The first part of the bit to make contact with the wood is the brad point. This bites into the grain and prevents the bit from being able to move around.
As the bit descends, the spurs trace around the edge of the bore hole, cutting around the circumference of the hole. When boring through wood, the spurs shear neatly through the fibres of the wood so that they will not buckle under pressure.
Very quickly afterwards, the lips of the bit make contact with the material’s surface and begin to cut away any waste that has been left behind by the spurs. This is pushed up through the flutes and out of the bore hole.
As the spurs continue to rotate, they make a very clean cut around the edges of the hole all the way down, continuing to sever fibres and preventing splinters from forming in fibrous materials.
This is also true of tungsten carbide and polycrystalline diamond-tipped bits that cut through kevlar-reinforced materials. Kevlar is fibrous, so each time the bit reaches a Kevlar layer, the spurs make a clean cut and prevent fuzz (fibres that have frayed or caught on the drill bit and are protruding into the borehole) from forming.
If the fibres were not cut properly, the exposed fibres in the fuzz could catch on bolts or screws that were inserted into the borehole on an assembly line, which could result in the layers of the composite material being pulled apart. This is known as delamination.
