M12-M20 Socket Cap Head Screws Hex Allen Drive A2 Stainless Steel Machine Bolts

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M12-M20 Socket Cap Head Screws Hex Allen Drive A2 Stainless Steel Machine Bolts

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By HomeDIYer®

Thread Diameter: M12

Screw Lengh: 20mm

Amount: 1pcs

Price:

$2.24 USD

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In stock (500 units), ready to be shipped

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M12–M20 Socket Cap Head Screws — Reliable Hex Allen Fastening in A2 Stainless Steel

When a standard hex bolt won't fit a recessed cavity, or when you need a clean, low-profile fastening solution for machinery, frames, or structural assemblies, socket cap screws are the go-to choice for engineers, fabricators, and serious DIYers. These M12–M20 socket cap head screws deliver the torque capacity and corrosion resistance needed for demanding applications — without the bulk of a traditional hex head.

Each piece is an M12–M20 socket cap head screw machined from A2 stainless steel (304 grade), featuring a cylindrical cap head with an internal hex (Allen) drive socket. Thread diameters available: M12, M14, M16, and M20. Lengths range from 20mm (≈13/16") to 150mm (≈5-29/32") depending on diameter. Sold individually (1 pc), in pairs (2 pcs), or in sets of 5 pcs — select your combination above.

Typical use cases include CNC machine frame assembly, motor mount bolting, industrial equipment maintenance, structural steel connections, and replacement fasteners for metric machinery. The hex Allen drive socket cap screw format is widely used in applications where a flush or recessed head is required, or where wrench clearance is limited.

🔩 Compatibility: ISO metric coarse thread (DIN 912 / ISO 4762). Compatible with standard metric nuts, threaded inserts, and tapped holes. M12 = 1.75mm pitch | M14 = 2.0mm pitch | M16 = 2.0mm pitch | M20 = 2.5mm pitch.

⚠️ Note: Not all length options are available for every diameter. Please verify your required thread engagement depth and clearance before ordering. If you need a size not listed, contact us to confirm availability.

✅ Key Features of These M12–M20 Socket Cap Head Screws

🔩A2 Stainless Steel Construction — Made from 304-grade stainless steel, these socket cap screws resist rust and oxidation in indoor, outdoor, and light-moisture environments without surface coatings.
🔧Internal Hex Allen Drive — The recessed hex socket allows high torque application in tight spaces where a standard open-end wrench cannot reach, making them ideal for machine assembly and panel mounting.
📐Wide Size Range: M12 to M20 — Covers the most common large-diameter metric fastener sizes used in structural, mechanical, and industrial applications, with lengths from 20mm (≈13/16") to 150mm (≈5-29/32").
⚙️DIN 912 / ISO 4762 Standard — Conforms to internationally recognized dimensional standards for socket head cap screws, ensuring interchangeability with metric tooling and hardware across manufacturers.
📦Flexible Quantity Options — Available in 1 pc, 2 pcs, or 5 pcs per order, so you can buy exactly what your repair or project requires without overstocking.
🏭Cylindrical Cap Head Design — The tall cylindrical head provides a larger bearing surface than a flat-head screw, distributing clamping load more evenly across the mating surface in bolted joints.

📐 Technical Specifications — Socket Cap Head Machine Screws

Head Type	Socket Cap Head (Cylindrical)
Drive Type	Internal Hex (Allen / Hex Key)
Material	A2 Stainless Steel (304 Grade)
Thread Standard	ISO Metric Coarse (DIN 912 / ISO 4762)
Thread Diameters	M12, M14, M16, M20
Thread Pitch	M12: 1.75mm \| M14: 2.0mm \| M16: 2.0mm \| M20: 2.5mm
Available Lengths	20mm (≈13/16") – 150mm (≈5-29/32") — see variant options
Hex Key Size Required	M12: 10mm \| M14: 12mm \| M16: 14mm \| M20: 17mm
Tensile Strength	Typically ~700 MPa (A2-70 per ISO 3506)
Surface Finish	Natural stainless (no coating)
Quantity per Order	1 pc, 2 pcs, or 5 pcs (select above)
Country of Origin	See variant options

❓ Frequently Asked Questions

How do I choose the right length for my socket cap screw?

A general rule: the engaged thread length should be at least 1.5× the bolt diameter for steel, and 2× for softer materials like aluminum. For example, an M12 bolt threading into aluminum typically needs at least 24mm of thread engagement. Available lengths range from 20mm (≈13/16") to 150mm (≈5-29/32"). Always measure your clearance hole depth and material thickness before selecting.

What is the tensile strength of these A2 stainless steel socket cap screws?

A2 stainless steel (304 grade) socket cap screws generally have a tensile strength of approximately 700 MPa and a proof load stress of around 450 MPa per ISO 3506. For higher-load applications, A4-80 or grade 8.8 carbon steel may be more appropriate. Contact us to confirm specific load ratings for your application.

Are these screws suitable for outdoor or marine use?

A2 stainless steel offers good corrosion resistance in most outdoor environments and is generally suitable for light marine exposure. For harsh saltwater or chemical environments, A4 (316) stainless steel is typically recommended. These screws are not coated, so their corrosion resistance comes from the base alloy itself.

What thread standard do these socket cap screws use?

These screws use ISO metric coarse thread (ISO 261 / DIN 912 standard), which is the most common metric thread pitch used in machinery and equipment worldwide. M12 typically has a 1.75mm pitch, M14 a 2.0mm pitch, M16 a 2.0mm pitch, and M20 a 2.5mm pitch. They are compatible with standard metric nuts and threaded inserts.

What hex key (Allen wrench) size do I need for each diameter?

Per DIN 912 / ISO 4762 standards: M12 typically requires a 10mm hex key, M14 a 12mm hex key, M16 a 14mm hex key, and M20 a 17mm hex key. Always use a properly fitting key to avoid rounding the socket.

Can I use these socket cap screws in aluminum, plastic, or wood?

Yes, these socket cap screws can generally be used with aluminum (with appropriate threaded inserts or tapped holes), and in some structural wood applications with pre-drilled clearance holes. They are not self-tapping. For plastic, thread engagement depth and material hardness should be verified to avoid stripping.

What is the difference between A2 and A4 stainless steel for machine bolts?

A2 (304 stainless) is the most common grade, offering good corrosion resistance for general indoor and outdoor use. A4 (316 stainless) adds molybdenum for superior resistance to chlorides and saltwater. For most DIY, mechanical, and light industrial applications, A2 is sufficient. For marine or chemical environments, A4 is generally preferred.

🛒 Select your thread diameter, length, and quantity above, then add to cart — ships from our US warehouse.