ASTM F879 Specification

Scope

This specification outlines the chemical and mechanical requirements for stainless steel inch-series socket button head cap screws (SBHCS) and flat countersunk head cap screws (SFHCS), with nominal thread diameters ranging from 0.060 to 0.625 inches. These fasteners are intended for general industrial use where high strength and corrosion resistance are required.

ASTM F879M serves as the metric counterpart to ASTM F879, covering SBHCS and SFHCS in sizes from M1.6 to M16. The standard includes three property conditions for austenitic alloys:

  • Group 1 in annealed condition (AF) at a maximum of 85 ksi

  • Cold worked condition (CW) with a minimum of 80 ksi

  • Cold worked condition 1 (CW1) with a minimum of 102 ksi

At Adfast Components, we manufacture socket button head and flat countersunk head screws in full compliance with both ASTM F879 and F879M specifications. All products are tested and supplied with EN 10204 Type 3.1 certification. Commonly offered materials include stainless steel grades 304, 304L, 316, and 316L, with other grades available upon request.

Chemical Composition

Composition, & maximum except as shown
UNS DesignationAlloyCarbonManganesePhosphorusSulfurSiliconChromiumNickelCopperMolybdenum
Austenitic Alloys
S304003040.082.000.0450.03118.0 – 20.08.0 – 10.51.00
A30403304L0.032.000.0450.030118.0 – 20.08.0 – 12.01.00
S305003050.122.000.0450.03117.0 – 19.010.5 – 13.01.00
S384003840.082.000.0450.030115.0 – 17.017.0 – 19.0
S3043018-9LW0.102.000.0450.030117.0 – 19.08.0 – 10.03.0 – 4.0
S30433302HQ0.032.000.0450.030117.0 – 19.08.0 – 10.03.0 – 4.0
S316003160.082.000.0450.030116.0 – 18.010.0 – 14.02.0 – 3.0
S31603316 L0.032.000.0450.030116.0 – 18.010.0 – 14.02.0 – 3.0

Mechanical Properties

ConditionFull Size ProductAMachined SpecimenCore HardnessB
Tensile Strength, ksiMinimum ExtensionCTensile Strength, ksiYield Strength, ksiMinimum Elongation, %VickersRockwell
AF85 max0.6D85 max55 max40210 max95 HRB max
CW80 min0.4D80 min40 min25150 min50 HRA min
CW1102 min0.4D87 min65 min20220 min59 HRA min

A Actual full size testing of condition CW and CW1 may result in decreased tensile strength because of the head configuration. For fasteners with nominal thread diameters larger than 0.625 inch, the mechanical properties shall be agreed upon between the user and the manufacturer.
B Core hardness is only required when full size product tensile testing cannot be accomplished.
C D denoted nominal thread size.

Tensile Strength Values for Full Size Fasteners, lbs

Nominal SizeStress AreaAlloy Group 1, lbs, min
AFCWCW1
00.060-800.0018153115147
10.073-640.00263223168215
20.086-560.00370314237303
30.099-480.00487414312399
40.112-480.00604513386495
50.125-400.00796676509652
60.138-320.00909772581745
80.164-320.0140011918971149
100.190-240.01750149011221438
1/4″0.250-200.03180270520372609
5/16″0.312-180.05240445733564299
3/8″0.375-160.077506 58749596354
1/2″0.500-130.1419012061908211636
5/8″0.625-110.22600192101446418532