In order to drill different materials, we need different kinds of drill bits. So many types of drill bits are available in the market with different performances and prices. Cobalt drill bits are one of them that we can buy from the market. So let’s see, all in detail, about cobalt drill bits.
Cobalt drill bits are made with a combination of steel or another alloy mixed with a small percentage of cobalt. Cobalt has mixed between 5-8% percentages. 5% cobalt include in M35, and 8% is included in M42 cobalt drill bits. These bits are used to drill the hardest materials, such as cast iron.
More than that we should know how to use cobalt drill bits, sharpening, durability, identification including material, and many more. In this guide, you can find all in detail about cobalt drill bits. So let’s keep reading on!
How to Identify the Cobalt Drill Bits?
Drill bits can be identified by their color and shape. Cobalt drill bits can be identified by their dull golden color. It is called an amber surface finish. Cobalt drill bits are not bright golden colors like titanium-coated drill bits. As well as, cobalt drill bits do not rust. Hence you can identify it even wet environment easily.
Cobalt drill bits are harder than the regular HSS (high-speed steel) drill bits and can be sharpened relatively easily with cutting fluid while retaining their strength and durability. The tip has 135 degrees angle.
M35 and M42 Cobalt Drill Bits
Cobalt drill bits are not made from pure cobalt. Cobalt drill bits are a combination of steel or another alloy mixed with a small percentage of cobalt. Cobalt was mixed typically between 5 – 8%. This composition helps to give a high resistance.
Based on the percentage of cobalt in the drill bit, can be identified the different 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. M35 drill bits can be mounted to handheld devices without fear, but M42 drill bits cannot be used as such.
This is because they have a tendency to break higher than M35 drill bits. The melting point of Cobalt is 1495°C, and its boiling point is 2927°C. Suitable for use in high-temperature conditions due to high boiling and melting points.
If something is going to take a long time to drill, these drill bits can be used to get it done in a short amount of time without a lubricant in between. Of course, cobalt drill bits have more attractive features. That ability is due to the mixing of cobalt.
Coated Cobalt Drill Bits
Cobalt drill bits are coated with titanium compounds in order to improve their physical characteristics. Normally, coated cobalt drill bits are different in color. Titanium, Aluminum, Nitrogen, and Carbon are used as the mixed compound layer on the drill bit. The most used coatings are
- TiN – Titanium nitride coating (Golden color coating)
- TiCN – Titanium carbon nitride (Grey color coating)
- TiAlN – Titanium aluminum nitride (Violate color coating)
These coatings are applied on the drill bit in order to improve the service life, and thermal resistance and reduce the friction between the drill bit and the cutting surface.
Usage of Cobalt Drill Bits
Cobalt drill bits are good for metal and wood. Especially it can drill hard metal such as bronze, cast iron, stainless steel, and titanium. Due to the hardness, cobalt drill bits can use to drill welding seams also.
Due to the strength of the cobalt bits and their ability to be used even under high-temperature conditions, these bits can be used for harder metals.
Cobalt bits are not suitable for general applications. Because HSS bits are ideal for completing those tasks at a low cost. So do not use cobalt bits for low-intensity operations such as drilling through wood, plastic or light metal.
When concerned with the drilling of the concrete carbide drill bit is most suitable than the cobalt drill bit because the carbide drill bit is harder than others.
The Durability of Cobalt Drill Bits
Another factor that we all consider when buying a product from the market is its durability. The durability of cobalt and titanium bits was discussed earlier in this article, but we will discuss them further here. The durability of any drill bit depends on
- The hardness of the metal
- State of an outer surface of drill bit
- On the ability and inability to sharpen
- The melting point
Cobalt is an element between “Mohs scale” numbers 7-8 and its means it is a harder metal. And during the production process of cobalt drill bits from HSS drill bits, there has no outer surface painting process. Therefore, it can be sharpened when it becomes blunt. A high level of melting point helps to do the long-period drilling process. In addition, the lifespan of a bit depends on the type of bit used and the drilling technique used.
Can You Sharpen Cobalt Drill Bits?
You can sharpen a cobalt drill bit. When you see, the chip size is less than 2mm, it is time to resharpen the cobalt drill bit. But if your cobalt drill bit has been coated with TiN, TiCN or TiAlN, do not try to re-sharpen it. When you sharpen coated drill bits, their coat will remove, and it will act like normal cobalt drill bits.
If you use blunt bits, the broken part can damage your fingers, eyes and face. Therefore, it is best to sharpen these bits at the appropriate time. Below are the quick steps to resharpen the cobalt drill bits easily.
Simply, the re-sharpening process has a few more steps. Those are;
- Examine the dull bit
- Pick your tool of choice
- Hold the bit correctly
- Cut the landing
- Cut the chisel
- Shape the landing
- Rotate the bit
- Repeat
I use this guide for sharpen the cobalt drill bit in detail
Once you’ve noticed that the bit you are using is blunt, you need to choose which tool to use according to the size to be sharpened. Here the equipment is expensive but an experienced person can sharpen these bits at a low cost. The dull drill bit must keep at 60o angle to the sharpening tool.
Then has to cut the landing and the chisel and has to shape the landing of the drill bit. The full re-sharpening process can be successful by rotating the drill bit and doing a repeated process as mentioned above (Steps 3 to 6).
Titanium Drill Bits vs. Cobalt Drill Bits
Cobalt bits are very easy to sharpen because they have no outer coating.
There is no surface tearing when sharpening them. They have the ability to punch continuously for a long time and ease of sharpening; therefore the lifespan of these bits is long. As mentioned earlier, cobalt bits can be used to make even the most rigid metal drilling process successfully, even at high temperatures.
Titanium bits have an external titanium coating. Over time, during drilling, this coating may peel off. Unlike cobalt bits, titanium has a lower thermal resistance, when this coating is removed; the efficiency of the bits will be reduced. Titanium drill bits are harder than cobalt drill bits, but they will have a shorter lifespan. Before you buy a cobalt drill bit you should know are cobalt drill bits better than titanium?
Is Titanium Drill Bits Better Than Cobalt Drill bits?
| Characteristic | Cobalt Bit | Titanium Bit |
| Atomic number | 27 | 22 |
| Melting point | 2723oC | 3034oC |
| Mohs Scale of Mineral Hardness Rating | 7-8 | 6 |
The most striking difference between cobalt and titanium is their color and appearance. The cobalt drill bits are a dull gold color and titanium bits can identify as HSS bits with brass or orange coloring.
Mohs Hardness Scale is an easy way to identify an element. The hardness of an element or mineral has been identified as a measure of the relative resistance to scratching, and in this concept, the known hardness is derived from scratching against another material. As mentioned in the table above, cobalt has a higher hardness than titanium.
In Conclusion
Cobalt drill bits are essential for both woodworking and metalworking. Due to the hardness of the cable drill bits, it can be used to drill hardened metals such as welding seams. According to the Co mixture, cobalt drill bits are two types. M35 and M42 are them. M35 has 5% cobalt include,d and M42 has 8% cobalt included. Due to the higher amount af coablt M42 is harder than M35.
In order to improve more characteristics, Cobalt drill bits are coated with TiN, TiAlN, and TICN. These coatings’ main purpose is to reduce friction and improve durability and thermal stability. A regular cobalt drill bit can be resharpened easily, and the coated cobalt drill bit is not good for resharpening because its coating will remove due to the sharpening process.
