UNC A2/304 Stainless Steel Countersunk Socket Cap Machine Screws - Allen Drive Bolts

Roll over image to zoom in Click on image to zoom

UNC A2/304 Stainless Steel Countersunk Socket Cap Machine Screws - Allen Drive Bolts

HomeDIYer

No reviews

By HomeDIYer®

Product Size: 2#-56x1

Pack of Quantity (Pcs): 1

Price:

$2.03 USD

Stock:

In stock (500 units), ready to be shipped

Quantity:

Share this product

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

DIY Expert Support

Get fitment advice & recommendations

Mon–Fri 8:30 AM – 8:00 PM

WhatsApp Email Us

24-Hour Fast Ship

Arrives in 3–14 Days

Worldwide Shipping

30-Day Returns

1 tree planted with every purchase

UNC Countersunk Socket Cap Screws in A2 Stainless Steel — Flush Fastening Made Easy

When a protruding screw head isn't an option — whether you're assembling electronics enclosures, mounting panels, or building precision woodwork — a countersunk socket cap screw is the go-to solution. DIYers, machinists, and fabricators who need a clean, flush surface without sacrificing holding strength rely on this style of fastener daily.

Each screw is machined from A2/304 stainless steel and features a flat (countersunk) head with an internal hex (Allen) socket drive. Available in UNC thread sizes from #2-56 through 5/16-18, with lengths ranging from 1/4" (≈6.4mm) to 2" (≈50.8mm). Sold individually or in packs of 3, 5, or 20 — so you can grab exactly what your project needs.

Typical use cases include flush-mounting circuit board standoffs, securing aluminum extrusion panels, assembling furniture hardware, and fastening thin sheet metal where a flat surface is critical. These UNC countersunk Allen bolts are a staple for anyone working with inch-standard components in the US.

🔩 Thread Compatibility: UNC (Unified National Coarse) thread standard — fits all standard UNC nuts, inserts, and tapped holes. Not compatible with metric threads.

⚠️ Countersink Angle: These screws use an 82° head angle (US inch standard). Use an 82° countersink bit — not the 90° metric type — for a proper flush fit.

✅ Key Features of These UNC Countersunk Socket Cap Screws

🔩A2/304 Stainless Steel Construction — Resists rust and oxidation in indoor and light outdoor environments; suitable for general-purpose corrosion-resistant fastening applications.
🔧Internal Hex (Allen) Socket Drive — Allows high torque application in tight spaces where a Phillips or slotted driver won't fit; compatible with standard inch hex keys.
📐Flat Countersunk Head Profile — Sits flush with or below the surface when installed in a properly countersunk hole, eliminating snag points on panels, enclosures, and furniture.
📏Wide UNC Size Range — Covers #2-56, #4-40, #6-32, #8-32, #10-24, and 5/16-18 thread sizes with multiple length options, making it easy to find the right fit for your specific application.
📦Flexible Pack Quantities — Available in 1, 3, 5, or 20-piece packs so you can order exactly what you need — whether it's a single replacement or a small project supply.
🏭Precision Machined Threads — UNC threads are cut to standard tolerances for consistent fit and reliable engagement in tapped holes, threaded inserts, and standard UNC nuts.

📐 Technical Specifications — UNC Countersunk Socket Cap Screws

Material	A2/304 Stainless Steel
Drive Type	Internal Hex (Allen / Socket)
Head Style	Flat Countersunk (CSK)
Head Angle	82° (US inch standard)
Thread Standard	UNC (Unified National Coarse)
Available Thread Sizes	#2-56, #4-40, #6-32, #8-32, #10-24, 5/16-18
Available Lengths	1/4" (≈6.4mm) to 2" (≈50.8mm) — see variant options
Pack Quantities	1, 3, 5, or 20 pieces
Finish	Natural stainless (uncoated)
Tensile Strength	Typically 500–700 MPa (A2 grade)
Recommended Countersink Bit	82° inch-standard countersink bit
Compatible Standards	ASME B18.3 (Socket Screws), UNC thread per ASME B1.1

❓ Frequently Asked Questions

How do I choose the right size and length for my project?

Match the thread size to your tapped hole or nut (e.g., 6#-32 means #6 diameter, 32 threads per inch). For length, measure the material thickness and add enough thread engagement — typically 1.5× the screw diameter into the receiving material. For example, a 1/4" (≈6.4mm) screw suits thin sheet metal, while a 1" (≈25.4mm) screw works for thicker assemblies. Always countersink the hole to match the 82° head angle for a flush finish.

What load or clamping force can these screws handle?

A2/304 stainless steel typically has a tensile strength of around 500–700 MPa, which is generally sufficient for light-to-medium structural and mechanical applications. Exact load capacity depends on the screw size, thread engagement, and base material. For critical load-bearing applications, consult an engineer or refer to published fastener load tables.

Are these screws suitable for outdoor or marine use?

A2/304 stainless steel offers good corrosion resistance and is generally suitable for outdoor environments, including light marine exposure. However, for highly aggressive saltwater or coastal environments, A4/316 stainless steel is typically recommended for superior chloride resistance.

What thread standard do these use — are they compatible with standard nuts and tapped holes?

These screws follow the UNC (Unified National Coarse) thread standard, the most common inch-based thread system in the US. They are compatible with standard UNC nuts, inserts, and tapped holes of the matching size and thread pitch (e.g., 6#-32 fits any standard #6-32 UNC nut or tapped hole). They are not compatible with metric threads.

What Allen key (hex key) size do I need to drive these screws?

The required hex key size varies by screw diameter. As a general guide: #2 screws typically use a 0.05" hex key, #4 use 3/64", #6 use 1/16", #8 use 5/64", #10 use 3/32", and 5/16" screws use 3/16". Always verify with the specific fastener spec sheet or test-fit before driving to avoid stripping the socket.

Can I use these in aluminum, plastic, or wood?

Yes. These countersunk socket cap screws are commonly used in aluminum enclosures, plastic panels, and hardwood assemblies where a flush surface is required. For softer materials like plastic or wood, pre-drilling and countersinking is recommended to avoid splitting. In aluminum, thread-locking inserts (e.g., Helicoil) can improve thread strength and longevity.

What is the head angle of these countersunk screws, and why does it matter?

UNC countersunk socket cap screws generally have an 82° head angle, which is the standard for inch-series fasteners in the US. This differs from the 90° angle common in metric countersunk screws. Using the wrong countersink angle will result in the head sitting proud of the surface or rocking in the hole — so be sure to use an 82° countersink bit for a proper flush fit.

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