When drilling through wood, the correct type of wood drill bit should be used. Though the most common bit is the universal twist bit; spur point, flat wood and wood auger bits are used in special circumstances. Countersink bits are also used to finish off a drilled hole where countersink screws will be installed.
Twist Bit - Referred to also as a "twist drill," these bits are used in both hand and electric drills. The shank of the bit is spiral which helps remove the wood shavings from the hole while drilling. These bits are also used on metal and plastic; they are made of high speed steel --- for drilling at high speeds --- or carbon steel which is made specially for wood drilling. Care should be taken when using smaller shank twist bits, as they can get brittle if too much pressure is applied to the bit when drilling.
Spur Point Bit - Like the twist bit, the spur point bit has a twisted shank to help remove shavings from the drilled hole. Also known as a "dowel" or "wood bit," the tip has a central point with two raised spurs to quickly cut through timber leaving the sides of the drilled hole clean. This bit is ideal for drilling dowel holes.
Flat Wood Bit - Flat wood bits are used only with a power drill; the shank is flat with a sharp spike in the center of its tip. They are used to create rougher holes; they make a considerable amount of damage when exiting through the backside of the wood. These bits are not used for widening existing holes as they jump about when the flat side edges of the tip meet with the wood surface.
Wood Auger Bit - The wood auger bit is used for drilling both deep or large diameter holes. The bit's head has a central, threaded single spur, with the twisted shank removing wood from the hole while drilling. It is used only with a hand brace, as its threaded spur helps to pull the bit into the timber.
Countersink Bit - Used with both a power drill or router, countersink bits have a widened lower shank. When inserted into the hole, it opens up the area around the hole so that countersink screw heads can rest either flush with, or below the wood surface.