1、Designation: F788/F788M 08 F788 12Standard Specification forSurface Discontinuities of Bolts, Screws, and Studs, Inchand Metric Series1This standard is issued under the fixed designation F788/F788M;F788; the number immediately following the designation indicates theyear of original adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. 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 Thi
3、s specification establishes 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 sp
4、ecification covers metric 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
5、.1.2 When the engineering requirements of the application necessitate control of surface discontinuities on bolts, screws, orstuds, the purchaser shall specify conformance to ASTM Specification F788/F 788M, in the original inquiry and purchase order.1.2.1 When the engineering requirements of the app
6、lication necessitate that surface 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 specifi
7、cation for metric bolts, screws, 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
8、are to be regarded separately 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:2E3
9、40 Test Method for Macroetching 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 Info
10、rmation3.1 Orders for bolts, 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 Surfac
11、e Discontinuities (see Terminology F1789 for definitions not provided)4.1 Crack4.1.1 Quench CracksTypical quench cracks are shown in Fig. 1. Limits are specified in 5.2.4.1.2 Forging CracksTypical forging cracks are shown in Fig. 2. Limits are specified in 5.3.4.2 BurstTypical bursts are shown in Fi
12、g. 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 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
13、 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 specified in 5.5.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
14、, PA 19428-2959. United States14.4 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 VoidA void is a shallow pocket or hollow on the surface of a bolt or screw due to nonfilling of metal during forg
15、ing. Voidsare produced 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 p
16、roduced by the movement 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 manufact
17、ure, handling or transport.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 Dcde
18、signates flange diameter (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 pe
19、rmitted.5.3 Forging 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 ma
20、y be unsightly, but do not affect the mechanical properties or functional requirementsof the bolt.1 This specification is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.93 on Quality AssuranceProvisions for Fasteners.Current edition app
21、roved Nov. 1, 2008Oct. 1, 2012. Published November 2008November 2012. Originally approved in 1982. Last previous edition approved in 20072008as F788/F788M 07.F788/F788M 08. DOI: 10.1520/F0788_F0788M-08.10.1520/F0788-12.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact
22、 ASTM 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:/www.ansi.org.FIG. 1 Typ
23、ical Quench CracksFIG. 2 Typical Forging CracksF788 1225.4 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 burst in the flatsextends into the crown (chamfer) circle on the top of the head or into th
24、e 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 or depth greater than .06D but not to exceed .062 in. (1.6 mm).FIG. 3 Typical Bursts and
25、Shear BurstsFIG. 4 Typical SeamsFIG. 5 Typical FoldsF788 1235.4.2 For flange bolts and screws and products with circular heads, bursts and shear bursts at the periphery of the flange or headare permitted, provided that: (1) not more than one burst or shear burst has a width greater than 0.04 Dc, and
26、 (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 of the indented head are permitted,provided that: (1) no burst or shear burst has a width
27、 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 mechanical properties or functionalrequirements of the bolt.5.5 Seams:5.5.1 Seams in the
28、 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 not open beyond thelimits specified for bursts and shear bursts in 5.4.5.6 Folds:5.6.1 Fol
29、ds 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 non-circular shoulders with head bearingface (see Fig. 5a).5.6.2 Folds located at interior
30、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 corners are permitted (see Fig. 5c).5.7 Voids:5.7.1 Voids on the surfaces of bolts, screws
31、, 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 andscrews does not exceed 10 % of the specified minimum bearing surface area.5.7.2 The me
32、thod 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 1245.8 Tool Marks:5.8.1 Tool marks on the underhead bearing surface are permitted, provided the surface roughness measurement
33、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 scrapes are permitted, provided that the functionability of the product is notimpaired.6
34、. 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 inquiry and purchase order the inspection sampling requirements that theproducer must satisfy t
35、o 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 6.5.6.4 For referee purposes, unless other procedures have been specified by the purchaser (6.
36、2), inspection and evaluation shall bein 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 in accordance with Guide F1470 and examined visually (magnetic particleor fluid penetrant are recommended) for the presence of quench crac
37、ks, 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, during this inspection, any products are found with quench cracks in any location or w
38、ith 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 discontinuity, each discontinuity shall bemeasured, and if any is found that exceeds the allowab
39、le 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 fastener when torque is appliedby hand, the following procedure shall be used to determine thr
40、ead acceptability. Using an appropriately calibrated torquemeasuring device and an appropriately calibrated GO ring gage (class 3A for inch and 6h for metric fasteners) either hold the ringgage or the bolt stationary and rotate the other the full length of the bolt thread. Record the maximum torque
41、observed. Nicks andgouges shall not interfere with hand assembly of initial thread engagement or impair product function. No lubricant shall be addedto the bolt or gage for purposes of conducting the test. The indicated maximum torque value shall not exceed those in Table 1 thatare derived the indic
42、ated formula.7. Keywords7.1 bolts; crack; discontinuities (surface); fold; screw (machine, sems, tapping); seam; studs; thread lap; voidTABLE 1 Bolt and Screw Thread Discontinuity Acceptance CriteriaInch MetricNominal Thread Size Max Allowable Torque Nominal Thread Size Max Allowable TorqueSize d (i
43、n.) 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 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 14
44、5.0 M30 30 27.01 18 1.125 206.0 M33 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 = 0.001d3F788 125SUPPLEMENTARY REQUIREMENTSOne or more of the following supplementary requirements shall apply only when specified by thepurchaser in the inq
45、uiry and order. Supplementary Requirements shall in no way negate anyrequirement of the specification itself.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 lo
46、cated ata distance equal to or less than 20 % of the thread height, measured from the minor diameter, are not 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 pr
47、ovided the discontinuities do not exceed the depth of 0.5 % nominal diameter and are essentially parallel to theadjacent thread contour and are not directed toward the screw or bolt axis.S1.2 Thread Lap Inspection:S1.2.1 Visual InspectionA random sample shall be selected from the lot in accordance w
48、ith F1470. The sample selected shallbe surface etched in a 50 % solution of HCl and H2O at approximately 180F (no more than 5 min of etch time should be employedas excessive etching may remove shallow thread laps). After etch, the samples shall be examined under a 10 magnification forthe presence of
49、 laps.S1.2.2 Microscopic ExaminationIf laps are present, one of the samples shall be sectioned longitudinally on the center line ofthe bolt/screw and on a plane passing through the point at which any lap extends closest to the minor diameter of the thread. Thesection shall be etched for microscopic examination in accordance with Test Method E340. Acceptance shall be based on therequirements of S1.1.FIG. S1.1 Typical Thread LapsF788 126SUMMARY OF CHANGESCommittee F16 has identified the location of selected changes to this stan
