Drill Bits Material: From Carbon Steel to Diamond

It is important to choose a drill bit made with the right material for your purpose. Getting a softer drill bit than needed will lead to early dullness and uselessness of the tool, leading to endless replacing at best, and a ruined project as one of the sadder scenarios. When picking the material, consider the surface to be drilled into (Soft wood? Hardwood? Metal? Stone?), and the steadiness of the drill itself – a very brittle bit on a cordless drill in the hands of not a very experienced driller is probably not the best idea.

That said, lets consider the standard options:

Low Carbon Steel Drill Bits

This is the cheapest option. Best used only on softwood. Low Carbon Steel bits require frequent sharpening, have a relatively short useful lifespan, and do not hold the edge too well. Buyer beware.

High Carbon Steel Drill Bits

These are an improvement over the above, and can be used on hardwood and even some metals. However their low resistance to heat causes them to loose their sharpness relatively quickly.

High Speed Steel Drill Bits (HSS Drill Bits)

These have essentially replaced the older Carbon steel bits on the market. HSS is significantly more resistant to heat, and as such these bits are well suited to most wood and metal jobs.

Titanium Coated Drill Bits

Titanium coating makes these bits harder and last longer than the common HSS bits. That is because the coating is a hard ceramic material.

There are a number of different Titanium coatings, most common are Titanium Nitride (TiN), Titanium Aluminum Nitride (TiAN) and Titanium Carbon Nitride (TiCN). TiN can increases the life of a drill bit by three or more times. TiAN is considered even better, and can increase the lifespan five times or more. TiCN is also considered superior to TiN.

The problem with coated bits, however, is that once dulled, they can’t be properly sharpened – the coating will be gone, and so will all the benefits of it.

Carbide Tipped Drill Bits

These are very hard, dissipate heat quickly and hold an edge longer than other types. However, Carbide tipped bits are also brittle and are likely to chip if not used carefully.

Cobalt Drill Bits

Cobalt bits retain hardness at much higher temperatures than the HSS ones. However, they are also more brittle than HSS. Cobalt drill bits are most commonly used for drilling stainless steel and other metals.

Diamond Drill Bits

Polycrystalline diamond (PCD) is one of the hardest tool materials. It actually consists of a layer of diamond particles bonded to a carbide support. And since diamond is the hardest thing found in our environment (or at least it is the hardest we know of), the diamond bits can be used on the toughest materials.

Unlike carbide and other types of drill bits, which use sharp edges to cut through material, diamond drills tend to work by grinding away their nemesis on a micro level.

Diamond drill bits can be used on glass, porcelain, ceramic tiles, granite, marble, stone, fiberglass, etc. They are commonly used in the automotive and aerospace industries, and in other environments where abrasive materials need to be drilled.