High-speed steel (HSS) drill bits are a type of tough, durable drill bit traditionally used for high-volume production drilling. Production drilling involves fast, repetitive drilling with few — if any — breaks between tasks. Many manufacturers exclusively produce drill bits that employ HSS construction because they are so versatile. HSS drill bits contain key elements such as carbon, and are often used to work on other types of metal including aluminum and other softer grades of steel. Many hand tools are made with machines that feature HSS cutting attachments and drill bits.
In general, the only way to drill through a hard substance is to employ a drill bit made out of a material that is even harder. For example, an HSS drill bit would be ideal for drilling through aluminum but not granite or quartz because they are much harder than HSS metals. Despite its solid construction, an HSS drill bit will wear away quickly while attempting to drill through materials such as granite.
HSSs contain certain percentages of carbon, tungsten, cobalt, chromium, molybdenum and other elements. Just like all steels, HSSs contain a majority percentage of iron as a base metal. The carbon and chromium in HSS add toughness and strength to the material. Chromium also adds corrosion-resistant properties to HSS.
An HSS drill bit needs to be hard and durable but must also offer some level of flexibility to prevent breakage; for this reason, the metal molybdenum is often added. Regular production drilling results in friction that causes intense heat, so drill bits and workpieces can reach very high temperatures during the production drilling process. Tungsten has the highest melting point of any metal. While tungsten increases hardness, it also greatly increases the heat-resistance of HSSs. Cobalt is also added to increase the HSS's resistance to heat.
There are several grades of high-speed steels, including M1, M2 and M50 HSSs. M1 HSS drill bits are the most expensive, hardest type of HSS drill bits available. but they are brittle and can easily break or fracture if used improperly. An M2 HSS drill bit contains more molybdenum than an M1 bit, making it more flexible than an M1. M50 drill bits are still very strong bits but they are somewhat softer than M1 bits; these can generally be purchased for slightly lower prices.
Unlike certain other types of high-performance drill bits, such as titanium bits, HSS bits can be sharpened many times before they need replacement. Titanium drill bits feature a titanium coating usually applied over a quality drill bit. Sharpening titanium drill bits will remove the titanium coating and ultimately decrease the effectiveness of the bit.