Characteristics of drill bits
There are several standard aspects of drill geometry: spiral, sharp corner, lip corner, and functional length.
Spiral drill bit
Helix (sometimes called twist rate) is the steepness of the groove that spirals along the edge of the bit. If this is steep, the drill will tend to cut faster (per revolution). This is called "long slot". It usually uses a lower spindle speed. The "compact flute" is a flatter spiral that produces more grooved rings along the length of the drill bit. This tends to cut slower (per revolution) and use a higher spindle speed. This is usually used when the material being drilled is prone to wear on the drill bit or block the hole. Aluminum and copper are common examples.
Point corner
This is the angle of the top edge. This affects the way the drill bit cuts certain materials. Softer materials require sharper corners (darker corners tend to slide along the surface and cannot bite the material). Harder materials require larger sharp corners because larger angles bite into the material and can better withstand the higher impact and resistance of harder materials. When used with harder materials, the sharper corners tend to become dull, or they may bite in and restrain the drill bit-which may damage the tip or shaft.