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Socket Head Cap Screw

Selected A574 Hex Socket Cap Screw Alloy BlackSocket Screws & Fasteners
A574 Hex Socket Cap Screw Alloy BlackSocket Screws & Fasteners

ASTM A574 socket head cap screws (also known as Allen head screws) have a cylindrical head with a flat chamfered top surface, knurled cylindrical sides and hexagonal recess. The ASTM A574 specification covers the complete requirement for quenched and tempered high strength alloy steel hexagon socket head cap screws. Dimensional specifications are governed by ASME B18.3. Socket Head Cap screws supply greater tensile strength than equivalent hex head cap screws, while requiring less surface area to counterbore.These fasteners are commonly used in applications in which it is necessary to recess the head of the fastener, as well as applications where space limits the size of the head, and the tool that drives the fastener. Thread lengths listed are minimum thread lengths, actual thread length may be longer.

Products

Chemical Properties

Per ASTM A574-13
Material Heat Analysis Product Analysis
Carbon Phosphorus Sulfur Alloying Elements Carbon Phosphorus Sulfur Alloying Elements
% by weight % by weight % by weight % by weight % by weight % by weight
Quenched and tempered alloy steel 0.33 min 0.035 max 0.040 max (1) 0.31 min 0.040 max 0.045 max (1)
  1. 1. One or more of the following alloying elements: chromium, nickel, molybdenum, or vanadium shall be present in sufficient quantity to ensure that the specified strength properties are met after oil quenching and tempering. As a guide for selecting material, an alloy steel should be capable of meeting the specified mechanical requirements if the “as oil quenched” core hardness one diameter from the point is equal to or exceeds 25 HRC + (55 × carbon content).

Governing Standards

ASTM A574 Covers the requirements for quenched and tempered alloy steel hexagon socket-head cap screws, 0.060 through 4 in. in diameter where high strength is required.
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.

Alloy Steel Socket Head Cap Screw Marking
Alloy Steel Socket Head Cap Screw requires no material marking

Dimensional Specifications

Alloy steel cap screw dimensions
Per ASME B18.3-2012
Size Nominal UNC UNF D A H J LT
Body Diameter Head Diameter Head Height Hex Socket Size Thread
Length
Max Min Max Min Max Min Fraction
Nominal		 Decimal
Nominal		 Min
#0 0.0600   80 0.0600 0.0568 0.0960 0.0910 0.0600 0.0570 …. 0.0500 0.5000
#1 0.0730 64 72 0.0730 0.0695 0.1180 0.1120 0.0730 0.0700 1/16 0.0620 0.6625
#2 0.0860 56 64 0.0860 0.0822 0.1400 0.1340 0.0860 0.0830 5/64 0.0780 0.6250
#3 0.0990 48 56 0.0990 0.0949 0.1610 0.1540 0.0990 0.0950 5/64 0.0780 0.6250
#4 0.1120 40 48 0.1120 0.1075 0.1830 0.1760 0.1120 0.1080 3/32 0.0940 0.7500
#5 0.1250 40 44 0.1250 0.1202 0.2050 0.1980 0.1250 0.1210 3/32 0.0940 0.7500
#6 0.1380 32 40 0.1380 0.1329 0.2260 2.1800 0.1380 0.1340 7/64 0.1090 0.7500
#8 0.1640 32 36 0.1640 0.1585 0.2700 2.6200 0.1640 0.1590 9/64 0.1410 0.8750
#10 0.1900 24 32 0.1900 0.1840 0.3120 0.3030 0.1900 0.1850 5/32 0.1560 0.8750
#12 0.2120 24 28 0.2160 0.2095 0.3240 0.3140 0.2160 0.2100 5/32 0.1560 0.8750
1/4 0.2500 20 28 0.2500 0.2435 0.3750 0.3650 0.2500 0.2440 3/16 0.1880 1.0000
5/16 0.3125 18 24 0.3125 0.3053 0.4690 0.4570 0.3120 0.3060 1/4 0.2500 1.1250
3/8 0.3750 16 24 0.3750 0.3678 0.5620 0.5500 0.3750 0.3680 5/16 0.3120 1.2500
7/16 0.4375 14 20 0.4375 0.4294 0.6560 0.6420 0.4380 0.4300 3/8 0.3750 1.3750
1/2 0.5000 13 20 0.5000 0.4919 0.7500 0.7350 0.5000 0.4920 3/8 0.3750 1.5000
5/8 0.6250 11 18 0.6250 0.6163 0.9380 0.9210 0.6250 0.6160 1/2 0.5000 1.7500
3/4 0.7500 10 16 0.7500 0.7406 1.1250 1.1070 0.7500 0.7400 5/8 0.6250 2.0000
7/8 0.8750 9 14 0.8750 0.8647 1.3120 1.2930 0.8750 0.8640 3/4 0.7500 2.2500
1 1.0000 8 14 1.0000 0.9886 1.5000 1.4790 1.0000 0.9880 3/4 0.7500 2.5000
1 1/8 1.1250 7 12 1.1250 1.1086 1.6880 1.6650 1.1250 1.1110 7/8 0.8750 2.7500
1 1/4 1.2500 7 12 1.2500 1.2336 1.8750 1.8520 1.2500 1.2360 7/8 0.8750 3.0000
1 3/8 1.3750 7 12 1.3750 1.3568 2.0620 2.0380 1.3750 1.3600 1 1.0000 3.2500
1 1/2 1.5000 6 12 1.5000 1.4818 2.2500 2.2240 1.5000 1.4850 1 1.0000 3.5000
1 3/4 1.7500 5 12 1.7500 1.7295 2.6250 2.5970 1.7500 1.7340 1 1/4 1.2500 4.3800
2 2.0000 4 12 2.0000 1.9780 3.0000 2.9700 2.0000 1.9830 1 1/2 1.5000 5.0000
2 1/4 2.2500 4 12 2.2500 2.2280 3.3750 3.3440 2.2500 2.2320 1 3/4 1.7500 5.6200
2 1/2 2.5000 4 12 2.5000 2.4762 3.7500 3.7170 2.5000 2.4810 1 3/4 1.7500 6.2500
2 3/4 2.7500 4 12 2.7500 2.7262 4.1250 4.0900 2.7500 2.7300 2 2.0000 6.8800
3 3.0000 4 12 3.0000 2.9762 4.5000 4.4640 3.0000 3.9790 2 1/4 2.2500 7.5000
3 1/4 3.2500 4 12 3.2500 3.2262 4.8750 4.8300 3.2500 3.2280 2 1/4 2.2500 8.1200
3 1/2 3.5000 4 12 3.5000 3.4762 5.2500 5.2110 3.5000 3.4780 2 3/4 2.7500 8.7500
3 3/4 3.7500 4 12 3.7500 3.7262 5.6250 5.5840 3.7500 3.7270 2 3/4 2.7500 9.3800
4 4.0000 4 12 4.0000 3.9762 6.0000 5.9580 4.0000 3.9760 3 3.0000 10.0000
  1. All dimensions are in inches.

Mechanical Properties

Alloy Steel, Quenched & Tempered Per ASTM A574-13
Nominal
Diameter		 Full-Size Screws Product
Hardness		 Machined Test Specimen
Tensile
Strength		 Proof
Load		 Yield Strength
at 0.2% offset		 Tensile
Strength		 Elongation
in 5D		 Reduction
of Area
ksi ksi Rockwell ksi ksi % %
1/2" & under 180 min 140 39-45 HRC 153 min 180 min 10 min 35 min
over 1/2" 170 min 135 37-45 HRC 153 min 170 min 10 min 35 min