ASTM F879-23

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F879 − 15 (Reapproved 2020) F879 − 23
Standard Specification for
Stainless Steel Socket Button Button, Low and Flat
Countersunk Head Cap Screws
This standard is issued under the fixed designation F879; the number immediately following the designation indicates the year of original
adoption or, in the case of 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 U.S. Department of Defense.
1. Scope*
1.1 This specification covers the chemical and mechanical requirements for stainless steel inch hexagon socket button (SBHCS)
and (SBHCS), flat countersunk (SFHCS) head cap screws with nominal thread 0.060 through 0.625 in. and low head (SLHCS)
cap screws with nominal thread 0.112 through 0.625 in. intended for use in applications requiring general corrosion resistance.
1.2 Two groups of austenitic stainless steel alloys and three conditions are covered. See Table 1 and Table 2.
1.3 Units—The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in
this standard.
1.4 The following precautionary caveat pertains only to the test method portion, Section 12, of this specification: This standard
does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this
standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory
limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A262 Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
A342/A342M Test Methods for Permeability of Weakly Magnetic Materials
A380/A380M Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems
A555/A555M Specification for General Requirements for Stainless Steel Wire and Wire Rods
A751 Test Methods and Practices for Chemical Analysis of Steel Products
A967/A967M Specification for Chemical Passivation Treatments for Stainless Steel Parts
D3951 Practice for Commercial Packaging
E18 Test Methods for Rockwell Hardness of Metallic Materials
E92 Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials
E384 Test Method for Microindentation Hardness of Materials
This specification is under the jurisdiction of ASTM Committee F16 on Fasteners and is the direct responsibility of Subcommittee F16.04 on Nonferrous Fasteners.
Current edition approved April 1, 2020June 1, 2023. Published April 2020July 2023. Originally approved in 1986. Last previous edition approved in 20152020 as
F879F879 – 15 (2020).-15. DOI: 10.1520/F0879-15R20.10.1520/F0879-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
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F879 − 23
TABLE 1 Mechanical Property Requirements
A B
Full Size Product Tests Machined Specimen Tests Core Hardness
Alloy
C
Alloy Group
Tensile Extension Tensile Yield Elongation
Condition Vickers Rockwell
min
Strength ksi Strength ksi Strength ksi % min
All AF 85 max 0.6D 85 max 55 max 40 210 max 95 HRB max
All CW 80 min 0.4D 80 min 40 min 25 150 min 50 HRA min
All CW1 102 min 0.4D 87 min 65 min 20 220 min 59 HRA min
A
Actual full-size testing of condition CW and CW1 may result in decreased tensile strength because of the head configuration (see Table 3). For fasteners with nominal
thread diameters larger than 0.625 in., the mechanical properties shall be agreed upon between the user and manufacturer.
B
Core hardness is only required when full-size product testing cannot be accomplished.
C
D denotes nominal thread size.
TABLE 2 Chemical Requirements
Composition, % maximum except as shown
Alloy UNS Manganese
Alloy Carbon Phosphorus Sulfur Silicon Chromium Nickel Copper Molybdenum
Group Designation
Austenitic Alloys
1 S30400 304 0.08 2.00 0.045 0.030 1.00 18.0 to 8.0 to 1.00 . . .
20.0 10.5
1 S30403 304L 0.030 2.00 0.045 0.030 1.00 18.0 to 8.0 to 1.00 . . .
20.0 12.0
1 S30500 305 0.12 2.00 0.045 0.030 1.00 17.0 to 10.5 to 1.00 . . .
19.0 13.0
1 S38400 384 0.08 2.00 0.045 0.030 1.00 15.0 to 17.0 to . . . . . .
17.0 19.0
1 S30430 18–9LW 0.10 2.00 0.045 0.030 1.00 17.0 to 8.0 to 3.0 to 4.0 . . .
19.0 10.0
1 S30433 302HQ 0.03 2.00 0.045 0.030 1.00 17.0 to 8.0 to 3.0 to 4.0 . . .
19.0 10.0
A
1 . 304J3 0.08 2.00 0.045 0.030 1.00 17.0 to 8.0 to 1.00 to . . .
19.0 10.5 3.00
2 S31600 316 0.08 2.00 0.045 0.030 1.00 16.0 to 10.0 to . . . 2.00 to 3.0
18.0 14.0
2 S31603 316L 0.03 2.00 0.045 0.030 1.00 16.0 to 10.0 to . . . 2.00 to 3.0
18.0 14.0
A
304J3 from JIS G 4309.
F593 Specification for Stainless Steel Bolts, Hex Cap Screws, and Studs
F606/F606M Test Methods for Determining the Mechanical Properties of Externally and Internally Threaded Fasteners,
Washers, Direct Tension Indicators, and Rivets
F788 Specification for Surface Discontinuities of Bolts, Screws, Studs, and Rivets, Inch and Metric Series
F1470 Practice for Fastener Sampling for Specified Mechanical Properties and Performance Inspection
2.2 ASME Standard:
B 18.3 Socket Cap, Shoulder and Set Screws (Inch Series)
2.3 JIS Standard:
JIS G 4309 Stainless Steel Wires
3. Classification
3.1 The designation of the alloy group and condition of this specification shall be consistent with the stainless steel designations
in Specification F593.
3.2 Screws shall be designated by group and condition (for example, F879 Group 1 Condition AF).
4. Ordering Information
4.1 Orders for material under this specification shall include the following information:
4.1.1 Quantity (number of pieces of each item).
Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
www.asme.org.
Available from Japanese Industrial Standards Committee (JIS) 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo 100-8901, JAPAN. http://www.jisc.go.jp
F879 − 23
4.1.2 Name of the screw, SBHCS SBHCS, SLHCS or SFHCS.
4.1.3 Dimensions, including nominal thread designation, thread pitch, and nominal screw length (inches). A standard part number
may be used for this definition.
4.1.4 Alloy group and condition.
4.1.5 Certification, if required (see Section 15).
4.1.6 ASTM specification and year of issue.
4.1.7 Any special or supplemental requirements (see Supplementary Requirements S1 through S6).S7).
5. Materials and Manufacture
5.1 Screws shall be formed by upsetting or extruding, or both.
5.2 Screws shall be roll threaded.
5.3 Heat Treatment—Austenitic alloys Condition AF screws, following manufacture, shall be annealed by heating to 1900 6 50 °F
to obtain maximum corrosion resistance and minimum permeability. The screws shall be held for a sufficient time at temperature,
then cooled at a rate sufficient to prevent precipitation of the carbide and provide the properties specified in Table 1.
5.4 When Condition CW or CW1 is specified, the austenitic alloys shall be annealed as specified in 5.3, generally by the raw
material manufacturer, then cold worked to develop specific properties.
6. Chemical Composition
6.1 The chemical composition of the screws shall conform to the requirements of Table 2.
6.2 Unless otherwise specified in the inquiry and purchase order (see Supplementary Requirement S2), the choice of an alloy from
within a group shall be that of the fastener manufacturer as determined by his fabrication methods and material availability. The
specific alloy from within a group used by the manufacturer shall be clearly identified on all certification required in the purchase
order.
6.3 When chemical analysis is performed by the purchaser using finished fasteners, the chemical composition obtained shall
conform to the limits specified in Table 2 for the specific alloy. Chemical composition shall conform to the tolerances specified
in Specification A555/A555M.
6.3.1 In the event of a discrepancy, a referee analysis of the samples for each lot as specified in 12.1 shall be made in accordance
with 11.3.1.
7. Mechanical Properties
7.1 The finished screws shall conform to the mechanical requirements specified in Table 1.
7.2 Screws having a nominal length equal to or greater than three diameters shall be tensile tested full size and shall meet the full
size breaking strength requirements specified in Table 3. Tensile failures through the head are acceptable providing the load
requirements are satisfied.
7.3 Screws that are too short (lengths less than specified in 7.2 or that have insufficient threads for tension testing) shall not be
subject to tension tests, but shall conform to the hardness requirements of Table 1.
F879 − 23
TABLE 3 Breaking Strength Values for Full Size Fasteners
NOTE 1—Breaking loads are based on tensile stress area and strengths
of 85 ksi max (AF), 64 ksi min (CW), and 82 ksi for CW1. The minimum
loads for the CW and CW1 conditions are based on the tensile properties
of 80 ksi minimum material strength and 102 ksi minimum material
strength, respectively, reduced by 20 % to allow for the head critical
nature of these configurations. See Note A in Table 1. Actual strength of
the threaded section, if size permits, may be determined by removing the
head and testing the threaded section as a stud.
Alloy Condition, lb. min
Tensile Stress
Nominal Size
Area, in.
AF CW CW1
0 0.060–80 0.00180 153 115 147
1 0.073–64 0.00263 223 168 215
2 0.086–56 0.00370 314 237 303
3 0.099–48 0.00487 414 312 399
4 0.112–40 0.00604 513 386 495
5 0.125–40 0.00796 676 509 652
6 0.138–32 0.00909 772 581 745
8 0.164–32 0.0140 1191 897 1149
10 0.190–24 0.0175 1490 1122 1438
⁄4 0.250–20 0.0318 2705 2037 2609
⁄16 0.312–18 0.0524 4457 3356 4299
⁄8 0.375–16 0.0775 6587 4959 6354
⁄2 0.500–13 0.1419 12 061 9082 11 636
⁄8 0.625–11 0.226 19 210 14 464 18 532
8. Corrosion Resistance Requirements
8.1 Carbide Precipitation:
8.1.1 Rod, bar, and wire used to make fasteners in accordance with this specification shall be capable of passing the test for
susceptibility to intergranular corrosion as specified in Practice E of Practices A262.
8.1.2 As stated in Practices A262, samples may be subjected to the faster and more severe screening test in accordance with
Practice A. Failing Practice A, specimens shall be tested to Practice E and be considered satisfactory if passing Practice E.
9. Dimensions
9.1 Unless otherwise specified, the dimensions shall conform to the requirements of ASME B18.3.
10. Workmanship and Finish
10.1 Surface Treatment—Unless otherwise specified, screws shall be cleaned, descaled, and passivated in accordance with Practice
A380/A380M or Specification A967/A967M at the option of the manufacturer.
10.2 Surface Discontinuities:
10.2.1 The surface discontinuities for these products shall conform to Specification F788 and the additional limitations specified
herein.
10.2.1.1 Forging defects that connect the socket to the periphery of the head are not permissible. Defects originating on the
periphery and with a traverse indicating a potential to intersect are not permissible. Other forging defects are permissible provided
those located in the bearing area, fillet, and top surfaces shall not have a depth exceeding 0.03 D or 0.005 in. whichever is greater.
For peripheral discontinuities, the maximum depth may be 0.06 D (see Fig. 1).
10.2.1.2 Forging defects located in the socket wall within 0.1 times the actual key engagement, T, from the bottom of the socket
are not permissible. Discontinuities located elsewhere in the socket shall not have a length exceeding 0.25 T, or a maximum depth
of 0.03 D not to exceed 0.005 in. (see Fig. 2).
10.2.1.3 Seams in the shank shall not exceed a depth of 0.03 D or 0.008 in. whichever is greater.
F879 − 23
FIG. 1 Head Discontinuities (See 10.2.1)
FIG. 2 Socket Discontinuities (See 10.2.1)
10.2.1.4 No transverse discontinuities shall be permitted in the head-to-shank fillet area.
10.2.1.5 Threads shall have no laps at the root or on the flanks, as shown in Fig. 3. Laps are permitted at the crests (Fig. 3(C))
that do not exceed 25 % of the basic thread depth, and on the flanks outside the pitch cylinder. Longitudinal seams rolled beneath
the root of the thread and across the crests of the threads are acceptable within the limits of 10.2.1.3.
11. Numbe
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