The auger drill bit is intended to be used in wood and is equipped with a very thick and deep spiral flute along the twist of the bit. This deep flute is designed to remove the wood chips from the hole being drilled in a much more effective manner than a typical twist drill bit. Originally designed for use only in a hand brace, the modern auger bit is designed to be used in a power drill motor. The typical auger drill bit is fitted with a screw-like point designed to pull the bit into the wood in a self-feeding manner.
It is easy to distinguish a hand-brace bit from an auger drill bit that is designed to be used in a drill motor. The hand-brace type bit is manufactured with a tapered, square area at the end of the shank designed to lock into the jaws of the hand brace chuck. There are two distinct versions of the auger bit: the Jennings and the Irwin. Both bits are similarly designed, however, the Jennings-style auger bit has two flutes that carry the wood chips up and out of the hole. The Irwin has one flute that goes completely up the drill bit and one that only goes half-way up the bit.
The Jennings auger drill bit design is the oldest of the auger-type bits, having been created in the mid-19th century. The Irwin design was first invented in 1884 and patented the following year. Occasionally called a ribbon bit due to the design of the bit resembling a coiled piece of ribbon, the edges of the wide flutes are typically sharp and can cause injury if not properly used. The screw point is very important, as it holds the bit square in the drilling location and prevents the bit from wandering when the hole is initially started.
The cutting head of the auger drill bit is virtually two plane-type blades mounted under the center screw point. Two spurs on the outer edge of the cutting planes are designed to cut the wood fibers as the screw point pulls the bit into the wood. The purpose of the screw point is to pull the auger bit into the wood, thereby eliminating the need for the user to force the bit into the wood. The user need only provide the power to turn the drill bit, and this is often seen as a great advantage when using a hand brace.
