A spade bit includes a shaft defining an axis about which the spade bit is configured to be rotated. The space bit also includes a blade attached to the shaft and having a first paddle portion and a second paddle portion. In addition, the spade bit includes a tip portion attached to the blade and aligned with the axis. The first paddle portion includes (i) a first leading end portion positioned on a first side of the axis and configured to define a first cutting edge portion, and (ii) a first lateral extension portion configured to define a first sloping surface. The first paddle portion defines a first relief space positioned adjacent to both the first sloping portion and the first leading end portion. The second paddle portion includes (i) a second leading end portion positioned on an opposite second side of the axis and configured to define a second cutting edge portion, and (ii) a second lateral extension portion configured to define a second sloping surface. The second paddle portion defines a second relief space positioned adjacent to both the second sloping portion and the second leading end portion.

A nail head removal tool is disclosed to be rotated by an electric drill to cut off the rusted head of a nail that has been driven into a wooden surface. The nail head removal tool includes an outer cutting body having a cylindrical cutting end with a plurality of cutting teeth extending therearound. An inner cutting insert is press fit into an insert cavity formed in the cylindrical cutting end of the outer cutting body. The inner cutting insert has a pair of cutting blades spaced from one another and standing upwardly from a cutting head of the insert. When a rotational force is applied to the tool, the cutting teeth at the cutting end of the outer cutting body cut into the surface around the nail, and the cutting blades at the cutting had of the inner cutting insert cut off and pulverize the rusted nail head.

A nail head removal tool is disclosed to be rotated by an electric drill to cut off the rusted head of a nail that has been driven into a wooden surface. The nail head removal tool includes an outer cutting body having a cylindrical cutting end with a plurality of cutting teeth extending therearound. An inner cutting insert is press fit into an insert cavity formed in the cylindrical cutting end of the outer cutting body. The inner cutting insert has a pair of cutting blades spaced from one another and standing upwardly from a cutting head of the insert. When a rotational force is applied to the tool, the cutting teeth at the cutting end of the outer cutting body cut into the surface around the nail, and the cutting blades at the cutting had of the inner cutting insert cut off and pulverize the rusted nail head.

A drill includes a blade tip part that is formed of diamond and a trunk part that is formed of diamond and is continuous with the blade tip part, the drill rotating about a drill axis, the blade tip part includes N cutting edges where N is an integer of no less than 4, and a proportion of S1 to S2 is no less than 30% and no more than 60%, where S1 is an area of the drill in a cross-section with the drill axis as a normal line, the cross-section including a boundary between the blade tip part and the trunk part, r is a maximum value of a distance from the drill axis to an outer edge of the drill in the cross-section and S2 is an area of a circle with r as a radius.