Hex Socket Countersunk Bolts - M4 X 12mm - Black

Countersunk bolts are measured by their total length, from the very top of the flat head to the tip of the screw. This is different from cap head screws which are measured from below the head.

These bolts are made from High Tensile Carbon Steel, specifically Grade 10.9, known for its strength and durability.

Black oxide is a conversion coating that provides mild corrosion resistance and a matte black appearance. It is achieved through a chemical process.

The drive type is a Hex Socket, commonly known as an Allen key drive.

The black oxide finish offers some corrosion resistance, but for prolonged outdoor exposure or harsh conditions, stainless steel or other more robust coatings may be preferable to prevent rust.

M4 and M5 refer to the nominal diameter of the bolt's thread. An M4 bolt has a thread diameter of approximately 4mm, while an M5 bolt has a thread diameter of approximately 5mm. Larger numbers indicate larger, stronger bolts.

Always refer to the specific project requirements. For countersunk bolts, measure the depth of the counterbore hole and ensure the bolt's total length will sit flush or slightly below the surface as intended.

Ensure you are using the correct size Allen key. If the head is already damaged, you may need to use a screw extractor or carefully drill out the bolt.

Verify that the hole is tapped for M4 threads and that there are no obstructions or cross-threading. Ensure the bolt is entering the hole straight.

This is a cosmetic issue and does not typically affect structural integrity. For aesthetic concerns, consider replacement or applying a protective coating if feasible for the application.