Cobalt and titanium drill bits are designed for speed and longevity. Cobalt drill bits are made of a solid composition of steel and cobalt; titanium drill bits are made of steel with a thin titanium coating that is harder than cobalt. Although both types are capable and long-lasting, there are a couple of significant differences between them.
Cobalt Drill Bits
Cobalt drill bits are available in two grades. The grades reflect the percentage of cobalt contained within the high-speed steel (HHS) drill bit. An M35 grade cobalt drill bit is 5 per cent cobalt and 95 per cent high-speed steel. M42 grade drill bits have the cobalt content raised to 8 per cent. Like carbide, cobalt is brittle if its concentration is too high.
To distinguish it from a standard HHS drill bit, a cobalt bit is heat-treated to change its colour from steel blue to a shiny gold .
Titanium Drill Bits
The titanium coating is hard and durable if properly used. To extend the life of the titanium coating, it is important to keep the temperature of the bit low and reduce the amount of friction created during the drilling process. Heat is a by-product of drilling. By using heavy pressure and low speed the amount of heat generated will be reduced substantially.
Both cobalt and titanium drill bits can be kept sharp longer by observing proper drilling techniques. When either drill bit is used on metal, reduce the speed at which you drill. Pumping the trigger of the drill will allow the drill bit to cut and keep the revolutions per minute low.
Using a cutting and tapping fluid will keep the drill bit cooler while drilling. The cutting fluid acts as a lubricant between the drill bit and the work piece. This reduction in friction lowers the temperature of the drill bit and keeps the tip of the bit sharper for a longer time.
Effects of Sharpening
This is the one area in which cobalt and titanium drill bits differ. A cobalt drill bit, when properly sharpened will retain the hardness of cobalt. A titanium drill bit will lose the benefit of the titanium coating after it is sharpened. The drill bit will still work, but will dull quickly.
Cobalt and titanium drill bits are both expensive. Cobalt is the pricier of the two. Over the life of the bit, however, the extra initial cost of the cobalt drill bit evens out. Cobalt drill bits can be sharpened many times over and far outlast a titanium coated drill. This means a higher replacement rate for titanium drill bits, which increases their cost over time.