A wood boring drill bit is a device used in conjunction with a handheld power drill to create large diameter holes in a piece of wood. The spade wood boring drill bit is most commonly used; this bit features a sharp, angular tip that penetrates the wood, and two paddles that cut the diameter. This design is effective for boring into wood quickly. The drill must be set to a high speed setting; this bit can, however, cause splintering on the edge of the hole, though some bits feature spurs on the paddles to prevent such splintering.
Another type of wood boring drill bit is the self-feeding bit, which actually pulls the bit deeper into the wood as it drills. This relatively new device is meant to make the process of boring much easier, and also to reduce splintering or cracking sometimes associated with the use of the spade-style wood boring drill bit. While these bits do tend to reduce splintering, the cost of the devices can be quite a bit higher than more traditional spade-style wood boring drill bit models. Both types of bits can be purchased individually or as sets; many carpenters will purchase sets so holes of various diameters can be drilled on the job.
Both types of bits use an angular shank instead of a round one that is common on other types of drill bits. This is done because the shape of the bits can cause slipping, so by squaring off the shank, the drill will have more purchase and less likelihood of slipping. Sometimes only part of the shank is angled off, both to keep the cost of the bit down due to less machining, and to provide a smooth surface that will not accidentally mar the edge of the drilled hole.
Spade bits cannot cut flat-bottomed holes, so when such a hole is required, a Forstner bit is used. This wood boring drill bit can drill flat-bottomed holes, making it a good choice for cutting through veneer that has already been glued or secured in place. Unlike spade bits and self-feeding bits, however, the Forstner bit usually cannot be used with hand drills because exceptional force must be applied in order to get the bit to begin cutting. The Forstner wood boring drill bit is usually mounted in a drill press instead so consistent high pressure can be applied.