1、BS ISO 8641:2008ICS 49.030.30NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDAerospace Self-locking nuts withmaximum operatingtemperature greaterthan 425 degreesC ProcurementspecificationThis British Standardwas published underthe authority of theStandards Polic
2、y andStrategy Committee on 30September 2008 BSI 2008ISBN 978 0 580 55583 1Amendments/corrigenda issued since publicationDate CommentsBS ISO 8641:2008National forewordThis British Standard is the UK implementation of ISO 8641:2008.The UK participation in its preparation was entrusted to TechnicalComm
3、ittee ACE/12, Aerospace fasteners and fastening systems.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Complianc
4、e with a British Standard cannot confer immunityfrom legal obligations.BS ISO 8641:2008Reference numberISO 8641:2008(E)ISO 2008INTERNATIONAL STANDARD ISO8641Second edition2008-09-01Aerospace Self-locking nuts with maximum operating temperature greater than 425 C Procurement specificationAronautique
5、et espace crous freinage interne dont la temprature maximale dutilisation est suprieure 425 C Spcification dapprovisionnement BS ISO 8641:2008ISO 8641:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed b
6、ut 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 Secretariat accepts no liability in this
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8、se 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 publication may be reproduced or utilized in
9、 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 20 Tel. + 41 22 749 01 11 Fax + 41 22
10、 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedBS ISO 8641:2008ISO 8641:2008(E) ISO 2008 All rights reserved iiiContents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 2 4 Quality assurance. 4 4.1 General.
11、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 5.1.3) 21 Annex B (informative) Cross-
12、sectional area and formulae for axial loads (see Table 3) 22 BS ISO 8641:2008ISO 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 bodies). The work of preparing Internation
13、al 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 and non-governmental, in liaison with ISO,
14、 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, Part 2. The main task of technical comm
15、ittees 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 casting a vote. Attention is drawn to the p
16、ossibility 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, Subcommittee SC 4, Aerospace fastener syste
17、ms. This second edition cancels and replaces the first edition (ISO 8641:1987) which has been technically revised. BS ISO 8641:2008INTERNATIONAL STANDARD ISO 8641:2008(E) ISO 2008 All rights reserved 1Aerospace Self-locking nuts with maximum operating temperature greater than 425 C Procurement speci
18、fication 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, provided that reference is made to this Internat
19、ional 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 edition of the referenced document (including
20、 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 inspection by attributes Part 1: Sampling s
21、chemes 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: Limit dimensions for bolts and nuts ISO 74
22、03, 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 greater than 425 C Test methods ISO 8788, Aer
23、ospace 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, 1 210 MPa (at ambient temperature)/730 C
24、, 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 8641:2008ISO 8641:2008(E) 2 ISO 2008 All rights r
25、eserved3 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 and temperature classes) NOTE The definition
26、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 quantity of some commodity manufactured or p
27、roduced 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 the course of the same production cycle, f
28、ollowing 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 seam open surface defect resulting from exten
29、sion 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 These particles can be isolated or arranged in
30、 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 the function of a major end item BS ISO 864
31、1:2008ISO 8641:2008(E) ISO 2008 All rights reserved 33.9 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 is not likely to reduce materially the usabil
32、ity 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 in order to obtain information and possibly
33、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 simple random sampling sampling of n items from a
34、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 of sampling inspection, can be considered satisf
35、actory 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 relatively low probability of acceptance NOTE 1 It is th
36、e 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 consumers risk of 10 %. 3.15 self-locking torque
37、 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 including the end chamfer) 3.16 seating torque ti
38、ghtening 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 number (supplementary information taken from IS
39、O 2859-1). BS ISO 8641:2008ISO 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 after the axial load in the assembly has been remo
40、ved 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 appropriate wrench from being used and preclude re
41、-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 to a recognized quality management system. The ce
42、rtification 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 the bolts shall be granted by the Certification
43、 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 representative of the actual conditions of use, wi
44、th 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 Qualification inspection and test conditions Qualificati
45、on 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 reduced, or qualification of a nut granted, wit
46、hout 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 the supplier or the manufacturing conditions have
47、 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 be carried out on each batch. Nuts from the batc
48、h to be tested shall be selected by simple random sampling. Each nut may be submitted to several inspections or tests. BS ISO 8641:2008ISO 8641:2008(E) ISO 2008 All rights reserved 5The nuts to be subjected to destructive inspections or tests may be those on which non-destructive inspection or testi
49、ng 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 be submitted for re-inspection or testing only after a
