The flat head screw with its typical countersink is the most commonly used screw.... Read More
The flat head screw with its typical countersink is the most commonly used screw. The countersink is the beveled surface under the head. The top of the head is flush with the material when the screw is seated. The countersink normally has an 80-82-degree angle. Variations of this angle are in use. Some European hardware requires a 90 or 100-degree head angle.
Another variation that has become very popular is a Flat Head with NIBS on the countersink surface. There are usually four or six ridges protruding from the surface that cut into the material as the screw head penetrates the wood. This is designed to eliminate pre-countersinking the screw hole. NIBS work very well in soft and hardwoods as well as MDF and laminates. They can also reduce splintering of the wood around the head of the screw.