Black oxide is used as a finish type (coating) of a drill bit. Cobalt is used as a material for a drill bit. Black oxide is mostly applied on the HSS drill bits in order to improve service life and thermal resistance and reduce the friction between the drill bit and hole surface. Cobalt is a hard and tough material than black oxide. Hence it can be used to drill harder materials which black oxide is not able to use.
Black oxide coating consists of magnetite (Fe3O4) and cobalt drill bits have 5-8% cobalt mixture.
There are more properties and usage. When you use them for your task, you should know them well. So I am going to explain and compare them step by step below. So please keep reading below.
Black Oxide vs. Cobalt Drill Bits Comparison
Black oxide vs. cobalt drill bits are different types of drill bits. Black oxide is a finishing material (coating) for a drill bit and cobalt is a based material for the drill bit. Black oxide is applied to the drill bits in order to improve the thermal resistance and reduce friction between drill bit and hole surface. I have prepared a table to compare the Black Oxide vs. Cobalt Drill Bits quickly.
| Features | Black Oxide Drill Bits | Cobalt Drill Bits |
| Hardness | Harder enough but less than others | Hardest |
| Material Drilled | Metal, wood, plastic | Hard metal |
| Durability | 50% more durability than HSS | Highest |
| Rust resistance | Yes | Yes |
| Re-sharpenable | yes | yes |
| Price | Cheap | Expensive |
You May be Interested to Read About
- Cobalt vs HSS Drill Bits
- Cobalt Vs Titanium Drill Bits
- Black Oxide vs. Titanium Drill Bits
- Black Oxide Vs Cobalt Drill Bits
Black Oxide Drill Bits
Drill bits that are made with black oxide coating can identify as “black oxide drill bits. Those bits are made with a magnetite (Fe3O4) layer coated on the HSS drill bits. The black oxide layer is more important for thermal resistance, heat resistance, and corrosion resistance.
How to Identify the Black Oxide Drill Bits?
Black oxide drill bits are black in color and their price is in the middle range considering other drill bits in the market.
Black Oxide Drill Bit Usage
When we use black oxide as a drill bit all these are important. Additionally, it can increase the life of high-speed steel. When thinking about drilling material, black oxide drill bits are the most versatile. Those are suitable for work on;
- Copper,
- Aluminum,
- Brass,
- Plastic,
- Oak,
- Maple,
- MDF,
- Pine,
- PVC,
- Polycarbonate,
- Acrylic,
- ABS,
- Nylon and composite materials.
Coating Process of Black Oxide Drill Bits
Under the black oxide coating processes, three types of coating processes can be identified. Those are:
- Heat process
- Mid-temperature process
- Cold process.
Those three processes are based on temperature.
HSS heats to 950 degrees of Fahrenheit (oF). This process will help to resist rust and corrosion of the drills because of the friction between the bit and the workpiece will reduce. Therefore, the drilling efficiency and durability of the drill improved.
As well as, friction while drilling will decrease, and it helps speed up the drilling process to a considerable extent. However, black oxide drill bits can be produced by using a cold coating process.
Middle temperature is also used to make black oxide drill bits. Under the cold nature (68–86 °F) true oxide does not produce. It’s like a soft coating. Anybody can scratch the drill bit by using an even coin.
Usage and Durability of Black Oxide Drill Bit
Black oxide drill bits are the best general-purpose drill bits. Those are being cheapest and serve all kinds of purposes. Therefore, black oxide drill bits can be introduced easily for the freshener of the industry. It will be a more efficient step.
Let’s talk about the limitations of the black oxide drill bits. Revolutions per minute (RPM), durability, and sharpening time can be identified as limitations. As previously mentioned, the black oxide coating helps to increase the speed of drilling and the durability of the drill bit.
Black oxide drill bits are fifteen percent more durable than HSS drill bits because those are re-sharpenable drill types. When thinking about affordability, black oxide drill bits are very cheapest than other drill bits.
Cobalt Drill Bits (HSCo)
Cobalt drill bits are not made from pure cobalt. Cobalt drill bits are made from 5-8% of Cobalt alloy with HSS drill bits. This composition helps to give high resistance from rusting. Based on the percentage of the Co in the drill bit, can be identified the different Cobalt drill bits.
How to Identify the Cobalt Drill Bits?
Cobalt drill bits are dark gold in color, and it is not a bright gold color. Bright and shiny gold color drill bits are coated with titanium. Cobalt drill bits are bit more expensive than HSS, Black oxide drill bits.
Types of Cobalt Drill Bits
Among those types of drills, M35 and M42 are the most common Cobalt drill bits. M35 Cobalt drill bits contain approximately 5% cobalt alloy and M42 cobalt drill bits contain approximately 8% cobalt alloy
Physical Properties of the Cobalt Drill Bits
The melting point of Cobalt is 1495°C, and the boiling point is 2927°C. Which makes it perfect for use at high temperatures. The corrosion is cannot identify in the cobalt drill bits. The cobalt drill bit is designed to drill fast. Therefore, this type of drill is suitable for the hardest drilling purposes. Such as cast iron, titanium etc. Cobalt drill bits are exceptionally durable than black oxide drill bits. The toughness of the drill bits affected the durability.
Resharpening of the Cobalt Drill Bit
Cobalt drill bits also can be re-sharpened. Cobalt bits have a uniform concentration of cobalt in their composition. Uniform concentration means the coating process has unique patterns of cobalt moles because cobalt (Co) is the chemical mole in the D block of the periodic table.
The re-coating process cannot rearrange this unique pattern very well. Therefore, cobalt drill bits cannot be re-coated, but they can be sharpened to regain their edge. Cobalt drill bits are very expensive. Cobalt drill bits have a high resistance to heat therefore, those drill bits are suitable for rigid materials.
Black Oxide vs. Cobalt Drill Bits – Conclusion
When concerned about the differences and importance of these two drill bits, the black oxide drill bit is suitable and enough for daily drilling purposes.
Cobalt drill bits can use for professional and industrial valued construction purposes.
If you have to a long period of drilling work unconditionally, you have to use the cobalt drill bits because black drill bits tend to lose their edges very easily than cobalt drill bits when used for the hard material drilling process.
Drill bits can be re-sharpened by using a drill bit sharpener, but a skilled person can use a grinding disc and re-sharper by hand.
The final conclusion is black oxide drill bits are most suitable for regular usage because;
- Reasonably priced,
- Durable ( non-corrosive and can be re-sharpened),
- 50% more durable than regular HSS drill bits,
- Can be used for various purposes,
- Making them the best all-purpose bits.
At first, you have to determine the metal or material type required to drill. Among both of those, cobalt drill bits are the most effective and best drill bit. Although you have to choose a good quality drill bit and use appropriate safety protection.
If in doubt, it is best to drill slowly and use a metal drilling lubricant for better drilling. Take suitable breaks to avoid the drill bit overheating.
Can Black Oxide be Used as a Coating for Cobalt Drill Bits?
Normally, the black oxide coating can be applied on the cobalt drill bits in order to improve the thermal resistance, durability and reduce friction. When the black oxide coating is applied on the cobalt drill bit, it can be used in a wide range with higher performance.
