Cap Head Socket Screws with Half Thread — Reliable Metric Fasteners for Precision Assembly
When a loose fit or stripped thread ruins a project, the fastener is usually the culprit. Makers, engineers, and repair technicians who work with electronics enclosures, aluminum frames, and mechanical assemblies need cap head socket screws they can trust to seat flush, clamp tight, and stay put — without rounding out under torque.
Each set contains 20, 50, or 100 pieces of cap head hex socket screws with a half-thread (partial thread) shank. Available in M2, M2.5, M3, and M4 thread diameters with lengths ranging from 6mm (≈1/4") to 45mm (≈1-3/4"). Choose between a nickel-plated finish for a clean silver look or a black zinc finish for a matte, low-profile appearance.
These metric socket head cap screws are widely used in 3D printer frame assembly, RC car chassis builds, electronics enclosure mounting, and DIY CNC machine construction — anywhere a hex Allen drive and a clean cylindrical head profile are required.
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Compatibility: ISO metric thread standard (M2 / M2.5 / M3 / M4). Fits standard metric nuts, threaded inserts, and tapped holes per ISO 68-1. Driven with a standard hex Allen key (1.5mm / 2mm / 2.5mm / 3mm respectively).
✅ Key Features of These Cap Head Hex Socket Screws
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🔩Half-Thread Shank Design — The unthreaded shoulder section improves part alignment and maximizes clamping force between two mating components, a critical advantage in precision mechanical assembly.
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🎯Cylindrical Cap Head Profile — The tall, cylindrical head provides a larger bearing surface than a flat-head screw, distributing load evenly and reducing the risk of pull-through in softer materials like aluminum or plastic.
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🔑Hex Allen Socket Drive — The internal hex socket allows high torque application in tight spaces where a standard screwdriver cannot reach, making these ideal for recessed mounting holes in 3D printer frames and CNC builds.
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🛡️Two Finish Options — Nickel-plated for a bright, corrosion-resistant appearance in visible assemblies; black zinc for a matte, low-reflectance look in electronics and tactical equipment builds.
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📐Wide Size Range — Covers M2 through M4 in lengths from 6mm to 45mm, letting you stock a single listing to cover most small-to-medium metric fastener needs across multiple projects.
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📦Flexible Pack Quantities — Available in 20, 50, or 100-piece packs so hobbyists can grab a small quantity for a one-off repair while workshop users can stock up at a lower per-piece cost.
📐 Technical Specifications — Cap Head Socket Machine Screws
| Thread Standard |
ISO Metric (M2 / M2.5 / M3 / M4) |
| Thread Type |
Half thread (partial thread / shoulder shank) |
| Head Style |
Cap head (cylindrical / socket head) |
| Drive Type |
Hex Allen socket (internal hex) |
| Hex Key Size |
M2 → 1.5mm | M2.5 → 2mm | M3 → 2.5mm | M4 → 3mm |
| Available Diameters |
M2, M2.5, M3, M4 |
| Available Lengths |
6mm (≈1/4") to 45mm (≈1-3/4") — see variant options |
| Surface Treatment |
Nickel plated or Black zinc — select above |
| Pack Quantity |
20 pcs / 50 pcs / 100 pcs — select above |
| Material |
See variant options / Contact us to confirm grade |
| Tensile Strength |
Contact us to confirm |
| Thread Pitch |
M2 → 0.4mm | M2.5 → 0.45mm | M3 → 0.5mm | M4 → 0.7mm (standard coarse) |
| Country of Origin |
See variant options |
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Note: If you need to confirm exact material grade, tensile strength, or RoHS compliance for your application, please contact us before ordering.
❓ Frequently Asked Questions
How do I choose the right screw length for my application?
A general rule of thumb is to select a length that allows the screw to penetrate the base material by at least 1.5× the thread diameter. For example, an M3 screw typically needs at least 4.5mm of thread engagement. Available lengths in this listing range from 6mm (≈1/4") to 45mm (≈1-3/4"). Measure your stack-up thickness first, then subtract the unthreaded shank length to confirm adequate thread engagement.
What is the load-bearing or clamping strength of these screws?
Tensile and shear strength depend on the base material grade. These cap head socket screws are generally manufactured to a medium-strength grade suitable for general mechanical assembly. For safety-critical or high-load applications, please contact us to confirm the exact grade and verify suitability before ordering.
Are these screws suitable for outdoor or corrosion-prone environments?
The nickel-plated finish provides moderate corrosion resistance suitable for indoor and light-duty outdoor use. The black zinc finish offers similar protection with a matte black appearance. For harsh outdoor, high-humidity, or marine environments, stainless steel fasteners are generally recommended instead.
What thread standard do these screws use — are they compatible with standard metric hardware?
These screws use the ISO metric coarse thread standard (M2, M2.5, M3, M4). They are compatible with standard metric nuts, threaded inserts, and tapped holes following ISO 68-1 specifications. They are not compatible with UNC/UNF inch-standard hardware.
What does "half thread" mean and when should I use it instead of a fully threaded screw?
Half thread (also called partial thread) means only the lower portion of the shank is threaded, while the upper portion is smooth. This design allows the unthreaded shank to act as a shoulder, providing better alignment and stronger clamping force between two parts. It is ideal for applications where you need to pull two components tightly together — such as joining an aluminum plate to a frame — rather than threading into a single piece of material.
What hex key (Allen wrench) size do I need to drive these screws?
The required hex key size follows standard ISO socket head cap screw specifications: M2 typically uses a 1.5mm hex key, M2.5 uses 2mm, M3 uses 2.5mm, and M4 uses 3mm. Always do a test fit before final assembly to confirm the correct key size.
Can I use these screws in aluminum, plastic, or wood?
Yes. These cap head socket screws are commonly used in aluminum enclosures, plastic housings, and light woodworking jigs. For plastic or soft materials, pre-drilling a pilot hole and using a threaded insert is generally recommended to prevent stripping. In aluminum, tapping the hole to the correct metric pitch before installation will give the best results.
🛒 Select your size, length, finish, and quantity above, then add to cart — ships from our US warehouse.
