A spade drill bit is designed for use in wood. The spade drill bit has a wide, paddle-like cutting end that features a prominent point in the center. The point is used to center the drill bit in the area that is to be drilled. The wide, flat cutting end is commonly equipped with double cutting edges. The ends of the cutting edges of the spade drill bit are equipped with small, protruding cutters that are intended to cut the wood fibers at the outer edge of the hole, producing a smoother edge.
One of the most common uses for the spade drill bit is to bore large holes in wall studs in order to thread wiring and plumbing through the wall. The flat, paddle-like portion of the spade drill bit has a hole drilled in the center. This hole allows the user to attach a length of wire to the drill bit and pull it through the newly bored hole. This can save time over using a fishing wire to thread the wiring through a building's walls. Unlike many types of drill bits, the spade or paddle drill bit, as it is also known, does not benefit from the use of a pilot hole in order to drill a large diameter hole.
Attempting to use a pilot hole often creates a centering problem when using a spade drill bit. The pointed center is more than sufficient to locate the boring hole and the sharp cutting edges provide ample ability to create a large-diameter hole in even the hardest of woods. The typical use of a power drill motor is routinely limited to slow to moderate speeds when using a spade drill bit. Excessive speed can cause the bit to burn the wood, causing damage to both the wood and the drill bit.
Unlike some drill bits, the paddle bit does not pull itself into the wood. This drill bit requires applied force to push the bit into the wood as it cuts a path through the material. In cases where the finished hole will remain hidden, such as inside a wall, the user can simply push the bit completely through the wood. In cases where the finished hole might be visible, a smoother hole is commonly created by removing the spade drill bit from the hole as soon as the point emerges through the wood. The user can then place the point of the spade drill bit into the hole on the unfinished side of the bore and complete the cut, causing the bit to break through the wood on the inside of the hole.