Spade bit with improved cutting geometry

A spade bit includes a shaft defining an axis, and a blade attached to the shaft and having a first blade portion and a second blade portion. The first blade portion defines a first leading face portion, and the second blade portion defines a second leading face portion. The first blade portion defines a first cutting edge portion, and the second blade portion defines a second cutting edge portion. The first cutting edge portion lies on a first border portion of the first leading face portion, and the second cutting edge portion lies on a second border portion of the second leading face portion. The first cutting edge portion and the second cutting edge portion both lie in a plane P. An area A is bound by the plane P and the first leading face portion when the first blade portion is viewed in a first cross section taken along a plane P which is parallel to and spaced apart from the axis by a distance D, and the area A increases as the distance D increases. The area A is bound by the plane P and the second leading face portion when the second blade portion is viewed in a second cross section taken along a plane P which is parallel to and spaced apart from the axis by a distance D, and the area A increases as the distance D increases.