M5 Socket Countersunk Screws (DIN 7991) in self-colour high tensile steel (10.9) are specific types of screws with particular characteristics:
M5: This refers to the metric thread size of the screw. ie, M5 indicates that the diameter of the screw is 5 millimetres.
Socket: These screws have a socket (hexagonal) drive, which means you'll need a hex key or Allen wrench to install or remove them. The socket drive design provides a more secure and efficient way to apply torque compared to other drive types like slotted or Phillips.
Countersunk: Countersunk screws have a conical head with a flat top. They are designed to sit flush with the surface when installed, giving a neat and smooth finish.
DIN 7991: This refers to the standard or specification that the screw follows. DIN 7991 is a standard that specifies the dimensions, tolerances, and other requirements for socket countersunk screws.
Self Colour: "Self-colour" means that the screws have not undergone any surface finishing treatment like plating or coating. They are made of plain steel and may be susceptible to corrosion, so they are often used in applications where appearance is not a concern, and other corrosion protection methods are employed.
High Tensile Steel (10.9): This indicates the strength and material grade of the screws. "High tensile" means that the steel used is strong and can withstand a significant amount of tensile (pulling) force. The "10.9" is a classification that specifies the hardness and strength of the steel. In this case, 10.9 indicates a tensile strength of 1000 N/mm² and a minimum yield strength of 900 N/mm².