metric structural bolts

Secondly,the desired holding power is another important factor to consider when selecting the correct wedge, bolt, and drill size. The holding power of a fastener is determined by its diameter, length, and thread pitch. Generally speaking, larger fasteners with higher thread pitches provide greater holding power. However, it's important to ensure that the fasteners you select are appropriate for the thickness of the material being fastened. If the fasteners are too large for the material, they may not be able to penetrate the material fully, resulting in reduced holding power.

...

The head of a self-drilling screw is typically made from nylon, a synthetic polymer known for its durability, resilience, and resistance to chemicals. This material choice serves several purposes. Firstly, the nylon head provides an excellent grip, reducing the chances of slippage during tightening, making it ideal for applications where a secure hold is essential. Secondly, nylon is non-conductive, making these screws safe to use in electrical installations. Lastly, the low friction coefficient of nylon allows the screw to glide smoothly into the material, minimizing the risk of damage.

...