008 ISO 8641:2008(E) iv ISO 2008 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bo
13、dies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental an
14、d non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives,
15、 Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies cas
16、ting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 8641 was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Sub
17、committee SC 4, Aerospace fastener systems. This second edition cancels and replaces the first edition (ISO 8641:1987) which has been technically revised. BS ISO 8641:2008 INTERNATIONAL STANDARD ISO 8641:2008(E) ISO 2008 All rights reserved 1 Aerospace Self-locking nuts with maximum operating temper
18、ature greater than 425 C Procurement specification 1 Scope This International Standard specifies the required characteristics for metric self-locking nuts, with MJ thread, for use in aerospace construction at a maximum temperature greater than 425 C. It is applicable to nuts as defined above, provid
19、ed that reference is made to this International Standard in the relevant definition document. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edi
20、tion of the referenced document (including any amendments) applies. ISO 691, Assembly tools for screws and nuts Wrench and socket openings Tolerances for general use ISO 1463, Metallic and oxide coatings Measurement of coating thickness Microscopical method ISO 2859-1:1999, Sampling procedures for i
21、nspection by attributes Part 1: Sampling schemes indexed by acceptable quality level (AQL) for lot-by-lot inspection ISO 4288, Geometrical Product Specifications (GPS) Surface texture: Profile method Rules and procedures for the assessment of surface texture ISO 5855-2, Aerospace MJ threads Part 2:
22、Limit dimensions for bolts and nuts ISO 7403, Aerospace Spline drives Wrenching configuration Metric series ISO 7870-1, Control charts General guidelines ISO 7966, Acceptance control charts ISO 8258, Shewhart control charts ISO 8642, Aerospace Self-locking nuts with maximum operating temperature gre
23、ater than 425 C Test methods ISO 8788, Aerospace Nuts, metric Tolerances of form and position ISO 9199, Aerospace Nuts, bihexagonal, self-locking, MJ threads, classifications: 1 100 MPa (at ambient temperature)/425 C, 1 100 MPa (at ambient temperature)/650 C, 1 210 MPa (at ambient temperature)/425 C
24、, 1 210 MPa (at ambient temperature)/730 C, 1 550 MPa (at ambient temperature)/235 C, 1 550 MPa (at ambient temperature)/425 C and 1 550 MPa (at ambient temperature)/600 C Dimensions ISO/TR 13425, Guidelines for the selection of statistical methods in standardization and specification BS ISO 8641:20
25、08 ISO 8641:2008(E) 2 ISO 2008 All rights reserved3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 definition document document specifying all the requirements for nuts, i.e.: metallurgical; geometrical and dimensional; functional (strength an
26、d temperature classes) NOTE The definition document can be an International Standard, a national standard, an in-house standard or a drawing. 3.2 finished nut nut ready for use, inclusive of any possible treatments and/or surface coatings, as specified in the definition document 3.3 batch definite q
27、uantity of some commodity manufactured or produced under conditions which are presumed to be uniform NOTE For the purposes of this International Standard, a batch is a quantity of finished nuts, of the same type and same diameter, produced from a material obtained from the same melt, manufactured in
28、 the course of the same production cycle, following the same manufacturing route and having undergone all the relevant heat treatments and surface treatments. 3.4 crack rupture in the material which may extend in any direction and which may be intercrystalline or transcrystalline in character 3.5 se
29、am open surface defect resulting from extension of the metal 3.6 lap folding over of unwelded metal that can arise when the material is formed (drawing) or in the finished product (pressing or forging) 3.7 inclusions non-metallic particles originating from the material manufacturing process NOTE The
30、se particles can be isolated or arranged in strings. 3.8 critical defect defect that, according to judgement and experience, is likely to result in hazardous or unsafe conditions for individuals using, maintaining or depending upon the considered product, or that is likely to prevent performance of
31、the function of a major end item BS ISO 8641:2008 ISO 8641:2008(E) ISO 2008 All rights reserved 3 3.9 major defect defect other than critical, that is likely to result in a failure or to reduce materially the usability of the considered product for its intended purpose 3.10 minor defect defect that
32、is not likely to reduce materially the usability of the considered product for its intended purpose, or that is a departure from established specifications having little bearing on the effective use or operation of this product 3.11 sampling plan plan according to which one or more samples are taken
33、 in order to obtain information and possibly reach a decision NOTE For the purposes of this International Standard, each sampling plan specifies the number of nuts to be inspected as a function of the size of the batch and the acceptance number number of defective items acceptable (Ac) 1) . 3.12 sim
34、ple random sampling sampling of n items from a population of N items in such a way that all possible combinations of n items have the same probability of being chosen 3.13 acceptance quality limit AQL maximum percent defective (or the maximum number of defects per hundred units) that, for purposes o
35、f sampling inspection, can be considered satisfactory as a process average NOTE Variant: quality limit which in a sampling plan corresponds to a specified but relatively high probability of acceptance. 3.14 limiting quality LQ sampling plan quality level that corresponds to a specified and relativel
36、y low probability of acceptance NOTE 1 It is the limiting lot quality characteristic that the consumer is willing to accept with a low probability that a lot of this quality would occur. NOTE 2 For the purposes of this International Standard, the limiting quality given in Table 11 corresponds to a c
37、onsumers risk of 10 %. 3.15 self-locking torque torque to be applied to the nut or bolt to maintain its movement of rotation in relation to the associated part, the assembly being under no axial load and the nut-locking system being completely engaged with the bolt (two pitches minimum protrusion in
38、cluding the end chamfer) 3.16 seating torque tightening torque to be applied to the nut or bolt to introduce or to increase the axial load in the assembly 3.17 unseating torque untightening torque to be applied to the nut or bolt to reduce or remove the axial load in the assembly 1) Ac = acceptance
39、number (supplementary information taken from ISO 2859-1). BS ISO 8641:2008 ISO 8641:2008(E) 4 ISO 2008 All rights reserved3.18 breakaway torque torque required to start unscrewing the nut or bolt with respect to the associated part, with the nut-locking device still fully engaged on the bolt, but af
40、ter the axial load in the assembly has been removed by unscrewing half a turn followed by a half in rotational movement 3.19 wrench torque tightening and untightening torques which the driving feature of the nut shall withstand repeatedly, without any permanent deformation which would prevent the ap
41、propriate wrench from being used and preclude re-use of the nut 4 Quality assurance 4.1 General The manufacturer shall be capable of continuous production of bolts complying with the quality requirements specified in this International Standard. It is recommended that the manufacturer be certified t
42、o a recognized quality management system. The certification authority may be the prime contractor. The purpose of qualification inspections of nuts is to check that the design and manufacturing conditions of a bolt allow it to satisfy the requirements of this International Standard. Qualification of
43、 the bolts shall be granted by the Certification Authorities in the purchasers country, or their appointed representative, who may be the prime contractor. The purpose of production acceptance inspection of a nut is to check, as simply as possible, using a method which is inexpensive but the most re
44、presentative of the actual conditions of use, with the uncertainty inherent in statistical sampling, that the bolts satisfy the requirements of this International Standard. Production acceptance inspections and tests shall be carried out by the manufacturer, or under his responsibility. 4.2 Qualific
45、ation inspection and test conditions Qualification inspections and tests (requirements, methods, numbers of nuts) are specified in Table 1. They shall be carried out on: each type and diameter of nut; 100 nuts selected from a single batch by simple random sampling. The test programme may possibly be
46、 reduced, or qualification of a nut granted, without inspection or testing; any such decision shall be based on the results obtained on similar types and diameters of nuts provided that the design and manufacturing conditions are identical. The inspections and tests shall be repeated on any nut if t
47、he supplier or the manufacturing conditions have changed. Qualification inspections and tests are summarized in Table 2. 4.3 Production acceptance inspection and test conditions Production acceptance inspections and tests (requirements, methods, numbers of nuts) are specified in Table 1. They shall
48、be carried out on each batch. Nuts from the batch to be tested shall be selected by simple random sampling. Each nut may be submitted to several inspections or tests. BS ISO 8641:2008 ISO 8641:2008(E) ISO 2008 All rights reserved 5 The nuts to be subjected to destructive inspections or tests may be
49、those on which non-destructive inspection or testing has been carried out. If a more stringent inspection is deemed necessary, all or part of the qualification inspections and tests may be performed during the production acceptance inspections and testing. In this case, the number of nuts submitted is the same as that submitted for qualification inspections and tests. Batches declared unacceptable after the production acceptance inspections and tests shall b
