1、BRITISH STANDARD BS EN 26157-1:1992 ISO 6157-1: 1988 Fasteners Surface discontinuities Part 1: Bolts, screws and studs for general requirements The European Standard EN 26157-1:1991 has the status of a British StandardBSEN26157-1:1992 This British Standard, having been prepared under the directionof
2、 the General Mechanical Engineering Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 1 May 1992 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference GME/9 Draft announced in BSI News December 1991
3、ISBN 0 580 20813 3 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: Austria Oesterreichisches Normungsinstitut Belgium Institut belge de
4、normalisation Denmark Dansk Standardiseringsraad Finland Suomen Standardisoimisliito, r.y. France Association franaise de normalisation Germany Deutsches Institut fr Normung e.V. Greece Hellenic Organization for Standardization Iceland Technological Institute of Iceland Ireland National Standards Au
5、thority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Inspection du Travail et des Mines Netherlands Nederlands Normalisatie-instituut Norway Norges Standardiseringsforbund Portugal Instituto Portugus da Qualidade Spain Asociacin Espaola de Normalizacin y Certificacin Sweden St
6、andardiseringskommissionen i Sverige Switzerland Association suisse de normalisation United Kingdom British Standards Institution Amendments issued since publication Amd. No. Date CommentsBSEN26157-1:1992 BSI 08-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii F
7、oreword 2 Text of EN 26157-1 3 National annex NA (informative) Committees responsible Inside back cover National annex NB (informative) Cross-references Inside back coverBSEN26157-1:1992 ii BSI 08-1999 National foreword This British Standard has been prepared under the direction of the General Mecha
8、nical Engineering Standards Policy Committee and is the English language version of EN 26157-1:1991, “Fasteners Surface discontinuities Part 1: Bolts, screws and studs for general requirements, published by the European Committee for Standardization (CEN). It is identical with ISO 6157-1:1988, publi
9、shed by the International Organization for Standardization (ISO). EN26157-1:1991 was produced as a result of international discussion in which the UK took an active part. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are respons
10、ible 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, theEN title page, pages 2 to 12, an inside back cover and a back cover. Thi
11、s 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.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 26157-1 October 1991 UDC 621.882.2:620.191 Descriptors: Fasteners, bolts, screws, st
12、uds, surface defects English version Fasteners Surface discontinuities Part1:Bolts,screwsand studs for general requirements (ISO 6157-1:1988) Elments de fixation Dfauts de surface Partie1: Boulons, vis et goujons dusage gnral (ISO 6157-1:1988) Verbindungselemente Oberflchenfehler Teil 1: Schrauben f
13、r allgemeine Anforderungen (ISO 6157-1:1988) This European Standard was approved by CEN on 1991-10-10. 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.
14、Up-to-date lists and bibliographical 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 u
15、nder the responsibility of a CEN 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, Nethe
16、rlands, Norway, Portugal, Spain, 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 CEN 1991 Copyright reserved to all CEN members Ref. No. EN 26157-
17、1:1991 EEN26157-1:1991 2 BSI 08-1999 Foreword In 1990, ISO 6157-1:1988 was submitted to the CENP.Q.-procedure. Following the positive result of the P.Q., CEN/BT agreed to submit ISO6157-1:1988 with the following modifications to Formal Vote. In the French version, replace: “boulon” by “vis” “boulon,
18、 vis” by “vis” In accordance with the Common CEN/CENELEC Rules, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and Unit
19、ed Kingdom. Contents Page Foreword 2 1 Scope and field of application 3 2 References 3 3 Types, causes, appearance and limits ofsurfacediscontinuities 3 4 Inspection and evaluation procedure 10 Annex Sampling plan for surface discontinuities 11 Table 1 Samples sizes for visual and non-destructive te
20、sting 11 Table 2 Secondary sample sizes for destructivetesting 11EN26157-1:1991 BSI 08-1999 3 1 Scope and field of application 1.1 This part of ISO 6157 establishes limits for various types of surface discontinuities on bolts, screws and studs for general requirements. It applies to bolts, screws an
21、d studs with nominal thread diameters5mm and larger; product grades A and B; property classes up to and including 10.9, unless otherwise specified in product standards or agreed between supplier and purchaser. 1.2 Limits for surface discontinuities on bolts, screws and studs for special requirements
22、 (e.g. automatic assembly) are laid down in ISO6157-3. When the engineering requirements of the application necessitate that surface discontinuities on bolts, screws and studs be more closely controlled, it should be specified in the respective product standard, or the purchaser shall specify the ap
23、plicable limits in the inquiry and purchase order. 1.3 Where the permissible limits for surface discontinuities indicated in clause3 occur, the minimum values for the mechanical and functional properties specified inISO898-1 should still be met. NOTE 1The figures in clause3 are examples only. They a
24、pply correspondingly also to other types of bolts, screws and studs. NOTE 2The individual figures show the surface discontinuities exaggerated in some cases for clarity. 2 References ISO 468, Surface roughness Parameters, their values and general rules for specifying requirements. ISO 898-1, Mechani
25、cal properties of fasteners Part 1: Bolts, screws and studs. ISO 2859, Sampling procedures and tables for inspection by attributes. ISO 3269, Fasteners Acceptance inspection. 3 Types, causes, appearance and limits of surface discontinuities 3.1 Cracks A crack is a clean (crystalline) fracture passin
26、g 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 heat treatment. Where parts are subjected to significant reheating, cracks usually are discolou
27、red by scale.EN26157-1:1991 4 BSI 08-1999 3.1.1 Quench cracks 3.1.2 Forging cracks Cause Quench cracks may occur during hardening due to excessively high thermal and transformation stresses. Quench cracks usually follow an irregular and erratic course on the surface of the fastener. Appearance Limit
28、s Quench cracks of any depth, any length, or in any location are not permitted. Cause Forging cracks may occur during the cut-off or forging operations and are located on the top of the head of screws and bolts and on the raised periphery of indented head bolts and screws. Appearance Limits Length,
29、l, of forging cracks: l u d a Depth or width, b, of forging cracks: b u 0,04 d a d = nominal thread diameterEN26157-1:1991 BSI 08-1999 5 3.1.3 Forging bursts Cause Forging bursts may occur for example during forging on the flats or corners of the heads of bolts and screws, at the periphery of flange
30、d or circular head products or on the raised periphery of indented head bolts and screws. Appearance Limits Hexagon head screws No forging burst in the flats of hexagon bolts and screws shall extend into the crown circle on the top of the head surface (chamfer circle) or into the underhead bearing s
31、urface. Forging bursts occurring at the intersection of two wrenching flats shall not reduce the width across corners below the specified minimum. Forging bursts in the raised periphery of indented head bolts and screws shall not exceed a width of0,06d aor have a depth extending below the indented p
32、ortion. Circular head screws Flanges of bolts and screws and peripheries of circular head screws may have forging bursts, but they shall not exceed the following limits: Width of forging bursts: 0,08d c b(with only one forging burst); 0,04d c (with two or more forging bursts, one of which may extend
33、 to0,08d c ). a d = nominal thread diameter b d c= head or flange diameterEN26157-1:1991 6 BSI 08-1999 3.1.4 Shear bursts Cause Shear bursts may occur, for example during forging, frequently at the periphery of products having circular or flanged heads, and are located at approximately 45 to the pro
34、duct axis. Shear bursts may also occur on the sides of hexagon head products. Appearance Limits Hexagon head screws No shear burst in the flats of hexagon bolts and screws shall extend into the crown circle on the top of the head surface (chamfer circle) or into the underhead bearing surface. Shear
35、bursts, occurring at the intersection of two wrenching flats, shall not reduce the width across corners below the specified minimum. Shear bursts in the raised periphery of indented head bolts and screws shall not exceed a width of0,06d aor have a depth extending below the indented portion. Circular
36、 head screws Flanges of bolts and screws and peripheries of circular head products may have shear bursts, but shall not exceed the following limits: Width of shear bursts: 0,08d c b(for only one shear burst); 0,04d c(with two or more forging shear bursts, one of which may extend to 0,08d c ). a d =
37、nominal thread diameter b d c= head or flange diameterEN26157-1:1991 BSI 08-1999 7 3.2 Raw material seams and laps A seam or lap is a narrow, generally straight or smooth curved line discontinuity running longitudinally on the thread, shank or head. Cause Seams and laps are inherent in the raw mater
38、ial from which fasteners are made. Appearance Limits Permissible depth: 0,03d a If laps or seams extend into the head, they shall not exceed the permissible limits for width and depth specified for bursts (see3.1.3). a d = nominal thread diameterEN26157-1:1991 8 BSI 08-1999 3.3 Voids A void is a sha
39、llow pocket or hollow on the surface of a bolt or screw due to non-filling of metal during forging or upsetting. Cause Voids are produced by marks and impressions due to chips (shear burrs) or by rust formation on the raw material. They are not eliminated during forging or upsetting operations. Appe
40、arance Limits Depth, h, of voids: h u 0,02 d a : 0,25 mm max. Area of all voids: The combined surface area of all voids on the bearing face shall not exceed 10% of the total area. a d = nominal thread diameterEN26157-1:1991 BSI 08-1999 9 3.4 Folds A fold is a doubling over of metal which occurs at t
41、he surface of the fastener during forging. 3.5 Tool marks Tool marks are longitudinal or circumferential grooves of shallow depth. Cause Folds are produced by material displacements due to lack of congruence of forms and volumes of the single forging steps. Appearance Limits Folds at interior corner
42、s at or below the bearing surface are not permissible, unless specifically permitted in this part of ISO 6157 or in the product standard. Folds at exterior corners are permissible. Cause Tool marks are produced by the movement of manufacturing tools over the surface of the bolt or screw. Appearance
43、Limits Tool marks produced by machining in the shank, fillet or bearing surface shall not exceed a surface roughness of R a= 3,24m when tested in accordance with ISO 468.EN26157-1:1991 10 BSI 08-1999 3.6 Damages Damages are indentations of any surface of a bolt or screw. 4 Inspection and evaluation
44、procedure For the acceptance inspection procedure, seeISO3269. Surface coatings shall be removed before examination if identification of the surface discontinuities is impaired. NOTEThe 1984 edition of ISO3269 gives no specifications on sampling plans for surface discontinuities of fasteners. Until
45、this has been completed, the applicable sampling plan is given in the Annex. 4.1 Principles The manufacturer is entitled to use any inspection procedures but due care shall be taken to ensure that products conform to this part of ISO6157. The purchaser may use the inspection procedure specified in t
46、his clause at his acceptance inspection in order to decide whether a lot of fasteners may be accepted or rejected. This procedure shall also be applied when conformance to specification is disputed, unless some other acceptance procedure has been agreed between the manufacturer and the purchaser at
47、the time of ordering the fasteners. 4.2 Non-destructive testing A random sample shall be taken from the lot in accordance with Table 1in the Annex and subjected to either visual tests or other suitable tests, e.g. magnetic techniques or eddy current. If no defective product is found the lot shall be
48、 accepted (see also 4.4). If defective products are found these shall form the lot size for the procedures given in4.3. 4.3 Destructive testing If defective products are detected by the procedures given in4.2, then a secondary sample shall be taken from the defective products, in accordance withTabl
49、e 2 in the Annex, consisting of the products indicating the most serious defects and sectioned at90 through the discontinuity where the greatest depth is expected. 4.4 Evaluation If on visual inspection any product is found with quench cracks in any location, or folds at interior corners or below the bearing surface, except “clover leaf” folds in non-circular shoulder fasteners, the lot shall be subject to rejection. If on the destructive test any product is found with forging cracks, bursts, seams and lap
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