Black Hex Socket Countersunk Bolts - M8 X 25mm

Unlike standard cap head screws, the length of a countersunk bolt is measured from the very top of its flat head down to the tip of the screw thread.

These bolts are made from High Tensile Carbon Steel, specifically Grade 10.9.

You will need a metric hex key (Allen wrench). For M8 bolts, this is typically a 5mm hex key.

The black oxide finish offers corrosion resistance, making them suitable for many outdoor applications. However, for prolonged exposure to harsh weather, additional protective measures like paint or sealant may be beneficial.

These are international standards that specify the dimensions, tolerances, and mechanical properties for countersunk head cap screws. Using bolts that meet these standards ensures consistency and compatibility.

Yes, the flat countersunk head sits flush with the surface and the black finish provides a clean, professional look, making them suitable for visible applications where aesthetics are important.

The black oxide finish provides a visually appealing matte black appearance and offers a degree of corrosion resistance.

The hole may not be sufficiently countersunk, or the hole's angle is incorrect. Ensure the hole is drilled to accommodate a 90° countersunk head and that the material is compatible with countersinking.

Ensure you are using the correct size metric hex key. Apply firm, consistent pressure and avoid jerky movements. If stripping has occurred, the bolt may need to be removed using specialized tools or replaced.

Verify that the M8 size and Grade 10.9 rating are sufficient for the load requirements. For heavier loads, consider larger diameter bolts or higher tensile strength grades if available.

This is normal wear for black oxide finishes under friction or stress. For critical aesthetic applications, handle with care during installation or consider a different finish if extreme durability is required.