ISO INTERNATIONAL STANDARD 6157-3 First edition 1988-08-01 INTERNATIONALORGANIZATIONFORSTANDARDIZATION ORGANISATION INTERNATIONALE DENORMALISATION MEKAYHAPOAHAR OPTAHW3ALMR O CTAHAAPTM3ALMM Fasteners-Surfacediscontinuities- Part 3: Bolts,screwsandstudsforspecialrequirements Elementsdefixation--Defautsdesurface- Partie3:Boulons,vis et goujons pourapplicationsparticulieres Reference numbe ISO 6157-3 : 1988 (E) ISO6157-3:1988 (E) Foreword ISo (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). 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, govern- mental and 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISo Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 6157-3 was prepared by Technical Committee ISO/TC 2, Fasteners, Users should note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard implies its latest edition, unless otherwise stated. International Organizationfor Standardization,1988 Printed in Switzerland ISO6157-3:1988(E) INTERNATIONALSTANDARD Fasteners Surfacediscontinuities Part 3: Bolts, screws and studs for special requirements Scopeand fieldofapplication The individual figures show the surface discontinuities exaggerated in some cases for clarity. 1.1 This part of ISo 6157 establishes limits for various types of surface discontinuities on bolts, screws and studs for special References requirements. 2 It applies to bolts, screws and studs with ISo468,Surface roughness-Parameters,their values and general rules for specifying requirements. nominal thread diameters 5 mm and larger; product grades A and B; ISo898-1,Mechanical properties offasteners-Part1:Bolts, screws and studs. nominal lenghts I < 10d (or longer if specified); ISo2859,Samplingprocedures and tablesfor inspectionby property class 12.9; attributes. property classes 8.8, 9.8 and 10.9 when specified in product standards or agreed between supplier and ISO3269,Fasteners-Acceptance inspection. purchaser. 1.2 Where the permissible limits for surface discontinuities 3 Types,causes,appearanceandlimits indicated in clause 3 occur, the minimum values for the of surface discontinuities mechanical and functional properties specified in ISO 898-1 should still be met. 3.1 Cracks When fatigue strength requirements are specified, the fatigue strength should not be lower than that obtained on bolts A crack is a clean (crystalline) fracture passing through or without defects taken from the same lot. across the grain boundaries and may possibly follow inclusions of foreign elements. Cracks are normally caused by overstress- NOTES ing the metal during forging or other forming operations, or 1 The figures in clause 3 are examples only,They apply correspond- during heat treatment. Where parts are subjected to significant ingly also to other types of bolts, screws and studs. reheating, cracks usually are discoloured by scale. 1