Hex Socket Countersunk Bolts - Black - M5 x 20mm

Countersunk bolts are measured from the very top of the flat head down to the tip of the screw.

You will need a hex socket (Allen key) of the appropriate size for the bolt's drive type. For M5 bolts, this is typically a 4mm hex key.

Grade 10.9 indicates the bolt's material strength. It signifies a minimum tensile strength of 1000 MPa and a yield strength of 900 MPa, denoting high-strength steel.

The black oxide finish provides good corrosion resistance, making them suitable for many outdoor applications. However, for extremely harsh or constantly wet environments, stainless steel alternatives might offer superior long-term protection.

Yes, these bolts are designed for use with standard metric nuts or threaded holes that match their M-thread size. Ensure the nut material and grade are appropriate for the application's strength requirements.

The primary advantage is that the head sits flush with the surface, providing a smooth, clean finish and preventing potential snagging or protrusions.

The 'M' size refers to the nominal major diameter of the thread in millimeters. Choose the M size based on the required shear strength and the size of the holes in the materials you are joining. Larger M numbers generally indicate stronger, thicker bolts.

Ensure the pre-drilled hole has a correct 90° countersink angle and is sufficiently wide to accept the bolt head. Verify the bolt length is appropriate for the material thickness.

Use a high-quality hex key that fits snugly. Apply steady, even pressure and avoid excessive force if resistance is met; check for thread damage or obstructions.

Check that the mating threads are not stripped or damaged. Ensure the correct size bolt is used for the tapped hole or nut. Re-tighten, applying appropriate torque.

While the black oxide finish offers corrosion resistance, prolonged exposure to harsh conditions can still cause rust. Clean affected areas and consider applying a protective coating if necessary.