1、Designation: F 788/F 788M 08Standard Specification forSurface Discontinuities of Bolts, Screws, and Studs, Inchand Metric Series1This standard is issued under the fixed designation F 788/F 788M; the number immediately following the designation indicates the yearof original adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This specifi
3、cation establishes allowable limits for thevarious types of surface discontinuities that may occur duringthe manufacture and processing of bolts, screws, and studs,including heat-treated machine screws, tapping screws, andsems (the washers of screw-washer assemblies are excluded).This specification
4、covers metric series products with nominaldiameters of 4 mm and larger and with specified minimumtensile strengths of 420 MPa and higher; and inch seriesproducts with nominal diameters of No. 5 (0.1250 in.) andlarger and with specified minimum tensile strengths of 60 000psi and higher.1.2 When the e
5、ngineering requirements of the applicationnecessitate control of surface discontinuities on bolts, screws,or studs, the purchaser shall specify conformance to ASTMSpecification F 788/F 788M, in the original inquiry and pur-chase order.1.2.1 When the engineering requirements of the applicationnecessi
6、tate that surface discontinuities on bolts, screws, andstuds be controlled within limits closer than those specified inthis specification, the purchaser shall specify the applicablelimits in the original inquiry and purchase order.1.3 The allowable limits established in this specification formetric
7、bolts, screws, and studs with nominal diameters from 4to 24 mm inclusive, are essentially identical with requirementsgiven in ISO 6157/I. There are no ISO standards for surfacediscontinuities on any inch-series products.1.4 The values stated in either SI units or inch-pound unitsare to be regarded s
8、eparately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.2. Referenced Documents2.1 ASTM Standards:2E 340 Test Method for Ma
9、croetching Metals and AlloysF 1470 Guide for Fastener Sampling for Specified Mechani-cal Properties and Performance InspectionF 1789 Terminology for F16 Mechanical Fasteners2.2 ISO Standard:3ISO 6157/I Fasteners, Surface Discontinuities on Bolts,Screws and Studs3. Ordering Information3.1 Orders for
10、bolts, screws, and studs requiring disconti-nuity control shall include the following:3.1.1 ASTM designation and date of issue of this specifica-tion.3.1.2 Special requirements, for example, closer discontinu-ity limits (1.2.1) and inspection sampling plan (6.2).4. Types of Surface Discontinuities (
11、see TerminologyF 1789 for definitions not provided)4.1 Crack4.1.1 Quench CracksTypical quench cracks are shown inFig. 1. Limits are specified in 5.2.4.1.2 Forging CracksTypical forging cracks are shown inFig. 2. Limits are specified in 5.3.4.2 BurstTypical bursts are shown in Fig. 3. Limits arespeci
12、fied in 5.4.4.2.1 Shear BurstA shear burst is an open break in themetal located at approximately a 45 angle to the product axis.Shear bursts occur most frequently at the periphery of productshaving flanged or circular heads. Shear bursts may also occuron the sides of hex-head products. Typical shear
13、 bursts areshown in Fig. 3. Limits are specified in 5.4.1This specification is under the jurisdiction of ASTM Committee F16 onFasteners and is the direct responsibility of Subcommittee F16.93 on QualityAssurance Provisions for Fasteners.Current edition approved Nov. 1, 2008. Published November 2008.
14、 Originallyapproved in 1982. Last previous edition approved in 2007 as F 788/F 788M 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summar
15、y page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoc
16、ken, PA 19428-2959, United States.4.3 SeamTypical seams are shown in Fig. 4. Limits arespecified in 5.5.4.4 FoldTypical folds are shown in Fig. 5 a, b, and c.Limits are specified in 5.6.4.5 Thread LapLimits are specified in SupplementaryRequirement S.1.1.4.6 VoidA void is a shallow pocket or hollow
17、on thesurface of a bolt or screw due to nonfilling of metal duringforging. Voids are produced by marks or impressions of chips(shear burrs) or by rust formation on the raw material. They arenot planished during forging. Typical voids are shown in Fig.6. Limits are specified in 5.7.4.7 Tool MarksTool
18、 marks are longitudinal or circumfer-ential grooves of shallow depth produced by the movement ofmanufacturing tools over the surface of the bolt or screw.Typical tool marks are shown in Fig. 7. Limits are specified in5.8.4.8 Gouge and Nickan indentation on the surface of afastener produced by impact
19、 with another fastener, or fromprocessing equipment during manufacture, handling or trans-port.5. Allowable Limits5.1 Letter DefinitionsThroughout the following require-ments, D designates the nominal size (basic major diameter ofthread) of bolts, screws, and studs, except for products withshoulders
20、, in which case D designates the largest shoulderdiameter; and Dc designates flange diameter (specified maxi-mum) or head diameter (specified maximum) of circular headproducts. For metric series products, D and Dc are in millime-tres; for inch-series products, D and Dc are in inches.5.2 Quench Crack
21、sQuench cracks of any depth, anylength, or in any location are not permitted.5.3 Forging CracksForging cracks on the top of the headof bolts and screws are permitted, provided that (a) no crackshall have a length exceeding 1.0 D, and (b) no crack shall havea width or depth exceeding 0.04 D. See Note
22、 1.NOTE 1Forging cracks within the limits of this specification may beunsightly, but do not affect the mechanical properties or functionalrequirements of the bolt.5.4 Bursts and Shear Bursts (see Note 2):5.4.1 For hex-head bolts and screws, bursts and shear burstsare permitted, provided that: (1) no
23、 burst or shear burst in theflats extends into the crown (chamfer) circle on the top of thehead or into the underhead bearing circle, (2) no burst or shearburst located at the intersection of two wrenching flats reducesthe width across corners below its specified minimum, and (3)no burst or shear bu
24、rst has a width or depth greater than .06Dbut not to exceed .062 in. (1.6 mm).5.4.2 For flange bolts and screws and products with circularheads, bursts and shear bursts at the periphery of the flange orhead are permitted, provided that: (1) not more than one burstor shear burst has a width greater t
25、han 0.04 Dc , and (2) thewidth of the one burst or shear burst that exceeds a width of0.04 Dc does not have a width greater than 0.08 Dc.5.4.3 For indented head bolts and screws, bursts and shearbursts in the raised periphery of the indented head arepermitted, provided that: (1) no burst or shear bu
26、rst has a widthgreater than 0.06 D, and (2) no burst or shear burst has a depthextending below the indented portion.NOTE 2Bursts and shear bursts within the limits of this specificationmay be unsightly, but do not affect the mechanical properties or functionalrequirements of the bolt.5.5 Seams:5.5.1
27、 Seams in the shanks of bolts, screws, and studs arepermitted provided that no seam has a depth greater than 0.03D.5.5.2 Seams extending into the heads and flanges of boltsFIG. 1 Typical Quench CracksFIG. 2 Typical Forging CracksF 788/F 788M 082and screws are permitted, provided that they do not ope
28、nbeyond the limits specified for bursts and shear bursts in 5.4.5.6 Folds:5.6.1 Folds located at interior corners that are at or belowthe underhead bearing surface, for example, at the junction ofhead to shank, are not permitted, except for cloverleaf foldsoccurring at the intersection of non-circul
29、ar shoulders withhead bearing face (see Fig. 5a).5.6.2 Folds located at interior corners that are above theunderhead bearing surface, for example, at the junction of theFIG. 3 Typical Bursts and Shear BurstsFIG. 4 Typical SeamsFIG. 5 Typical FoldsF 788/F 788M 083hex head with the top of flange of fl
30、ange bolts and screws, arepermitted (see Fig. 5b).5.6.3 Folds located at exterior corners are permitted (seeFig. 5c).5.7 Voids:5.7.1 Voids on the surfaces of bolts, screws, and studs arepermitted, provided that: (1) depth of voids does not exceed0.25 mm or 0.010 in. or 0.02 D, whichever is greater,
31、and (2)the combined area of all voids on the underhead bearingsurface of bolts and screws does not exceed 10 % of thespecified minimum bearing surface area.5.7.2 The method for determining the area of voids on thebearing surface shall be as agreed upon between the purchaserand the producer.5.8 Tool
32、Marks:5.8.1 Tool marks on the underhead bearing surface arepermitted, provided the surface roughness measurement doesnot exceed 3.2 m or 125 in., determined as the arithmeticaverage deviation from the mean surface.5.8.2 Tool marks on other surfaces of the product arepermitted.5.9 Nicks and GougesNic
33、ks, gouges, dents, and scrapesare permitted, provided that the functionability of the productis not impaired.6. Inspection and Evaluation6.1 Bolts, screws, and studs shall be inspected for surfacediscontinuities in accordance with the procedure in 6.2, 6.3,and 6.4.6.2 The purchaser shall specify in
34、the original inquiry andpurchase order the inspection sampling requirements that theproducer must satisfy to demonstrate the acceptability of bolts,screws, and studs with respect to surface discontinuities.6.3 In the absence of purchaser instructions (6.2), inspectionand evaluation shall be in accor
35、dance with 6.5.6.4 For referee purposes, unless other procedures have beenspecified by the purchaser (6.2), inspection and evaluation shallbe in accordance with 6.5.6.5 Inspection Procedure:6.5.1 Visual Inspection:6.5.1.1 A random sample shall be taken from the lot inaccordance with Guide F 1470 and
36、 examined visually (mag-netic particle or fluid penetrant are recommended) for thepresence of quench cracks, forging cracks, bursts, shear bursts,seams, folds, voids, tool marks, and nicks and gouges. Visualinspection can include the use of devices that provide up to,and including, 10-power magnific
37、ation.6.5.1.2 If, during this inspection, any products are foundwith quench cracks in any location or with folds at interiorcorners that are at or below the underhead bearing surface, thelot may be rejected by the purchaser.6.5.1.3 If, during this inspection, any products are foundwith any other sur
38、face discontinuity, each discontinuity shallbe measured, and if any is found that exceeds the allowabledimensional limits for that discontinuity as specified in Sec-tion5, the lot may be rejected by the purchaser.6.5.1.4 When a GO ring gage will not assemble the fullthread length of an externally th
39、readed fastener when torque isapplied by hand, the following procedure shall be used todetermine thread acceptability. Using an appropriately cali-brated torque measuring device and an appropriately calibratedGO ring gage (class 3A for inch and 6h for metric fasteners)either hold the ring gage or th
40、e bolt stationary and rotate theother the full length of the bolt thread. Record the maximumtorque observed. Nicks and gouges shall not interfere withhand assembly of initial thread engagement or impair productfunction. No lubricant shall be added to the bolt or gage forpurposes of conducting the te
41、st. The indicated maximumtorque value shall not exceed those in Table 1 that are derivedthe indicated formula.7. Keywords7.1 bolts; crack; discontinuities (surface); fold; screw (ma-chine, sems, tapping); seam; studs; thread lap; voidFIG. 6 Typical VoidsFIG. 7 Typical Tool MarksF 788/F 788M 084SUPPL
42、EMENTARY REQUIREMENTSOne or more of the following supplementary requirements shall apply only when specified by thepurchaser in the inquiry and order. Supplementary Requirements shall in no way negate anyrequirement of the specification itself.S1. Assemblies Subject to Severe Dynamic StressesS1.1 La
43、ps in Screw Threads:S1.1.1 Laps of any depth and any length which originatebelow (or originating above and extending below) a pointlocated at a distance equal to or less than 20 % of the threadheight, measured from the minor diameter, are not permitted.See 4.5 and the Fig. S1.1 and Fig. S1.2.S1.1.2
44、Surface discontinuities of threads caused by thethread rolling process, as in Fig. S1.2, shall be excluded fromthese requirements provided the discontinuities do not exceedthe depth of 0.5 % 3 nominal diameter and are essentiallyparallel to the adjacent thread contour and are not directedtoward the
45、screw or bolt axis.S1.2 Thread Lap Inspection:S1.2.1 Visual InspectionA random sample shall be se-lected from the lot in accordance with F 1470. The sampleselected shall be surface etched in a 50 % solution of HCl andH2O at approximately 180F (no more than 5 min of etch timeshould be employed as exc
46、essive etching may remove shallowthread laps). After etch, the samples shall be examined under a103 magnification for the presence of laps.S1.2.2 Microscopic ExaminationIf laps are present, one ofthe samples shall be sectioned longitudinally on the center lineof the bolt/screw and on a plane passing
47、 through the point atwhich any lap extends closest to the minor diameter of thethread. The section shall be etched for microscopic examina-tion in accordance with Test Method E 340. Acceptance shallbe based on the requirements of S1.1.TABLE 1 Bolt and Screw Thread Discontinuity Acceptance CriteriaIn
48、ch MetricNominal Thread Size Max Allowable Torque Nominal Thread Size Max Allowable TorqueSize d (in.) T (in. lb.) Size d mm T Nm#10 0.190 1.0 M5 5 0.1#12 0.216 1.5 M6 6 0.214 0.250 2.5 M8 8 0.5516 0.312 4.5 M10 10 1.038 0.375 7.5 M12 12 1.7716 0.438 12.0 M14 14 2.712 0.500 18.0 M16 16 4.1916 0.563
49、26.0 M18 18 5.858 0.625 35.5 M20 20 8.034 0.750 61.0 M22 22 10.678 0.870 97.0 M24 24 13.81 1.000 145.0 M30 30 27.0118 1.125 206.0 M33 33 36.0114 1.250 283.0 M36 36 46.6138 1.375 377.0 . . .112 1.500 489.0 . . .Formula T = 145d3Formula T = 0.001d3FIG. S1.1 Typical Thread LapsF 788/F 788M 085SUMMARY OF CHANGESCommittee F16 has identified the location of selected changes to this standard since the last issueF 788/F 788M-07 that may impact the use of this standard. (Approved Nov. 1, 2008.)(1) 6.5.1.4 was added. (2) Table 1 was added.Commit
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