Drill bits are made with different materials. Among them, steel, HSS, cobalt, carbide, and diamond drill bits are the most used drill bits for any material. Materials have different hardness and strengths. According to this drill bits have been designed to gain the most efficient cutting process.
Normally, each material can line up according to the Rockwell C hardness values. We are not able to drill higher hardness material with lower hardness drill bit material. Due to this reason, drill bits have been manufactured considering each material’s hardness.
So let’s see what the drill bit material, coating, and usage of steel, HSS, cobalt, carbide, and diamond drill bits are?
Most Used Drill Bit Coatings
Drill bits are coated in order to increase friction resistance, heat transfer, and durability. Mostly HSS drill bits are coated with different kinds of materials. When a drill bit is coated, its color has changed. So let’s see what are the coatings and how are they useful?.
1. Black Oxide
Black oxide drill bits are commonly used for drilling into metal, wood, plastic, and other materials. They are typically made from high-speed steel or carbon steel and are available in a variety of sizes and shapes, including twist drills, spade drills, and hole saws.
One advantage of black oxide drill bits is that they are more durable than uncoated drill bits, which can help to extend the life of the bit. They also tend to stay sharper for longer periods of time, which can lead to more accurate and precise drilling.
Advantages of Black Oxide drill bits
- Reduce Friction in the cut
- Reduce heat reduction
- Improve the flow of material
3. TiN (Titanium Nitride)
The Titanium Nitride coating helps to reduce friction and heat build-up during drilling, which can also help to increase the speed of drilling and reduce the risk of the bit breaking or dulling.
Using a TiN drill bit you can drill hard materials such as stainless steel, titanium, and other alloys. TiN-coated drill bits are gold in color and better than black oxide drill bits.
Advantages of TiN drill bits
- Increase higher RPM using this coating
- Better tool lifespan
- Add resistance
- Reduce friction
4. TiCN (Titanium Carbonitride)
TiCN (Titanium Carbonitride) drill bit is a coated drill bit. It can be used to drill hard and abrasive materials such as cast iron, hardened steel, and nickel alloys. TiCN drill bits are ideal for high-speed drilling applications where the bit is subjected to high temperatures and stresses. Normally, TiCN has a longer service life than other drill bit coatings.
Advantages of TiCN drill bits
- Increase hardness
- Add resistance
- Less maintenance
- Longer service life
5. TiALN (Titanium Aluminium Nitride)
Obviously, TiAlN coating has a unique structure that offers superior hardness and resistance to wear, which helps to increase the life of the drill bit. The coating also has excellent thermal stability, allowing the bit to operate at higher speeds and temperatures than other coated bits.
Due to the hardness, TiAlN drill bits have a longer service life than other coatings. TiAlN is a violet-colored drill bit and is specially used for the hardest materials.
Advantages of TiAlN drill bits
- Increase hardness
- It can be used in higher temperatures.
- Lower thermal conductivity than TiN
Drill Bits Coating Characteristics
| TiN | TiCN | ZrN | AlTiN | |
| Hardness (Vickers) | 2300 (81 Rc) | 3000 (87 Rc) | 2500 (85 Rc) | 4500 (90 Rc) |
| Relative Toughness (1=Toughest) | 3 | 1 | 2 | 4 |
| Oxidation Temperature | 550ºC | 400ºC | 600ºC | 800ºC |
| Friction Coefficient | 0.65 | 0.45 | 0.5 | 0.45 |
| Thickness | 2-4 microns | 2-4 microns | 2-4 microns | 2-4 microns |
| Surface Roughness (Ra mm) | 0.2 | 0.17 | 0.2 | 0.15 |
Most Used Drill Bit Materials
1. Steel Drill Bits
Steel drill bits are significant for the softwood, plastic, fiber drilling process. Steel is not a hard material as it can be used for more hard and strong materials. The melting point of the steel is (1375 – 1530°C (2500-2785°F)), and it will melt easily when it is used for drilling to the hard steel material.
Steel drill bits are really easy to sharpen as well as it can be blunt or damage the drill bit tip due to high temperature and resistance. Considering all the factors, steel drill bits are really useful for general purpose.
2. HSS Drill Bits
HSS drill bits are made by mixing the carbon with the steel and chromium, vanadium, tungsten, and molybdenum with different proportions. HSS drill bits are really hard and tough than steel drill bits. HSS drill bits are black colored, and in order to increase the abrasion resistance, and thermal resistance, some special coatings are applied, such as TiCN, and TiN.
HSS drill bits are used to drill some hardwood and some soft steel such as aluminum, brass, etc. hardwoods. If you need to drill cast iron using the HSS drill bit, you can use it successfully. HSS can be easily sharpened, and it has good thermal and wear resistance.
3. Cobalt Drill Bits
Cobalt drill bits are made by adding more percentages of cobalt to the HSS drill bit materials. When 5% cobalt is added to the mixture, it is 5% cobalt, and when 8% is added, it is super cobalt drill bits. 5% cobalt drill bits are introduced as M35 and 8% is named as M42.
Cobalt drill bits can handle 1100 °F temperature and wear resistance. The more percentage of cobalt, is more heat resistance. But a high percentage of cobalt is highly brittle. Hence limited cobalt is mixed with steel and carbon.
Cobalt drill bits can be resharpened without losing their strength. It has a relatively long life span and performs well in the cutting process.
4. Carbide Drill Bits
Carbide drill bits are used to drill hard materials such as concrete, brick, stone, and many hard materials, Those are really resistant to high thrust, heat resistance, and abrasion resistance. Normally carbide drill bits are used in hammer drills. The hammering mechanism is the most effective drilling mechanism into hard materials. Carbide drill bits are made with
- Tungsten Carbide (WC) – Primary carbide component
- Titanium Carbide (TiC) – Added to increase resistance to abrasive wear or cratering of chip-forming surface
- Tantalum Carbide (TaC) – Added to increase resistance to cutting-edge deformation at higher temperatures during heavy cuts
When the carbide drill bit is less sharp, you should replace or resharpen the drill bit. Normally carbide drill bit is not able to sharpen easily with a regular grinder. You have to use a diamond grinder for the carbide bit sharpening.
Read More About – TITANIUM COATINGS
4. Diamond Drill Bits
Diamond Drill Bits are made with powder diamond and coated on steel as a layer. This is a process under 1.5 GPa pressure and 1250 ºC temperature.
Sintered diamond drill bits or burrs – The diamond has been bonded to the matrix at a very high temperature; therefore, several layers of diamonds are dressed on the steel. This will increase the durability and more resistance of the drill bit.
Diamond drill bits are the harder drill bit in the world. So those are used to drill stones, glass, gems, tiles, and many more brittle materials. According to the diamond drill bit production, it is two types.
Electroplated or coated drill bits – Diomand is coated on the steel as a single layer. Then once the layer is wiped due to wear, you have to replace the tool. These are very economical and popular. Single Nickle is used as the bonded layer.
Diamond drill bits can use high thrust and high RPM in the drilling process.
