Drill bits are a type of cutting tool to drill holes in work materials. They are used with machine tools such as drill press, lathe, milling machine and machining center. Drill bit materials include alloy carbide, high speed steel powder, high-speed steel, and some of them have coatings such as silicone-based, TiAlN-based, TiCN-based, TiN-based coatings, or surface treatment such as steam oxide treatment for enhanced oil retention on surface. Additionally, there is also a type of machining called thinning, given to the bit tip to reduce the thrust load applied to it when drilling. There are different shapes of thinning such as X-shape (for machining deep holes), R-shape (for machining stainless-steel-based workpieces) and S-shaped (for machining cast-iron- or non-ferrous-based workpieces); each one of them is used accordingly for different features and applications. In recent years, flat drill bits, which can drill holes without bending even on round surfaces, are attracting attention.