Cobalt bits are a unique type of drill bit, specifically designed to withstand high temperatures. For this reason, cobalt drill bits are preferred when drilling through extremely hard materials, namely metals such as iron, nickel, stainless steel, and titanium. See our titanium vs cobalt drill bits comparison
For the best performance and durability, make sure that you purchase solid cobalt drill bits, and not cobalt coated drill bits. One large advantage of solid cobalt drill bits is their ability to be resharpened several times before having to be discarded. Every time they are resharpened, they perform just as if they were brand new. This is due to the fact that the actual metal being used to make them is cobalt alloy embedded throughout the bit. Drill bits that are merely steel with a cobalt coating will not be so robust. When these are resharpened, unfortunately their performance diminishes quite drastically because the process strips the coating, exposing the inferior metal underneath, and they will then require more frequent resharpening each go around. Solid cobalt drill bits do not have to be resharpened as often and will last much longer.
Certain M ratings will be designated to the various available cobalt drill bits. These ratings wil range between M1 and M56. These ratings refer to the quality, or the percentage of cobalt in which the drill bits are made. The higher the rating number, the higher the quality. For most drilling applications, M35 cobalt drill bits should prove sufficient, as they contain around five percent cobalt. For jobs requiring heavier duty drill bits, M42 drill bits, which contain around eight percent cobalt can be used. M56 cobalt drill bits are the highest quality, and are often used for industrial applications.
It is recommended that you only use cobalt drill bits for their intended use. That is, to drill through very abrasive materials, during which high temperatures are produced, and a standard drill bit will otherwise fail. This is due to cobalt being a brittle metal and applying excess tensile stress to it will cause it to snap. By reserving your cobalt drill bits to these special applications, you will ensure that they will last you several years. To help keep your cobalt drill bits separated from your general use drill bits, most of them will have a distinctive dull gold color.
We also recommend that you purchase split point models.
Split points reduce walking (skidding across the drilling surface), by being able to breach the surface much more quickly, requiring little initial force from the user, therefore also helping to reduce tensile stress.
There is a wide range of purchasing options. You can buy cobalt drill bits individually, which may be a better option if you only do a few specific jobs for the most part, as you would with small handyman applications or with an arts and crafts hobby for example. You can always purchase different types and sizes as you need them. Individually they will cost around $10 – $20 depending on the size, type, and quality of the bit. If you do a wide range of different jobs, as you would with a general contracting business for instance, then buying a set to start out with would probably be better. You can usually find a good set of twenty nine of the most common sizes and types for about $100.