For most household projects, a high speed steel drill bit is sufficient. When you're drilling through hardened steel, however, a strong, heat-resistant drill bit is needed. A titanium drill bit is good enough for most home projects. However, if you do a lot of drilling into hardened steel, a cobalt drill bit, although expensive, will provide long-lasting performance.
Hardened steel includes such metals as titanium, stainless steel and iron. It is produced by heating steel to a hardening temperature of between 1,450 and 1,500 degrees Fahrenheit. The steel is then cooled rapidly by placing it into an oil bath. The resulting steel is used in the manufacture of bolts, screws, machinery parts, safes and construction materials. It can be difficult to determine whether a metal is hardened steel or not. If the metal cannot be filed, it is most likely hardened steel. Sheet steel is not typically hardened.
Cobalt Drill Bits
Cobalt drill bits are strong enough to penetrate stainless steel, titanium, nickel and iron. The drills are made of cobalt alloy that is embedded throughout the bit, producing a strong product that can penetrate these hard, abrasive materials and withstand high temperatures. If a cobalt drill bit becomes dull, you can sharpen it without affecting its strength. Cobalt drill bits are typically used in industrial applications and for repeated drilling projects.
Titanium Drill Bits
Titanium drill bits have a strong titanium coating for good surface hardness and resistance to corrosion. The titanium coating on these bits reduces friction when you're drilling and holds up under heat. Titanium drill bits last longer than standard high speed steel drill bits and have a higher hardness level than cobalt bits. However, the bits cannot be sharpened like cobalt bits as the titanium coating comes off if they're sharpened.
Carbide Drill Bits
Carbide tipped drill bits are strong bits with high heat resistance used for high speed drilling by auto mechanics, locksmiths and machinists drilling into hardened steel. The bits are used to drill out broken bolts and drill bits and to drill into safes and through studs. They are best suited for industrial uses.