Description
The #4-40 Button Head Cap Screw is a micro-diameter, precision fastener engineered for flush, low-profile installations in tightly spaced or lightweight assemblies. With its rounded button-style head and internal hex drive, this screw offers a clean, snag-resistant finish and secure torque application—ideal for electronics, instrumentation, and miniaturized mechanical components.
Specifications
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Thread Size: #4-40 (Unified National Fine)
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Head Type: Rounded button head with internal hex socket
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Drive Type: Hex socket (Allen)
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Length: Available in standard lengths (typically from 1/8" to 1")
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Material: Alloy steel; also available in stainless steel, zinc-plated, or black oxide finishes
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Finish Options: Black oxide, plain, zinc-plated, or stainless
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Grade: Typically Grade 8 (for alloy steel), or 18-8 / 316 stainless steel for corrosion resistance
Key Features
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Ultra Low-Profile Head: The rounded button head ensures a smooth, professional finish in visible or clearance-sensitive locations.
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Fine Thread Engagement: The #4-40 thread pitch offers tight, vibration-resistant fitment in thin-wall or tapped assemblies.
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Compact Drive Control: Internal hex drive supports precision torque without damaging delicate components.
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Corrosion-Resistant Finishes: Stainless and coated options allow for long-term performance in moisture-prone or controlled environments.
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Miniature Strength: Compact yet strong enough for use in precision fastening where standard screws would be oversized or intrusive.
Typical Applications
The #4-40 Button Head Cap Screw is ideal for miniature, precision-critical assemblies such as:
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Circuit Board Mounting and Electronics Hardware
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Small Instrumentation and Sensor Assemblies
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Robotics, Drones, and Mechatronics
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Control Panels and Faceplates
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Prototyping, 3D Printing, and DIY Projects
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Laboratory and Test Equipment
