Choose the Right Drill Bit – Geometry | Coating | Material

When you drill, you should choose the right drill bit. Materials are with different hardnesses. So you had better select a suitable drill bit for the specific material. It would help if you considered these factors when you select the drill bit for your drilling material.

Normally when you choose the right drill bit you should check its geometry, material, and coatings. Geometry is the shape and cutting angle, the material is about the hardness of the drill bit and coating is values for durability, friction, and thermal resistance.

Drilling is not about only the drill bit. It is a combined process of RPM, drilling mechanism, and drilling machine. If you have selected the right drill bit, you are above the step. So let’s keep reading about how to select a proper drill for your task.

Choose the Right Geometry and Coating for the Drill Bit

Different Types of Drill Bits
Different Types of Drill Bits
Drill Bits with Coatings

Right geometry is the way of cutting and removing method. It is varied with the material. You may see twist bits and spade bits. Those are with different geometry drill bits. And used for different purposes. So many drill bits geometries are available for different tasks. I could find this guide for the drill bit material, coating, and usage in detial.

After the drill bit is made coating is applied. Coatings are with the combined material in order to reduce the friction with tools and materials and increase the heat resistance. Mainly used the Black oxide, Titanium Nitride (TiN), Titanium Carbon Nitride (TiCN), Titanium Aluminium Nitride (TiAlN), and Regular (Bright Finish) as coatings. These coatings will increase durability and add extra protection to the drill bit.

When you choose the drill bit you should select the proper geometry and coating for the drilling process.

Choose the Right Drill Bit Angle

Drill Bit Angles
Drill Bit Angle

135° Bits are intended for hardened materials and cut less aggressively than 118° Drill Bits. 118° bits are used for soft materials such as wood. 118° bits are capable of penetrating steel but the steeper cutting angle will dull quicker

When you select a drill bit these 06 tips will help you. You should have the right drill bit angle. Right drill bit angle permanently removes the cut material in high efficiency, and it is essential for the fast and accurate cutting speed. If your drill bit is dull, you can use this guide to sharpen the drill bit.

And also, the drill bit should not be blunt. If there is no proper angle, it will slipper on the material, and heat is generated highly. This is one of the reasons for drill overheating. So keep the correct drill bit for the material drilling process.

Identify the Material Hardness for Right Drill Bit

Before you start drilling, you should identify the hardness of the material to be drilled. In our day-to-day life, we have to choose drill bits for wood, concrete, plastic, stones, and many more. These are different properties. Among them, we must know, how much strong the material is?.

Normally we can categorize material according to its physical properties. But it is not the perfect way of measuring hardness.

We must know how much hard the material is. The hardness is measured by the Rockwell C Hardness test. It can classify the material hardness according to its hardness. If the material is harder, it will have more HRC value, and less hard there will be less valuable. By using these values, you can find the related drill bit.

If we need something, we need equal or more hardness material than that. So hardness values are real data for the drilling material and observation of the hardness.

Read More About – About Rockwell Hardness Test

MaterialRockwell Hardness Material Rockwell Hardness
Non-alloyed structural
HRB 62Diamond1600
Non-alloyed structural
HRC 21Tungston+carbide66-68 HRC
Sheet steelHRC 22Stone 89 HRC
Non-alloyed tool steelHRC 22 Cast steel HRC 34
Alloyed tool steelHRC 26 Malleable cast iron HRC 95
Alloyed tool steelHRC 31 Cast iron HRC 22
Stainless steelHRB 85 Spring steel HRC 34
Stainless steelHRC 34
Rockwell C Hardness Values for Materials

Read More About – 06 Tips to Select the Right Drill Bit

Type of Drill BitMaximum HRCCan DrillCan’t Drill
Hi-Molybdenum HSS Drill Bit54 HRCMild steel, tool steel, spring steelHard plate, anti-drill plate, stainless steel, spring steel
Cobalt HSS Drill Bit58 HRCMild steel, spring steel, tool steel, stainless steelHard plate, anti-drill plate, hardened stainless steel
Carbide-Tipped Drill Bit70+ HRC Any steel, ceramics, brick,
Solid Carbide Drill Bit70+ HRC Any steel, ceramics, brick,
Carbide Matrix GSA container hard plate, as this fragile edge, will be destroyed
Diamond-Coated Twist Drill Bit50 HRC Mild steel, some tool steel, some spring steelhard plate, anti-drill plate, hardened stainless steel
Diamond-Core Drill Bit70+ HRC Cast iron, Carbide Matrix GSA container hard platemild steel, spring steel, stainless steel, hardened stainless steel
Rockwell C Hardness Values for Drill Bits

Choose the Right Drilling Machine for the Right Drill Bit

The drilling machine is the essential tool in this process. There are types of drilling machines available in the market. When you choose the right drill machine you can see each one has been defined for a specific task. Regular spinning is a common task of the drilling machine. By adding unique mechanisms to the drill bit, its application can be changed.

When the drill bit is moving with the chuck-it is called a hammer drill. There is a slight difference between a hammer drill and a regular drill. Hammer drills are essential for the hard drilling process, such as concrete, brick, and stones. When the drill bit is moving forward and backward inner material can be crushed into small pieces, and it will remove from the flutes of the drill bit. This is a really helpful method to drill into the hard materials.

Some time drill bit is moved with more power than the chuck. These are called the SDS drills. SDS drills are with high hammering power, and it is used for heavy-duty jobs.

Cordless drills, corded drills, bench drills, and many more types of drilling machines are available in the market. For the DIYs, Cordless drills are really helpful for outdoor usage and corded drills are useful for continuous heavy-duty projects, and bench drills can be considered as a permanent drilling solution. So when you select a drill, categorize the necessity and the most suitable drill.

Choose the Right Drill RPM for Drill Bit

Drill Bit size and Speed
Drill Bit size and Speed (Download Printable Version)

Drill bits are made with different materials. Those are used to drill various materials. Drilling should be done with the recommended RPMs. When the RPM is high, you can see, that the drill bit is hot due to these reasons. I could manage to cool the drill bit using these 09 tips easily.

For wood and plastics, you can use high RPM such as 2000-3000, and for hard materials such as steel, stone, bricks, and concrete, you should use low RPM. Most drills are with different speeds. In this situation, RPM can be changed and according to that torque is varied. When the a high RPM, there will be less torque, and low RPM will have high torque. So You should know the torque and RPM before you drill the material.

Choose the Right Drilling Mechanism

Drill machines are with different drill mechanisms. Hammer function, impact function, and regular drilling function are them. All these processes are in most hand drills. Bench drills are consist with just spinning. When you drill, you should know which function should you activate for the drilling. If you drill concrete, you can start the hammer function with a carbide-tipped drill bit. This hammer function can be activated in wood using a wood drill bit. Wood will be cracked easily due to hammer function.

Currently, most drills are with impact, hammer, and spinning functions together. These drills are called combi drills. When you use a combined drill you should know which function is activated for the related drill bit and material.

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.