ANSI/ASME B18.3 Hexagon Socket Button Head Cap Screws
ANSI/ASME B18.3 Hexagon Socket Button Head Cap Screws feature a rounded, low-profile head and internal hexagon socket drive, offering a compact fastening solution for applications where a reduced head height and clean appearance are preferred. The socket drive provides convenient top-side access for tightening, while the rounded button head offers a smooth profile and a defined bearing surface.
These screws are available in alloy steel and stainless steel to meet different mechanical and environmental requirements. Alloy steel versions can be supplied to the applicable ASTM F835 requirements, while stainless steel versions can be specified to ASTM F879. Different inch sizes, thread configurations, finishes, and material options allow the fastener to be selected according to the load, available space, and service environment. They are commonly used in machinery, equipment, fixtures, guards, panels, and compact mechanical assemblies, particularly where a conventional socket head cap screw would provide more head height than necessary.
Specification:
ANSI/ASME B18.3 specifies the dimensional requirements for Hexagon Socket Button Head Cap Screws, including the button head geometry, socket dimensions, screw sizes, and other applicable dimensions. The Unified inch threads are manufactured in accordance with the applicable requirements of ASME B1.1. Mechanical requirements depend on the selected material: alloy steel versions are specified to ASTM F835, while stainless steel versions are specified to ASTM F879.
| Item | Specification |
|---|---|
| Standard | ANSI/ASME B18.3 |
| Product Type | Hexgaon Socket Button Head Cap Screw |
| Head Style | Button Head |
| Drive Type | Hexagon Socket |
| Thread System | Unified Inch |
| Thread Series | UNC/UNF |
| Thread Standard | ASME B1.1 |
| Size Range | #0-3/4" |
| Alloy Standard | ASTM F835 |
| Stainless Steel Standard | ASTM F879 |
| Material | Carbon Steel,Alloy Steel,Stainless Steel |
| Surface Treatment | Zinc Plated,Black Oxidation,Dacromet,Bright Finish,Passivation |
Dimension Chart of ANSI/ASME B18.3 Hexagon Socket Button Head Cap Screws:
| Thread Diameter | #0 | #1 | #2 | #3 | #4 | #5 | #6 | #8 | #10 | 1/4 | 5/16 | 3/8 | 7/16 | 1/2 | 5/8 | 3/4 |
| P | 80 | 64 | 56 | 48 | 40 | 40 | 32 | 32 | 24 | 20 | 18 | 16 | 14 | 13 | 11 | 10 |
| dk max | 0.114 | 0.139 | 0.164 | 0.188 | 0.213 | 0.238 | 0.262 | 0.312 | 0.361 | 0.437 | 0.547 | 0.656 | 0.765 | 0.875 | 1 | 1.125 |
| dk min | 0.104 | 0.129 | 0.154 | 0.176 | 0.201 | 0.226 | 0.25 | 0.298 | 0.347 | 0.419 | 0.527 | 0.636 | 0.746 | 0.851 | 0.97 | 1.105 |
| k max | 0.032 | 0.039 | 0.046 | 0.052 | 0.059 | 0.066 | 0.073 | 0.087 | 0.101 | 0.132 | 0.166 | 0.199 | 0.231 | 0.265 | 0.331 | 0.375 |
| k min | 0.026 | 0.033 | 0.038 | 0.044 | 0.051 | 0.058 | 0.063 | 0.077 | 0.091 | 0.122 | 0.152 | 0.185 | 0.218 | 0.245 | 0.311 | 0.355 |
| t min | 0.02 | 0.028 | 0.028 | 0.035 | 0.035 | 0.044 | 0.044 | 0.052 | 0.07 | 0.087 | 0.105 | 0.122 | 0.14 | 0.175 | 0.21 | 0.245 |
| s max | 0.0355 | 0.051 | 0.051 | 0.0635 | 0.0635 | 0.0791 | 0.0791 | 0.0952 | 0.127 | 0.1587 | 0.19 | 0.2217 | 0.253 | 0.316 | 0.379 | 0.442 |
| s min | 0.035 | 0.05 | 0.05 | 0.0625 | 0.0625 | 0.0781 | 0.0781 | 0.0937 | 0.125 | 0.1562 | 0.1875 | 0.2187 | 0.25 | 0.3125 | 0.375 | 0.4375 |
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Application of ANSI/ASME B18.3 Hexagon Socket Button Head Cap Screws:
Compact Machinery & Equipment
Hexagon Socket Button Head Cap Screws are suitable for machine components, equipment housings, covers, guards, and compact mechanical assemblies where a lower and rounded head profile helps reduce protrusion above the assembled surface. The hexagon socket also provides convenient access when tightening space around the fastener is limited.
Fixtures, Panels & Mounting Components
The button head design provides a smooth, rounded profile for fixtures, mounting plates, brackets, panels, and equipment components where a conventional high-profile socket head may not be preferred. The top-access socket allows the screw to be installed directly from the exposed side of the assembly.
Corrosion-Resistant & General Industrial Assemblies
Alloy steel versions are suitable for applications requiring higher mechanical strength, while stainless steel versions can be selected where corrosion resistance is more important. This makes the fasteners suitable for industrial equipment, outdoor assemblies, processing equipment, and other environments where material selection is an important part of fastener specification.