Metal drill bits are available in a number of shapes and sizes. The design of the bits depends on both the desired size of the hole and the material into which it is being drilled. While most metal drill bits are made from some type of steel or steel alloy, some tasks may require harder bits made from composite materials such as tungsten carbide. Attempting to use a softer drill bit on a material that it is not designed for it can damage the drill and cause serious injury, so it is important for people to use bits only for their intended purposes.
Carbon steel bits are primarily used to drill holes in wood, but some of the higher carbon bits also can be used on metal. While these are generally the cheapest metal drill bits available, carbon bits lose their sharpness faster and can overheat when drilling into metal surfaces. Carbon bits are primarily useful for odd jobs around the house and woodworking tasks.
High-speed steel (HSS) bits are made from tougher steel alloys that have a higher tolerance for heat. These bits are used in manufacturing and other applications that require the bit to be in constant use. HSS bits also may be coated with another material to make them last longer or perform better in certain applications. When drilling through more resilient materials, it may be necessary to use a drill press to keep the bit at the correct angle and position.
Drilling into very hard materials, such as stainless steel, may require a cobalt steel alloy. While these bits are usually more expensive, they are specifically designed to deal with tougher materials and will usually hold their edge longer. Cobalt alloy bits are usually more brittle than other metal drill bits, so users will need to use caution to avoid damaging their tools and materials.
Composite materials such as tungsten carbide are used to make bits and drill bit tips for use when drilling into brick, concrete and other masonry materials. These bits can be included in sets along with masonry screws and anchors or sold separately by size. Carbide bits usually retain their sharpness longer than other bits and are often used for certain industrial applications. Tungsten carbide also is used to form the support stem for more exotic drilling tools that use polycrystalline diamond (PCD) as their cutting surface. These are typically very expensive bits used for precision industrial applications.