What to Know About Cobalt Drill Bits?

Cobalt drill bits can be identified by their color and shape. Cobalt drill bits can be identified by their dull golden color, higher hardness, and less reactivity with the environment. Cobalt drill bits are mainly two types those are M35 and M42. M35 has 5% cobalt included, and M42 has 8% cobalt included. Due to the higher amount of cobalt M42 is harder than M35. Hence M42 is widely used in the production process.

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 bits are not good for resharpening because its coating will be removed due to the sharpening process.

How to Identify the Cobalt Drill Bits?

Cobalt 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 in wet environment.

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 a 135-degree angle.

cobalt drill bit
Cobalt Drill Bit

What are the M35 and M42 Cobalt Drill Bits?

M35 and M42 are cobalt drill bits. M35 contains 5% cobalt with HSS, and M42 contains 8% of cobalt with HSS.

M35 Cobalt Drill Bits

  • M35 drill bits are made from a cobalt alloy containing 5% cobalt.
  • M35 cobalt drill bits have 64-66 HRC hardness value
  • M35 has higher heat resistance and hardness; hence, those are suitable for drilling into tough materials.
  • M35 cobalt drill bits are a cost-effective option for general-purpose drilling in metal and are commonly used in machine shops and for DIY projects.

M42 Cobalt Drill Bits

  • M42 drill bits are made from a cobalt alloy containing 8% cobalt.
  • M42 cobalt drill bits have 68-70 HRC hardness values
  • They offer even greater heat resistance and hardness compared to M35 drill bits.
  • M42 cobalt drill bits are specifically designed for drilling into extremely hard materials, including high-strength steel, stainless steel, and other alloys.
  • They are more durable and have a longer lifespan than M35 drill bits, making them a preferred choice for professional applications where high performance and longevity are essential.

According to the different proportions of the cobalt, physical and chemical properties are varied. Hence, cobalt drill bits are suitable for metals and many hard materials.

What are the 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

  1. TiN – Titanium nitride coating (Golden color coating)
  2. TiCN – Titanium carbon nitride (Grey color coating)
  3. 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.

What is the Durability of Cobalt Drill Bits?

The durability of the cobalt drill bit withstands about 1000-2000 holes of drilling hardened metals such as stainless steel, cast iron etc. However, the durability of the cobalt drill bit can be varied with the hardness of the metal, state of the outer surface, the sharpening and resharpening process, and the melting point and the drilling techniques to be used for the drilling.

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 is 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 be removed, 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. You can use this guide to sharpen the cobalt drill bit step by step.

Is Titanium Drill Bits Better Than Cobalt Drill Bits?

Titanium drill bits are not as good as cobalt drill bits. Because the cobalt drill bit has a higher hardness of 7-8 Mohs scale while it is 6 for the titanium. Although Titanium has a higher melting point of 3034oC it is applied as a coating of the HSS drill bit. Hence its properties are always less than the cobalt drill bits.

Tom Mackency

Tom Mackency

Hi, I am Tom Mackency. It has been 10 years that I have been working as a professional woodworker since 2013. I am really enjoying my carrier by creating many kinds of projects in my workshop. But mostly I like for home improvement projects. Home improvement and DIY projects are the most interesting things for me. More than that, the coolest things are power tools. Those are very precious and efficient than a decade ago. So I try to introduce so many things about power tools, woodworking, DIY projects, home improvement and many more interesting topics here.