What are Drill Bits: Types, Materials & Selection

Few tools are as fundamental to machining and fabrication as the drill bit. Whether you're drilling a simple clearance hole or working through hardened steel on a production line, the right drill bit can mean the difference between a clean, accurate hole and a ruined workpiece or a snapped tool. With so many types, materials, and coatings available, understanding what separates one drill bit from another makes it much easier to choose correctly for the job at hand. 

What Is a Drill Bit? 

A drill bit is a rotary cutting tool used to create round holes in a workpiece. Most drill bits share the same basic anatomy: a cutting point at the tip, spiral flutes that run along the body to clear away chips, and a shank that fits into a drill chuck or tool holder. While the concept is simple, the details, length, material, coating, and point geometry, all affect how a drill bit performs in each application. 

Common Types of Drill Bits 

Twist Drills 

The twist drill is the most recognizable and widely used drill bit design, featuring helical flutes that spiral around the body to evacuate chips as the bit cuts. Twist drills come in several standard lengths, each suited to different applications. 

Jobber Drills 

Jobber drills are the standard, general-purpose length of twist drill, falling between the shorter stub-length drills and the longer taper-length drills. Because of their balanced length-to-diameter ratio, jobber drills are the go-to choice for most everyday drilling tasks, offering a practical mix of reach and rigidity. It is widely sued in machining applications. 

Stub (Screw Machine) Length Drills 

Shorter and more rigid than jobber drills, stub length drills resist deflection and walking, making them a good choice for tougher materials or situations where extra stiffness is needed, such as on screw machines and lathes. 

Taper Length Drills 

Taper length drills have longer flutes and shanks than jobber drills, allowing them to reach deeper holes. Their extended length does require more care to avoid deflection, especially in harder materials. 

Drill Bit Materials 

The material a drill bit is made from has a major impact on its durability, heat resistance, and the type of material it can effectively cut. 

High-Speed Steel (HSS) 

HSS is the most common and cost-effective drill bit material, offering good performance across a wide range of general-purpose drilling applications in wood, plastic, and softer metals. 

Cobalt 

Cobalt drill bits (often designated M35 or M42) contain added cobalt content, which increases heat resistance and hardness compared to standard HSS. This makes them well-suited for drilling harder metals, including stainless steel and other tough alloys. 

Carbide 

Carbide drill bits are significantly harder than HSS or cobalt, allowing them to hold a sharp edge at high speeds and in abrasive materials. They're commonly used in high-volume production environments, though their added hardness also makes them more brittle and prone to chipping if not used correctly. 

Coatings That Improve Performance 

Many drill bits are coated to reduce friction, improve heat resistance, and extend tool life. 

• Black oxide provides mild corrosion resistance and reduced friction at a low cost. 

• Titanium Nitride (TiN) adds surface hardness and reduces friction, extending tool life in general-purpose applications. 

• Titanium Carbonitride (TiCN) offers greater hardness than TiN, making it a good choice for more abrasive materials. 

• Titanium Aluminum Nitride (TiAlN) is designed for high-heat applications, helping the bit maintain its edge at elevated drilling temperatures. 

Point Angles and Geometry 

The angle of a drill bit's tip affects how it cuts and centres itself in the material. 

• 118° point angle is the standard, general-purpose angle, well-suited to softer materials like wood, Aluminium, and mild steel. 

• 135° split point is designed for harder materials, reducing walking and improving self-centring, which is especially useful when starting a hole without a pilot mark. 

Choosing the Right Drill Bit 

Selecting the right drill bit comes down to matching the tool to the material, hole depth, and production requirements: 

• For general-purpose drilling, a standard HSS jobber drill is usually the right starting point. 

• For harder metals or high-heat applications, cobalt or coated bits offer better durability. 

• For deep holes, taper length drills provide the reach needed without excessive flexing. 

• For rigidity in tough materials, stub length drills reduce the risk of deflection. 

For shops and workspaces that need a versatile mix of sizes on hand, a quality set of drill bit sets is often the most practical solution, providing a range of diameters ready for whatever job comes up next. 

Conclusion 

Drill bits may look simple, but small differences in type, material, coating, and geometry can make a significant difference in performance, tool life, and hole quality. Understanding these distinctions makes it easier to choose the right bit for the material and application at hand, helping to avoid premature wear, poor hole finish, or unnecessary tool breakage on the job. 

HVH Industrial Solutions is an authorized distributor of Destiny Tool, and Champion Cutting Tool, and we offer a wide selection of their drill bits. We work closely with their engineering team to provide superior customer service and engineering support.

If you have any questions, write to us via live chat or call or send us a quote request. Our team is always ready to help you.

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