US Patent 7246976 Spade bit

An embodiment of a spade bit has straight grooves at a lead angle of 4 to 8 degrees placed on flat edges of the spade bit. In an alternative embodiment, a spade bit has two steps of straight grooves at a lead angle of 4 to 8 degrees placed on flat edges of the spade bit. In other alternative embodiments, a spade bit has tapered flat edge which have straight grooves at a lead angle of 4 to 8 degrees placed thereon. The straight grooves on the flat edges of the spade bits allow the spade bit to pull itself through the workpiece with a minimal amount of penetration. The flat edges of the spade bit may also have cutting surfaces for cleaning the hole and permitting the easy removal of the spade bit from the hole after drilling.