ISO-6157-3-1988.pdf
INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATlONALE DE NORMALISATION MEWYHAPOAHAR OPrAHM3AWl I-IO CTAHAPTM3Al#lM Fasteners - Surface discontinuities - Part 3: Bolts, screws and studs for special requirements - product grades A and B; - nominal lenghts I 10d (or longer if specified); - property class 12.9; - property classes 8.8, 9.8 and 10.9 when specified in product standards or agreed between supplier and purchaser. 1.2 Where the permissible limits for surface discontinuities indicated in clause 3 occur, the minimum values for the mechanical and functional properties specified in IS0 898-l should still be met. When fatigue strength requirements are specified, the fatigue strength should not be lower than that obtained on bolts without defects taken from the same lot. NOTES 1 The figures in clause 3 are examples only. They apply correspond- ingly also to other types of bolts, screws and studs. 2 The individual figures show the surface discontinuities exaggerated in some cases for clarity. 2 References IS0 468, Surface roughness - Parameters, their values and general rules for specifying requirements. IS0 898-1, Mechanicalproperties of fasteners - Part I: Bolts, screws and studs, IS0 2859, Sampling procedures and tables for inspection by attributes. IS0 3269, Fasteners - Acceptance inspection. 3 Types, causes, appearance and 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 overstress- ing the metal during forging or other forming operations, or during heat treatment. Where parts are subjected to significant reheating, cracks usually are discoloured by scale. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6167-3 : 1666 (E) 3.1.1 Quench cracks Cause Appearance Limits Quench cracks of any depth, any length, or in any location are not permitted. 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. Cause Appearance Quench crack circum- Quench crack at corner of head Quench crack across washer face and to depth of washer face thickness Quench crack across top of head. Usually an extension of crack in shank or side of head uench crack at root Quench crack, section I-A at crest of thread missing b iJ Quench crack extending g 0,04d, (with two or more forging bursts, one of which may extend to 0,0 0,04d, (with two or more forging shear bursts, one of which may extend to 0,08dJ. 1) s = width across flats 2) d = nominal thread diameter 3) d, = head or flange diameter Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO6157-3:1966 (El 3.1.5 Forging cracks in socket head screws Appearance Cracks in the periphery, in the top surface and on the indented portion (hexagon socket) may occur on the inner and outer faces due to cut-off of wire section, shear and compressive stress during forging operations and countersinking of head. A+- Permissible L Not permissible 5 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 61!57-3 : 1988 (E) 6 Appearance (continued) Permissible depths : r Permissible Not permissible - potential intersecting discontinuities of key engagement (bottom of socket) transverse discontinuities D hj 0,03dkt): 0,13 mm max. h2 0,06dk: 1,6 mm max. in the fillet area Permissible 1) dk = head diameter 2) t = key engagement socket depth No cracks permissible LNot permissible - bottom of socket or within 0,3t of bottom of socket Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6167-3 : 1966 (El Limits Cracks extending from the socket to the outer face and cracks with a traverse indicating a potential to intersect are not permissible. Cracks within 0,3t of the bottom of the socket are not permissible. Cracks located elsewhere in the socket are permissible, provided that they do not exceed a length of 0,25t and a depth of 0,03dk (0,13 mm max.). One crack in the longitudinal direction with a depth not exceeding 0,03dk (0,13 mm max.) at the head/shank intersection and on the top of the head is permissible. Longitudinal cracks with a depth not exceeding 0,06dk (I,6 mm max.) located in the periphery are permissible. 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 I Seams and laos are inherent in the raw material from which fasteners are made. Appearance Lap or seam, usually straight or smooth curved line discontinuity running longitudinally : i I - I- L Seam I Limits Permissible depth : 0,015dl) + 0,l mm : 0,4 mm max. If laps or seams extend into the head, they shall not exceed the permissible limits for width and depth specified for bursts (see 3.1.3). 1) d = nominal thread diameter 7 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO6167-3:1966(E) 3.3 Voids A void is a shallow 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. Appearance Limits Depth, h, of voids: h 0,020: 0,25 mm max. Area of all voids: The combined surface area of all voids on the bearing face shall not exceed 5 % of the total area. 1) d = nominal thread diameter Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6167-3 : 1966 (El 3.4 Folds A fold is a doubling over of metal which occurs at the surface of the fastener during forging. Cause Folds are produced by material displacements due to lack of congruence of forms and volumes of the single foraina steos. Limits Permissible, I typical “clover leaf” fold in non-circular shoulder fastener Permissible, at the intersection between flange and driving part Permissible, at the surface of the bolt end Permissible, fold at exterior corner Not permissible, fold at interior corner- / Permissible, fold rat exterior corner Folds at interior corners at or below the bearing surface are not permissible, unless specifically permitted in this part of IS0 6157 or in the product standard. Folds at exterior corners are permissible. 3.5 Tool marks Tool marks are longitudinal or circumferential grooves of shallow depth. Cause Tool marks are produced by the movement of manufacturing tools over the surface of the bolt or screw. Appearance Tool mark 7 Permissible fool mark from trimming operation- Limits I Tool marks produced by machining in the shank, fillet or bearing surface shall not exceed a surface roughness of R, = 3.2 urn when tested in accordance with IS0 466. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 61R-3 : 1666 (E) 3.6 Laps on the thread A lap is a fold-over of metal in the thread. Laps generally show a pattern of consistency between the same product, that is laps will be identically located and tiith the same direction of traverse between all products. Cause Folds and laps on the thread occur during cold-forming of the thread by rolling. Appearance Laps and seams not permissible - Load direction Major diameter Permissible laps and seams irregularities Limits I) HI = depth of thread Laps of any depth or length are not permitted in the following places: - at the root of the thread; - at the loaded flank of screw thread below the pitch diameter, even if they start beyond the pitch dia- meter. The following laps are permissible : - laps in the crest of the threads of 0,25 H, max.; - crest of the threads not entirely rolled out, maximum half a turn on one thread; - laps below the pitch diameter, if they run on the non-loaded flank towards the major diameter and not deeper than 0,25 HI and not longer than half a turn on one thread. 3.7 Damages Damages are indentations of any surface of a bolt or screw. Cause Damages, for example dents, scrapes, nicks and gouges, are produced by external action during manufacture and handling of bolts and screws, for example during loading. Appearance No precise geometrical shape, location or direction, identifiable as external action. Limits Damages as described above shall not cause rejection unless it can be shown that Dents, scrapes, nicks and gouges on the first three threads shall be such that they allow the screwing on of a go-ring gauge with torque values of 0,001 d3 max., in newton metres. A specific agreement on packaging, for example, may be necessary in order to avoid damage during transport. 10 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6X9-3 : 1966 (E) - - 9; d - z 0 - t 0 - - L , g - 4 0 - w 0 - B 0 - - - J 0 - ri d 3 0 - - - Ki 0 - iG d - 3J 0 - uJw 9 1 ueq1 eJolu IOU JalauJe!p peaq x 90 0 JeBJq s! Jahaqa!qM UJI EL 0 Jo Ja,awe!p peay x 0 layoos 40 yldap x gz o 9 - - T. - Jatawe!p a6uelJ Jo peaq x po o Jo Ja$awe!p afiuey JO peaq x 80 0 saoeyns 6U!l&WaJM JO4 SZO IJ + WUJ gzz o - 3 d - (0 - CD - - * d - z - e - - 8 0 - 2 - f! - - 2 0 - g - s - =t 0 - 8 - 83 d - M M c, - R R - N. - 63 - 8 - m - - - 11 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6167-3 : 1988 (El 4 Inspection and evaluation procedure suitable tests, e.g. magnetic techniaues or eddv current. If no For the acceptance inspection procedure, see IS0 326% Sur- face coatings shall be removed before examination if identifi- cation of the surface discontinuities is impaired. defective product is found the lot shall be accepted (see also 4.4). If defective products are found these shall form the lot size for the procedures given in 4.3. NOTE - The 1984 edition of IS0 3269 gives no specifications on sampling plans for surface discontinuities of fasteners. Until this has 4.3 Destructive testing 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 IS0 6167. The purchaser may use the inspection procedure specified in this 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 specifi- cation is disputed, unless some other acceptance procedure has been agreed between the manufacturer and the purchaser at the time of ordering the fasteners. If defective products are detected by the procedures given in 4.2, then a secondary sample shall be taken from the defective products, in accordance with table 3 in the annex, consisting of the products indicating the most serious defects and sectioned at W 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. 4.2 Non-destructive testing A random sample shall be taken from the lot in accordance with table 2 in the annex and subjected to either visual tests or other If on the destructive test any product is found with forging cracks, bursts, seams and laps, voids, tool marks or damages which exceed the allowable limits as specified for the applicable type of discontinuity, the lot shall be subject to rejection. 12 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/21/2007 09:08:37 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 6157-3 : 1666 (E) Annex Sampling plan for surface discontinuities (This annex forms an integral part of this standard.) Sampling for surface discontinuities shall be carried out using the sample sizes given in table 2 and using the principles and procedures given in clause 4. Table 2 - Sample sizes for visual and non-destructive testing Lot sizel) Sample size N n N 1200 20 1201 N 10000 32 10001 N 35000 50 35001 N 150000 80 I 1) Lot size is the number of products of the same type, size and property class submitted for inspection at one time. NOTE - The sample sizes are based on special inspection level S-4 specified in IS0 2859. Table 3 - Secondary sample sizes for destructive testing Number of defective products Secondary in the sample sample size N n N 8 2 9N15 3 16 N 25 5 26Nt5O 8 5lN80 13 NOTE - The secondary sample sizes are based on general inspection level II specified in IS0 2859. 13 Copyright International Organization for Standardization Provided by IHS un
