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1、BRITISH STANDARD BS EN 493:1992 Fasteners Surface discontinuities Nuts The European Standard EN 493:1992 has the status of a British Standard UDC 621.882.3:620.191 Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 493:1992 This British S
2、tandard, having been prepared under the direction of the General Mechanical Engineering Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 October 1992 BSI 10-1999 The following BSI references relate to the work on this standard: Committe
3、e reference GME/9 Draft for comment 91/76629 DC ISBN 0 580 21075 8 Cooperating organizations The European Committee for Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries: AustriaOesterreichisc
4、hes Normungsinstitut BelgiumInstitut belge de normalisation DenmarkDansk Standardiseringsraad FinlandSuomen Standardisoimisliito, r.y. FranceAssociation franaise de normalisation GermanyDeutsches Institut fr Normung e.V. GreeceHellenic Organization for Standardization IcelandTechnological Institute
5、of Iceland IrelandNational Standards Authority of Ireland ItalyEnte Nazionale Italiano di Unificazione LuxembourgInspection du Travail et des Mines NetherlandsNederlands Normalisatie-instituut NorwayNorges Standardiseringsforbund PortugalInstituto Portugus da Qualidade SpainAsociacin Espaola de Norm
6、alizacin y Certificacin SwedenStandardiseringskommissionen i Sverige SwitzerlandAssociation suisse de normalisation United KingdomBritish Standard Institution Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Unco
7、ntrolled Copy, (c) BSI BS EN 493:1992 BSI 10-1999i Contents Page Cooperating organizationsInside front cover National forewordii Foreword2 1Scope3 2Normative references3 3Types, causes, appearance and limits of surface discontinuities3 4Inspection and evaluation procedure13 Annex A (normative) Widen
8、ing test on nuts14 Annex B (normative) Cone proof load test on nuts14 National annex NA (informative) Committees responsibleInside back cover National annex NB (informative) Cross-referencesInside back cover Figure A.1 Test mandrel for widening of nuts up to 6 % (1,06 d) or up to 4 % (1,04 d) respec
9、tively15 Figure A.2 Test assembly16 Figure B.1 Conical washer16 Figure B.2 Test assembly16 Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 493:1992 ii BSI 10-1999 National foreword This British Standard has been prepared under the dire
10、ction of the General Mechanical Engineering Standards Policy Committee and is the English language version of EN 493:1992 Fasteners Surface discontinuities Nuts, published by the European Committee for Standardization (CEN). EN 493:1992 was produced as a result of international discussion in which t
11、he United Kingdom took an active part. BS EN 493:1992 in conjunction with BS EN 26157-1:1992 and BS EN 26157-3:1992 form a series of standards that cover the surface discontinuities of fasteners. A British Standard does not purport to include all the necessary provisions of a contract. Users of Brit
12、ish 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 comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 16, an inside back c
13、over 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. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUR
14、OPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 493:1992 May 1992 UDC 621.882.3:620.191 Descriptors: Fasteners, nuts: Fasteners, appearance, surface defects, limits English version Fasteners Surface discontinuities Nuts Elments de fixation Dfauts de surface Ecrous Verbindungselemente Oberflchenfeh
15、ler Muttern This European Standard was approved by CEN on 1992-05-15. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographi
16、cal references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN
17、member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain,
18、Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1997 Copyright reserved to CEN members Ref. No. EN 493:1992 E Licensed Copy: sheffieldun sheffield
19、un, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 BSI 10-1999 2 Foreword This European Standard has been drawn up by Technical Committee CEN/TC 185 “Threaded and non-threaded mechanical fasteners and accessories” and was submitted to the Unique Acceptance Procedure.
20、National standards identical to this European Standards shall be published at the latest by 1992-11-30 and conflicting national standards shall be withdrawn at the latest by 1992-11-30. In accordance with the CEN/CENELEC Common Rules, the following countries are bound to implement this European Stan
21、dard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992
22、 BSI 10-19993 1 Scope 1.1 This European Standard establishes limits for various types of surface discontinuities on nuts with: nominal thread diameters from 5 up to and including 39 mm; product grade A and B; all property classes according to EN 20898-2, ISO 898-6 and ISO 2320; unless otherwise spec
23、ified in product standards or by the purchaser. 1.2 In case of the permissible limits for surface discontinuities indicated in clause 3, properties according to EN 20898-2, ISO 898-6 and ISO 2320 as appropriate must be satisfied. In addition, the dimensional requirements of the appropriate product s
24、tandard must be satisfied. Notes: The figures in clause 3 are examples only. They also apply correspondingly to other types of nuts. The individual figures show the surface discontinuities exaggerated in some cases for clarity. 2 Normative references This European Standard incorporates by dated or u
25、ndated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only wh
26、en incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. ISO 468, Surface roughness Parameters, their values and general rules for specifying requirements. EN 20898-2, Mechanical properties of fasteners Part 2: Nuts with specif
27、ied proof load values. ISO 898-6, Mechanical properties of fasteners Part 6: Nuts with specified proof load values Fine pitch thread. ISO 2320, Prevailing torque type steel hexagon nuts Mechanical and performance properties. ISO 3269, Fasteners Acceptance inspection. 3 Types, causes, appearance and
28、limits of surface discontinuities 3.1 Cracks A crack is a clean (crystalline) fracture passing through or across the grain boundaries and may possibly follow inclusions of foreign elements. Cracks are normally caused by overstressing the metal during forging or other forming operations, or during he
29、at treatment or may have been present in the raw material. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 4 BSI 10-1999 3.1.1 Quench cracks CauseQuench cracks may occur during heat treatment. Such cracks usually appear as irregu
30、lar and branched pathways on any surface of the nut. Appearance LimitsQuench cracks of any depth, any length or in any location are not permitted. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 BSI 10-19995 3.1.2 Forging cracks
31、and inclusion cracks CauseForging cracks may occur during the cut-off or forging operations and are located only in the top and bottom face of the nuts or in the intersection of the face and flat. Inclusion cracks are caused by non-metallic inclusions inherent in the raw material. Appearance LimitsC
32、racks located in the top and bottom faces shall be permitted provided that: there are no more than two forging cracks which extend across the full width of the bearing face neither of which shall exceed a depth of 0,05 d. In the case of flange nuts, cracks in the area between s and dW are not permit
33、ted; no crack extends into the tapped hole beyond the first full thread; no crack in the first full thread exceeds a depth of 0,5 H1. d = nominal thread diameter dw = external diameter of the bearing face H1 = effective thread height H1 = 0,541 P P= pitch of thread s = width across flats Licensed Co
34、py: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 6 BSI 10-1999 3.1.3 Cracks in the locking element of all metal prevailing torque type nuts 3.1.4 Cracks in the washer retainer A crack in the washer retainer is an opening in a lip or hub of m
35、etal used for securing a washer on a nut. CauseCracks in the locking element of all metal prevailing torque type nuts may occur during cut off, forging or deflecting process and are either on the external or internal face. Appearance LimitsCracks in the locking element resulting from the forging pro
36、cess shall be permitted provided that all mechanical and functional requirements are met and that: there are no more than two cracks which extend the full width of the crown circle neither of which shall exceed a depth of 0,05 d; no crack extends into the tapped hole beyond the first full thread; no
37、 crack in the first full thread exceeds a depth of 0,5 H1. Cracks in the locking element resulting from deflecting process are not permitted. d = nominal thread diameter H1 (see 3.1.2) CauseWasher retainer cracks may occur when pressure is applied to the lip or hub during assembly of the washer. App
38、earance LimitsWasher retainer cracks are permissible if limited to the contour of the lip or hub used for retaining purposes provided that the washer is securely held and able to rotate freely. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI
39、 EN 493:1992 BSI 10-19997 3.2 Shear bursts Shear bursts are open breaks in the surface of the metal. CauseShear bursts occur e.g. during forging operations on the external surfaces of nuts and at periphery of flange nuts. Shear bursts are located at approximately 45 to the axis of the nut. Appearanc
40、e LimitsNo shear burst in the flats of hexagon nuts shall extend into the bearing faces of the nut or crown circle of the flange nut. Shear bursts occurring at the intersection of two wrenching flats shall not reduce the width across corners below specified minimums. Shear bursts at the periphery of
41、 the flange of flange nuts are allowed providing they do not extend into the minimum diameter of the bearing face dw. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 8 BSI 10-1999 3.3 Bursts Bursts are open breaks in the surface
42、of the metal. CauseBursts may occur e.g. during forging operations on the external surfaces of nuts and at periphery of flanged nuts because of surface discontinuities in the raw material. Appearance LimitsIf a burst occurs in connection with a seam resulting from the raw material, the seam may exte
43、nd into the crown circle, see 3.4 but not the burst. Bursts occurring at the intersection of two wrenching flats shall not reduce the width across corners below specified minimums. No burst located at the intersection of top or bottom face with a wrenching flat shall have a width greater than 0,25 m
44、m + 0,02 s. Bursts at the periphery of the flange of flange nuts are allowed providing they do not extend into the minimum diameter of the bearing face dw and the width of the burst does not exceed 0,08 dc. dc s = = flange diameter width across flats Licensed Copy: sheffieldun sheffieldun, na, Sat N
45、ov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 BSI 10-19999 3.4 Seams A seam is a longitudinal surface discontinuity in the form of an unwelded open fold in the material. CauseSeams are usually inherent in the raw material from which fasteners are made. Appearance LimitsSeams
46、shall be permitted provided if a depth from the surface of 0,05 d for all thread sizes is not exceeded. d = nominal thread diameter. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 10 BSI 10-1999 3.5 Folds A fold is a doubling ov
47、er of metal which occurs at the surface of the nut during forging. CauseFolds may be produced by material displacements during forging operations on nuts at or near the intersection of diameter changes or on the top or bottom face of the nut. Appearance LimitsFolds shall be permitted except that tho
48、se located at the intersection of the flange periphery and bearing face of flange nuts shall not intrude into the bearing surface. Licensed Copy: sheffieldun sheffieldun, na, Sat Nov 04 07:47:26 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 493:1992 BSI 10-199911 3.6 Voids A void is a shallow pocket
49、 or hollow on the surface of a nut due to non-filling of metal during forging or upsetting. Causevoids are produced by marks or impressions of chips (shear burrs) or by rust formation on the raw material. They are not planished during forging or upsetting. Appearance LimitsDepth of voids: k 0,02 d: 0,25 mm max. Area of all voids: The combined surface area of all voids on the bearing face must not exceed: 5 % of the bearing surface for nuts with thread diameters up to and including 24 mm a