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18-8 SS Flat Socket Cap Screw

Selected 18-8 Stainless Steel Finish Hex Nut1/2-13 X 3 F879 18-8 Stainless Steel Flat Socket Cap Screw
18-8 Stainless Steel Finish Hex Nut1/2-13 X 3 F879 18-8 Stainless Steel Flat Socket Cap Screw

ASTM F879 stainless flat socket head cap screws have a countersunk head with a flat top surface and hexagonal recess. The ASTM F879 specification covers the requirements for stainless steel hexagon flat countersunk head cap screws for use in applications requiring general corrosion resistance. Dimensional specifications are governed by ASME B18.3. Stainless flat socket head cap screws are commonly used in applications in which it is necessary to recess the head of the fastener flush with the surface. Stainless steel fasteners are commonly used in applications that require general atmospheric corrosion resistance, such as chemical and food processing equipment. Stainless steel has a higher corrosion resistance than carbon steel.

Products

Mechanical Properties

Austenitic Stainless Steel Per ASTM F879-15
Alloy
Condition CW		 Full-Size Product Tests (1) Machined Specimen Tests Core Hardness (2)
Tensile
Strength		 Extension (3) Tensile
Strength		 Yield
Strength		 Elongation Vickers Rockwell
ksi Min ksi ksi % Min
80 min 0.4D 80 min 40 min 25 150 min 50 HRA min
  1. 1. 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.
  2. 2. Core hardness is only required when full-size product testing cannot be accomplished.
  3. 3. D denotes nominal thread size.

Chemical Properties

Per ASTM F879-15
Material Carbon Manganese Phosphorus Sulfur Silicon Chromium Nickel Copper
% by weight % by weight % by weight % by weight % by weight % by weight % by weight % by weight
Alloy Group 1,
UNS S30400		 0.08 2.00 0.045 0.030 1.00 18.0 to 20.0 8.0 to 10.5 1.00
  1. Composition, % maximum except as shown.

Dimensional Specifications

Alloy Steel Flat Socket cap screw dimensions 
Per ASME B18.3-2012
Size Nominal UNC UNF D A G P H J T LT
Body Head Diameter Protrusion
Gage Diameter		 Protrusion Head
Height		 Hex Socket Size Key
Engagement		 Thread Length
Max Min Max Min Max Min Max Min   Fraction Decimal Min Min Max
#0 0.0600   80 0.0600 0.0568 0.1380 0.1170 0.0780 0.0770 0.0360 0.0260 0.0440 …. 0.0350 0.0250 0.5000 0.6200
#1 0.0730 64 72 0.0730 0.0695 0.1680 0.1430 0.1010 0.1000 0.0400 0.0280 0.0540 …. 0.0500 0.0310 0.6200 0.7700
#2 0.0860 56 64 0.0860 0.0822 0.1970 0.1630 0.1240 0.1230 0.0430 0.0310 0.0640 …. 0.0500 0.0380 0.6200 0.8000
#3 0.0990 48 56 0.0990 0.0949 0.2260 0.1930 0.1480 0.1470 0.0460 0.0330 0.0730 1/16 0.0620 0.0440 0.6200 0.8300
#4 0.1120 40 48 0.1120 0.1075 0.2550 0.2180 0.1720 0.1710 0.0490 0.0360 0.0890 1/16 0.0620 0.0550 0.7500 0.9900
#5 0.1250 40 44 0.1250 0.1202 0.2810 0.2400 0.1960 0.1950 0.0510 0.0370 0.0900 5/64 0.0780 0.0610 0.7500 1.0000
#6 0.1380 32 40 0.1380 0.1329 0.3070 0.2630 0.2200 0.2190 0.0520 0.0370 0.0970 5/64 0.0780 0.0660 0.7500 1.0500
#8 0.1640 32 36 0.1640 0.1585 0.3590 0.3110 0.2670 0.2660 0.0550 0.0390 0.1120 3/32 0.0940 0.0760 0.8750 1.1900
#10 0.1900 24 32 0.1900 0.1840 0.4110 0.3590 0.3130 0.3120 0.0580 0.0410 0.1270 1/8 0.1250 0.0870 0.8750 1.2700
#12 0.2120 24 28 0.2160 0.2095 0.4500 0.4100 0.3600 0.3590 0.0690 0.0420 0.1350 1/8 0.1250 0.0940 1.0000 1.3300
1/4 0.2500 20 28 0.2500 0.2435 0.5310 0.4800 0.4240 0.4230 0.0640 0.0430 0.1610 5/32 0.1560 0.1110 1.0000 1.5000
5/16 0.3125 18 24 0.3125 0.3053 0.6560 0.6000 0.5390 0.5380 0.0700 0.4700 0.1980 3/16 0.1880 0.1350 1.1250 1.7100
3/8 0.3750 16 24 0.3750 0.3678 0.7810 0.7200 0.6530 0.6520 0.0760 0.0500 0.2340 7/32 0.2190 0.1590 1.2500 1.9400
7/16 0.4375 14 20 0.4375 0.4294 0.8440 0.7810 0.6900 0.6890 0.0920 0.0630 0.2340 1/4 0.2500 0.1590 1.3750 2.1700
1/2 0.5000 13 20 0.5000 0.4919 0.9380 0.8720 0.7390 0.7380 0.1190 0.0870 0.2510 5/16 0.3120 0.1720 1.5000 2.3800
5/8 0.6250 11 18 0.6250 0.6163 1.1880 1.1120 0.9620 0.9610 0.1350 0.0960 0.3240 3/8 0.3750 0.2200 1.7500 2.8200
3/4 0.7500 10 16 0.7500 0.7406 1.4380 1.3550 1.1860 1.1850 0.1500 0.1050 0.9600 1/2 0.5000 0.2200 2.0000 3.2500
7/8 0.8750 9 14 0.8750 0.8647 1.6880 1.6040 1.4110 1.1410 0.1650 0.1180 0.4680 9/16 0.5620 0.2480 2.2500 3.6900
1 1.0000 8 14 1.0000 0.9886 1.9380 1.8410 1.6350 1.6340 0.1810 0.1300 0.5400 5/8 0.6250 0.2970 2.5000 4.1200
1 1/8 1.1250 7 12 1.1250 1.1086 2.1880 2.0790 1.8590 1.8580 0.1960 0.1400 0.6110 3/4 0.7500 0.3250 2.8100 4.6500
1 1/4 1.2500 7 12 1.2500 1.2336 2.4380 2.3160 2.0830 2.0820 0.2120 0.1500 0.6830 7/8 0.8750 0.3580 3.1200 5.0900
1 3/8 1.3750 7 12 1.3750 1.3568 2.6880 2.5530 2.3060 2.3050 0.2280 0.1620 0.7550 7/8 0.8750 0.4020 3.4400 5.6500
1 1/2 1.5000 6 12 1.5000 1.4818 2.9380 2.7910 2.5300 2.5290 0.2430 0.1730 0.8270 1 1.0000 0.4350 3.7500 6.0800
  1. All dimensions are in inches.

Governing Standards

ASTM F879 This specification covers the chemical and mechanical requirements for stainless steel inch hexagon socket button (SBHCS) and flat countersunk (SFHCS) head cap screws with nominal thread 0.060 through 0.625 in. intended for use in applications requiring general corrosion resistance.
ASME B18.3 Covers the complete general and dimensional data for various types of hexagon socket cap screws, shoulder screws, set screws, and hexagon keys recognized as an American National Standard.
ASME B1.1 UNC & UNF Class 2A Specifies the thread form, series, class, allowance, tolerance, and designation for unified screw threads.

Stainless Steel Flat Socket Cap Screw Head Marking
Stainless Steel Flat Socket Cap Screw requires no material marking