1、Designation: F788 12F788 13Standard Specification forSurface Discontinuities of Bolts, Screws, and Studs, Inchand Metric Series1This standard is issued under the fixed designation F788; the number immediately following the designation indicates the year of originaladoption or, in the case of revisio
2、n, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () 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 specification establ
3、ishes allowable limits for the various types of surface discontinuities that may occur during themanufacture and processing of bolts, screws, and studs, including heat-treated machine screws, tapping screws, and sems (thewashers of screw-washer assemblies are excluded). This specification covers met
4、ric series products with nominal diameters of 4mm and larger and with specified minimum tensile strengths of 420 MPa and higher; and inch series products with nominaldiameters of No. 5 (0.1250 in.) and larger and with specified minimum tensile strengths of 60 000 psi and higher.1.2 When the engineer
5、ing requirements of the application necessitate control of surface discontinuities on bolts, screws, orstuds, the purchaser shall specify conformance to ASTM Specification F788, in the original inquiry and purchase order.1.2.1 When the engineering requirements of the application necessitate that sur
6、face discontinuities on bolts, screws, and studsbe controlled within limits closer than those specified in this specification, the purchaser shall specify the applicable limits in theoriginal inquiry and purchase order.1.3 The allowable limits established in this specification for metric bolts, scre
7、ws, and studs with nominal diameters from 4 to24 mm inclusive, are essentially identical with requirements given 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 units are to be regarded separately
8、 as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from thetwo systems may result in non-conformance with the standard.2. Referenced Documents2.1 ASTM Standards:2E340 Test Method for Macroetchi
9、ng Metals and AlloysF1470 Practice for Fastener Sampling for Specified Mechanical Properties and Performance InspectionF1789 Terminology for F16 Mechanical Fasteners2.2 ISO Standard:3ISO 6157/I Fasteners, Surface Discontinuities on Bolts, Screws and Studs3. Ordering Information3.1 Orders for bolts,
10、screws, and studs requiring discontinuity control shall include the following:3.1.1 ASTM designation and date of issue of this specification.3.1.2 Special requirements, for example, closer discontinuity limits (1.2.1) and inspection sampling plan (6.2).4. Types of Surface Discontinuities (see Termin
11、ology F1789 for definitions not provided)4.1 Crack4.1.1 Quench CracksTypical quench cracks are shown in Fig. 1. Limits are specified in 5.2.1 This specification is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.93 on Quality AssurancePr
12、ovisions for Fasteners.Current edition approved Oct. 1, 2012April 1, 2013. Published November 2012April 2013. Originally approved in 1982. Last previous edition approved in 20082012 asF788/F788M 08.F788 12. DOI: 10.1520/F0788-12.10.1520/F0788-13.2 For referencedASTM standards, visit theASTM website,
13、 www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:
14、/www.ansi.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users con
15、sult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
16、, PA 19428-2959. United States14.1.2 Forging CracksTypical forging cracks are shown in Fig. 2. Limits are specified in 5.3.4.2 BurstTypical bursts are shown in Fig. 3. Limits are specified in 5.4.4.2.1 Shear BurstA shear burst is an open break in the metal located at approximately a 45 angle to the
17、product axis. Shearbursts occur most frequently at the periphery of products having flanged or circular heads. Shear bursts may also occur on the sidesof hex-head products. Typical shear bursts are shown in Fig. 3. Limits are specified in 5.4.4.3 SeamTypical seams are shown in Fig. 4. Limits are spe
18、cified 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 Supplementary Requirement S.1.1.4.6 VoidAvoid is a shallow pocket or hollow on the surface of a bolt or screw due to nonfilling of metal during forging. Voidsare prod
19、uced by marks or impressions of chips (shear burrs) or by rust formation on the raw material.They are not planished duringforging. Typical voids are shown in Fig. 6. Limits are specified in 5.7.4.7 Tool MarksTool marks are longitudinal or circumferential grooves of shallow depth produced by the move
20、ment ofmanufacturing tools over the surface of the bolt or screw. Typical tool marks are shown in Fig. 7. Limits are specified in 5.8.4.8 Gouge and Nickan indentation on the surface of a fastener produced by impact with another fastener, or from processingequipment during manufacture, handling or tr
21、ansport.5. Allowable Limits5.1 Letter DefinitionsThroughout the following requirements, D designates the nominal size (basic major diameter of thread)of bolts, screws, and studs, except for products with shoulders, in which case D designates the largest shoulder diameter; and Dcdesignates flange dia
22、meter (specified maximum) or head diameter (specified maximum) of circular head products. For metric seriesproducts, D and Dc are in millimetres; for inch-series products, D and Dc are in inches.5.2 Quench CracksQuench cracks of any depth, any length, or in any location are not permitted.5.3 Forging
23、 CracksForging cracks on the top of the head of bolts and screws are permitted, provided that (a) no crack shallhave a length exceeding 1.0 D, and ( b) no crack shall have a width or depth exceeding 0.04 D. See Note 1.NOTE 1Forging cracks within the limits of this specification may be unsightly, but
24、 do not affect the mechanical properties or functional requirementsof the bolt.FIG. 1 Typical Quench CracksFIG. 2 Typical Forging CracksF788 1325.4 Bursts and Shear Bursts (see Note 2):5.4.1 For hex-head bolts and screws, bursts and shear bursts are permitted, provided that: (1) no burst or shear bu
25、rst in the flatsextends into the crown (chamfer) circle on the top of the head or into the underhead bearing circle, (2) no burst or shear burstlocated at the intersection of two wrenching flats reduces the width across corners below its specified minimum, and (3) no burstor shear burst has a width
26、or depth greater than .06D but not to exceed .062 in. (1.6 mm).FIG. 3 Typical Bursts and Shear BurstsFIG. 4 Typical SeamsFIG. 5 Typical FoldsF788 1335.4.2 For flange bolts and screws and products with circular heads, bursts and shear bursts at the periphery of the flange or headare permitted, provid
27、ed that: (1) not more than one burst or shear burst has a width greater than 0.04 Dc, and (2) the width of theone burst or shear burst that exceeds a width of 0.04 Dc does not have a width greater than 0.08 Dc.5.4.3 For indented head bolts and screws, bursts and shear bursts in the raised periphery
28、of the indented head are permitted,provided that: (1) no burst or shear burst has a width greater than 0.06 D, and (2) no burst or shear burst has a depth extendingbelow the indented portion.NOTE 2Bursts and shear bursts within the limits of this specification may be unsightly, but do not affect the
29、 mechanical properties or functionalrequirements of the bolt.5.5 Seams:5.5.1 Seams in the shanks of bolts, screws, and studs are permitted provided that no seam has a depth greater than 0.03 D.5.5.2 Seams extending into the heads and flanges of bolts and screws are permitted, provided that they do n
30、ot open beyond thelimits specified for bursts and shear bursts in 5.4.5.6 Folds:5.6.1 Folds located at interior corners that are at or below the underhead bearing surface, for example, at the junction of headto shank, are not permitted, except for cloverleaf folds occurring at the intersection of no
31、n-circular shoulders with head bearingface (see Fig. 5a).5.6.2 Folds located at interior corners that are above the underhead bearing surface, for example, at the junction of the hex headwith the top of flange of flange bolts and screws, are permitted (see Fig. 5 b).5.6.3 Folds located at exterior c
32、orners are permitted (see Fig. 5c).5.7 Voids:5.7.1 Voids on the surfaces of bolts, screws, and studs are permitted, provided that: (1) depth of voids does not exceed 0.25 mmor 0.010 in. or 0.02 D, whichever is greater, and (2) the combined area of all voids on the underhead bearing surface of bolts
33、andscrews does not exceed 10 % of the specified minimum bearing surface area.5.7.2 The method for determining the area of voids on the bearing surface shall be as agreed upon between the purchaser andthe producer.FIG. 6 Typical VoidsFIG. 7 Typical Tool MarksF788 1345.8 Tool Marks:5.8.1 Tool marks on
34、 the underhead bearing surface are permitted, provided the surface roughness measurement does not exceed3.2 m or 125 in., determined as the arithmetic average deviation from the mean surface.5.8.2 Tool marks on other surfaces of the product are permitted.5.9 Nicks and GougesNicks, gouges, dents, and
35、 scrapes are permitted, provided that the functionability of the product is notimpaired.6. Inspection and Evaluation6.1 Bolts, screws, and studs shall be inspected for surface discontinuities in accordance with the procedure in 6.2, 6.3, and 6.4.6.2 The purchaser shall specify in the original inquir
36、y and purchase 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), inspection and evaluation shall be in accordance with 6.5.6
37、.4 For referee purposes, unless other procedures have been specified by the purchaser (6.2), inspection and evaluation shall bein accordance with 6.5.6.5 Inspection Procedure:6.5.1 Visual Inspection:6.5.1.1 Arandom sample shall be taken from the lot in accordance with Guide F1470 and examined visual
38、ly (magnetic particleor fluid penetrant are recommended) for the presence of quench cracks, forging cracks, bursts, shear bursts, seams, folds, voids,tool marks, and nicks and gouges. Visual inspection can include the use of devices that provide up to, and including, 10-powermagnification.6.5.1.2 If
39、, during this inspection, any products are found with quench cracks in any location or with folds at interior corners thatare at or below the underhead bearing surface, the lot may be rejected by the purchaser.6.5.1.3 If, during this inspection, any products are found with any other surface disconti
40、nuity, each discontinuity shall bemeasured, and if any is found that exceeds the allowable dimensional limits for that discontinuity as specified in Section5, the lotmay be rejected by the purchaser.6.5.1.4 When a GO ring gage will not assemble the full thread length of an externally threaded fasten
41、er when torque is appliedby hand, whether due to surface discontinuities or coating buildup, or both, the following procedure shall be used to determinethread acceptability. Using an appropriately calibrated torque measuring device and an appropriately calibrated GO ring gage (class3A for inch and 6
42、h for metric fasteners) either hold the ring gage or the bolt stationary and rotate the other the full length of thebolt thread. Record the maximum torque observed. Nicks and gouges Nicks, gouges, or accumulation of coating materials shallnot interfere with hand assembly of initial thread engagement
43、 or impair product function. No lubricant shall be added to the boltor gage for purposes of conducting the test. The indicated maximum torque value shall not exceed those in Table 1 that are derivedthe indicated formula.7. Keywords7.1 bolts; crack; discontinuities (surface); fold; screw (machine, se
44、ms, tapping); seam; studs; thread lap; voidF788 135SUPPLEMENTARY 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.
45、S1. Assemblies Subject to Severe Dynamic StressesS1.1 Laps in Screw Threads:S1.1.1 Laps of any depth and any length which originate below (or originating above and extending below) a point located ata distance equal to or less than 20 % of the thread height, measured from the minor diameter, are not
46、 permitted. See 4.5 and theFig. S1.1 and Fig. S1.2.S1.1.2 Surface discontinuities of threads caused by the thread rolling process, as in Fig. S1.2, shall be excluded from theserequirements provided the discontinuities do not exceed the depth of 0.5 % nominal diameter and are essentially parallel to
47、theadjacent thread contour and are not directed toward the screw or bolt axis.S1.2 Thread Lap Inspection:TABLE 1 Bolt and Screw Thread Discontinuity Acceptance CriteriaInch MetricNominal Thread Size Max AllowableTorqueNominal Thread Size Max AllowableTorqueSize d (in.) T (in. lb.) Size d mm T Nm#10
48、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 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 27.01 18 1.125 206.0 M3
49、3 33 36.01 14 1.250 283.0 M36 36 46.61 38 1.375 377.0 . . .1 12 1.500 489.0 . . .Formula T = 145d3 Formula T = 0.001d3TABLE 1 Bolt and Screw Thread Discontinuity Acceptance CriteriaInch Fasteners Metric FastenersSizeNominalDiameter (d)in.AllowableTorque SizeNominalDiameter (d)mmAllowableTorquein. lb ft. lb 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 1.0 M14 14 2.712 0.500 1.5 M16 16 4.1916 0.563 2.2 M18 18 5.858 0.625 3.0 M20 20 8.034 0.750 5.1
