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1、BRITISH STANDARD AEROSPACE SERIES BS 2A 293:2005 Procurement of self-locking nuts with non-metallic locking elements Metric series Specification ICS 49.030.30 ? Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2A 293:2005 This British Stan
2、dard was published under the authority of the Standards Policy and Strategy Committee on 22 February 2005 BSI 22 February 2005 The following BSI references relate to the work on this British Standard: Committee reference ACE/12 Draft for comment 03/317781 DC ISBN 0 580 45229 8 Committees responsible
3、 for this British Standard The preparation of this British Standard was entrusted to Technical Committee, ACE/12, Aerospace fasteners and fastening, upon which the following bodies were represented: British Coatings Federation Ltd. Civil Aviation Authority, Airworthiness Energy Institute Ministry of
4、 Defence, UK Defence Standardization Society of British Aerospace Companies Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2A 293:2005 BSI 22 February 2005 i Contents Page Committe
5、es responsibleInside front cover Forewordii 1Scope1 2Normative references1 3Terms and definitions1 4Requirements and test methods3 5Quality Assurance and product qualification testing approvals9 6Packing, packaging and labelling10 7Inspection10 8Production acceptance test report10 Annex A (normative
6、) Axial loads and torque values for thread sizes M8 1.25, M10 1.5 and M12 1.517 Bibliography19 Table 1 Qualification approval testing requirements for self-locking nut samples11 Table 2 Qualification and production acceptance tests12 Table 3 Discontinuity depths12 Table 4 Axial load values 100 % axi
7、al load test13 Table 5 Maximum assembly and wrench torque test values14 Table 6 Maximum locking torque, minimum breakaway torque, assembly torque (vibration), push out and torque out values15 Table 7 Classification of defects15 Table 8 Sampling data for visual and dimensional characteristics16 Table
8、 9 Sampling data for mechanical and metallurgical characteristics16 Table 10 Contaminants16 Table A.1 Maximum assembly and wrench torque test values for thread sizes M8 1.25, M10 1.5 and M12 1.517 Table A.2 Axial load values for thread sizes M8 1.25, M10 1.5 and M12 1.517 Licensed Copy: sheffieldun
9、sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2A 293:2005 ii BSI 22 February 2005 Foreword This British Standard was prepared by Technical Committee ACE/12. It supersedes BS A 293:1983, which is withdrawn. BS 2A 293 is intended primarily for use in conjunction wi
10、th those “A” series British Standard aerospace specifications in which conformity to this standard is a specific requirement. This edition introduces technical changes in line with test methods BS 2A 295:2000 and harmonizes the procurement and testing of the metric series non-metallic self-locking n
11、uts with the equivalent Unified series nuts contained in BS 3A 125 to 3A . It may also be applied to other aerospace metric threaded fasteners if required by the relevant specification, drawing, contract or order. This standard invokes: a) quality assurance approval of the manufacturer; and b) produ
12、ct qualification testing approval. Annex A is included in this standard to provide information on the axial loads and torque values for thread sizes M8 1.25, M10 1.5 and M12 1.5. When there is no further requirement for these sizes, Annex A will be deleted by amendment. This publication does not pur
13、port to include all the necessary provisions of a contract. Users are responsible for its 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 and ii,
14、pages 1 to 19 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2A 293:2005 BSI 22 February 2005 1 1 Scope This British Stand
15、ard specifies the requirements for the procurement of self-locking nuts with non-metallic locking elements. This standard invokes product qualification testing requirements and quality assurance approval procedures for manufacture of aerospace standard parts. This standard is intended primarily for
16、use with “A” series British Standard aerospace standards for metric self-locking nuts with non-metallic locking elements. It is also applicable to other aerospace self-locking nuts if required by the relevant drawing, contract or order. NOTEWhere the requirements of the nut standard or drawing diffe
17、r from this standard, they take precedence over the requirements of this standard. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the cited edition applies. For undated references, the latest edition of the
18、 referenced document (including any amendments) applies. BS 1134, Method for the assessment of surface texture. BS 1595-1, Propan-2-ol (isopropyl alcohol) for industrial use Part 1: Specification for propan-2-ol (isopropyl alcohol). BS A 352-2/ISO 5855-2, MJ threads Part 2: Limit dimensions for bolt
19、s and nuts. BS 2A 295/ISO 7481, Methods of test for self-locking nuts with maximum operating temperature less than or equal to 425C. BS 3A 125 to 3A ., Specification for stiffnuts (Unified threads) for aircraft. BS EN 9100, Aerospace series Quality management systems Requirements (based on ISO 9001:
20、2000) and Quality systems Model for quality assurance in design, development, production, installation and servicing (based on ISO 9001:1994). 3 Terms and definitions For the purposes of this British Standard the following terms and definitions apply. 3.1 self-locking nut with non-metallic locking e
21、lement self-contained unit which consists of a nut body surmounted by a non-metallic locking element which imposes friction between itself and the male screw thread upon which it is mounted 3.2 nut body portion of the self-locking nut containing the screw thread 3.3 locking element non-metallic port
22、ion of the self-locking nut designed to impose friction between itself and the male screw thread with which it is engaged NOTEThe locking element does not operate by means of a separate movement as a result of installation and does not depend upon pressure on the bearing surface for the locking acti
23、on. 3.4 maximum locking torque highest torque to overcome the friction encountered in any assembly or removal cycle with no axial load on the nut 3.5 minimum breakaway torque torque required to start nut or bolt rotation from a fixed position during any removal cycle with no axial load on the nut Li
24、censed Copy: sheffieldun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2A 293:2005 2 BSI 22 February 2005 3.6 wrench torque minimum torque which the driving configuration of the nut has to withstand without any permanent deformation which would interfere with the
25、 appropriate wrench and preclude the reuse of the nut 3.7 permanent set test measure of the performance of a nut on a minimum mandrel after having been subjected to a single assembly and removal cycle on a maximum stud 3.8 reusability test test to measure the torque required to remove a self-locking
26、 nut from a standard test bolt after a specified number of assembly and removal cycles 3.9 production lot lot of finished nuts which have the basic part number and diameter, the individual elements of which have been fabricated by the same process from a single material batch, and which have been he
27、at treated together to the same specified condition and produced as one continuous run 3.10 inspection lot lot of nuts from a single production lot, of the same part number, which completely defines the nut 3.11 Discontinuities 3.11.1 crack rupture in the material which may extend in any direction a
28、nd which may be intercrystalline or transcrystalline in character 3.11.2 seam longitudinal surface defect in the form of an unwelded open fold in the material 3.11.3 lap surface defect caused by folding over metal fins or sharp corners and then rolling or forging them into the surface 3.12 random sa
29、mple sample taken in such a manner that each unit in the inspection lot has the same chance of being the first unit in the random sample; and, after the first unit in the sample is taken, each of the remaining units in the inspection lot has the same chance of being the second unit in the sample; an
30、d so on 3.13 acceptable quality level AQL maximum percentage defective (or maximum number of defects per hundred units) that, for purposes of sampling inspection, can be considered acceptable as a process average 3.14 limiting quality LQ magnitude of percentage defective, greater than the AQL, which
31、, in accordance with the operating characteristic of the sampling/inspection plan, the purchaser runs a specified risk of accepting NOTEIn this standard the LQ corresponds to a purchasers risk of 10 %. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy,
32、 (c) BSI BS 2A 293:2005 BSI 22 February 2005 3 4 Requirements and test methods 4.1 Introduction The technical requirements and test methods given in 4.2, 4.3, 4.4, 4.5 and 4.6 complement the requirements of the self-locking nut standard or drawing, but can supplement the requirements of the material
33、 specification. Table 1 gives the testing for each characteristic of the self-locking nut sample necessary for qualification approval. Table 2 summarizes the testing required for both qualification and production acceptance testing. All tests shall be carried out at ambient temperature unless otherw
34、ise specified in a particular test method. NOTE 1A nut is considered to be assembled when a minimum of two full male threads plus the chamfer extend beyond the friction element of the nut. NOTE 2The removal cycle is considered complete when the friction element is disengaged. Licensed Copy: sheffiel
35、dun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2A 293:2005 4 BSI 22 February 2005 SubclauseCharacteristicTechnical requirementInspection and test methodQ/AaSample size 4.2MaterialsThe nut shall be made from the material specified by the nut standard or drawing
36、. As stated in the material specification. 4.3Dimensions 4.3.1GeneralThe dimensions of the finished nut shall comply with the nut standard or drawing. All dimensions shall be controlled by the manufacturers quality system. Q60 (100 %) ATable 7 and Table 8 4.3.2ThreadsThe threads shall comply with th
37、e requirements specified by the nut standard or drawing. Q60 (100 %) ATable 7 and Table 8 4.3.3SquarenessThe bearing surface of the nut shall be square to the axis of the thread within the tolerance specified by the nut standard or drawing. Bearing surface squareness test, 3.2 of BS 2A 295:2000. Q60
38、 (100 %) ATable 7 and Table 8 4.4Manufacture 4.4.1Nut bodiesNut bodies shall be produced by machining from bar or by a hot or cold forging process. The method of manufacture shall be defined by control documentation to the satisfaction of the appropriate airworthiness authority. 4.4.2Heat treatment
39、The parts shall be heat treated as necessary, to satisfy the requirements of this specification. 4.4.3Surface texture The surface texture shall be as specified by the nut standard or drawing prior to protective treatment. BS 1134Q3 ATable 7 and Table 8 4.4.4Surface protection Surfaces shall be coate
40、d as specified by the nut standard or drawing. Relevant coating specification. Q3 ATable 7 and Table 8 4.4.5LubricationSurfaces shall be coated as specified by the nut standard or drawing. Relevant coating specification. Q3 ATable 7 and Table 8 a Q is the qualification approval test requirement and
41、A is the production acceptance test requirement. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2A 293:2005 BSI 22 February 2005 5 SubclauseCharacteristicTechnical requirementInspection and test methodQ/AaSample size 4.5Metallurgical pro
42、perties 4.5.1Discontinuities Nuts shall be examined for discontinuities. Nuts having discontinuities exceeding the limitations specified in Table 3 shall be rejected. Non-corrosion resisting steel nuts shall be magnetically inspected by both longitudinal and circular methods. The combined method is
43、permissible. Q60 (100 %) ATable 7 and Table 8 Care shall be exercised to avoid confusing cracks with other discontinuities (see 3.11). Cracked parts shall be rejected. Nuts made from non-magnetic material shall be subjected to a visual examination of magnification 10. Parts showing indications which
44、 are considered cause for rejection shall be subjected to metallographic examination at a magnification of 100. ATable 9, column B 4.5.2Magnetic permeability and residual magnetism (applicable to corrosion resisting steel nuts only) The magnetic permeability of corrosion resisting steel nuts shall b
45、e as specified in the material specification of the product. Residual magnetism shall not exceed 0.5 gauss. Magnetic field indicator of suitable calibration, used in accordance with the manufacturers instructions. Q3 ATable 9, column B NOTEThe same test sample may be utilized for more than one test
46、provided that none of the characteristics of the sample are altered during the examination procedure. a Q is the qualification approval test requirement and A is the production acceptance test requirement. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 14:34:33 GMT+00:00 2006, Uncontrolled C
47、opy, (c) BSI BS 2A 293:2005 6 BSI 22 February 2005 SubclauseCharacteristicTechnical requirementInspection and test methodQ/AaSample size 4.6Product performance 4.6.1Axial tensile strength Nuts shall withstand the minimum tensile load appropriate to their strength classification as defined in the nut
48、 standard or drawing, and as specified in Table 4. Nuts shall support the relevant axial tensile strength load without rupture. 3.3 of BS 2A 295:2000. This test shall be carried out at ambient temperature. Q3 ATable 9, column B 4.6.2Permanent setThe nut shall not exceed the maximum permissible locki
49、ng torque during assembly onto a maximum mandrel as specified in Table 6. 3.11 of BS 2A 295:2000Q3 ANil During removal from a minimum mandrel the nut shall not exhibit a breakaway torque less than that specified in Table 6. 4.6.3Accelerated environmental reusability Nuts shall meet the minimum breakaway torque and the maximum locking torque specified in Table 6 after each of four cycles of loaded heat soak. Each cycle s