304 - Stainless steel - Hexagon socket countersunk head screw

Why Choose 304 Countersunk Screws?

In applications where surface smoothness is critical—such as on handrails, sliding tracks, or wear plates—a protruding bolt head is not an option. The 304 countersunk screw solves this problem. By recessing the head into the material, it allows moving parts to pass over the fastener without interference. Combined with the bright, rust-free finish of A2 stainless steel, it ensures that the assembly remains functional and visually appealing for years.

Material Specifications: A2-70

Chemical Composition: Grade 304 is the most widely used austenitic stainless steel, containing 18% Chromium and 8% Nickel. This composition creates a self-passivating oxide layer that protects the screw from rust in normal humidity. It is highly resistant to oxidizing acids and common household chemicals. Mechanical Performance: These screws are typically supplied as Class 70 (A2-70). This designates a minimum tensile strength of 700 N/mm². While strong, it is important to note that due to the geometry of the countersunk head (which has less material than a cap screw head), the torque capability is slightly lower. Care should be taken to ensure the internal hex drive is not stripped during installation.

Quality Assurance

We are committed to quality transparency. An EN 10204 3.1 Material Certificate is available upon request to verify the chemical composition of the A2 stainless steel. Please note that third-party inspection services require an additional fee.

Typical Applications

304 countersunk screws are the standard for non-marine flush fastening:

• Furniture Making: Assembling metal frames and wooden components where screw heads must be hidden or flush.
• Architectural Fittings: Door hinges, window frames, and glass clamps.
• Machine Guards: Securing clear plastic or metal panels where a smooth surface is safer for operators.
• 3D Printing: Bed leveling and frame assembly on printers.

Frequently Asked Questions

Can I use A2 countersunk screws outside?

Yes, for most general outdoor applications, Grade 304 (A2) is perfectly adequate. It will resist rain and normal weather conditions. However, if you are located near the coast or in a heavily polluted industrial area, we recommend upgrading to Grade 316 (A4) to prevent cosmetic surface staining.

Do I need a washer with a countersunk screw?

No. Countersunk screws are designed to be used without washers. The conical head bears directly against the countersunk hole in the material. Adding a standard flat washer would prevent the head from sitting flush, defeating the purpose of the screw. However, special "countersunk washers" (cup washers) exist for decorative surface mounting.

What tool do I need to prepare the hole?

To install these screws correctly, you need a 90-degree countersink drill bit. After drilling the pilot hole for the thread, use the countersink bit to chamfer the top of the hole. This creates the conical seat for the screw head to rest in, ensuring a perfectly flush finish.