Drill Bits

The drill bits consist of three main parts: the shank, the body, and the drilling point. Twist drills (rotary drill bits) are the most common type of drill bit. They are used for drilling holes in materials such as plastic, wood, and steel. However, they are most often used for metal cutting and are usually made of high-speed steel, also known as HSS.(High Speed Steel)

The shank is the upper cylindrical smooth part of the drill bit used to grip and drive the drill bit. It is tapered to allow easy insertion into the chuck. The upper end of the shank is sometimes flat and is referred to as a tank.

The body of the drill bit is located at the lower end of the drill bit, running from below the shank to the cutting point. It has an upper end with a neck whose diameter is smaller than the section of the body above the neck and the rest of the body. It has several sub-sections, such as the flutes. A flute is a deep groove that often wraps around the bit, providing a way for waste material (chips) to exit the hole.

The point is the sharpened conical end of the drill bit consisting of the side face and the cutting lips. The main cutting edges perform the actual drilling. Although variations are small, long cutting edges outperform short cutting edges in terms of cutting performance.

What materials are drill bits made from?

Carbon steel

Carbon tool steels are used in environments where very little heat is generated. Drill bits are made from low- and high-carbon steel.

High-speed steel (HSS)

Due to its increased hardness and improved wear resistance, high-speed steel (HSS) is a preferred material for use in drill bits. These characteristics allow drilling at higher speeds and through harder materials.

Cobalt

Cobalt High-Speed Steel (HSS) drill bits contain cobalt, which increases the hardness of the material compared to standard HSS.

Carbide

Carbide drill bits are ideal for drilling non-ferrous metals. Carbide drill bits will last 10 or 20 times longer than cobalt drill bits. However, a carbide drill bit can cost almost ten times the price of a cobalt drill bit.

Drill Bit Coatings

Bright Finish

The surface of drill bits with bright finish (shiny gray finish) has no coatings that extend tool life and improve cutting efficiency. Bright finish is the least expensive option and performs well in certain applications.

Black Oxide

Black Oxide (Μαύρο Οξείδιο) is an improvement over bright finish in terms of lubricity. In addition, its additional heat treatment can improve drill bit life by up to 50% compared to conventional HSS. Black Oxide is not a coating but a heat-treatment process used on HSS to reduce friction and wear.

TiN - Titanium nitride

Titanium is a corrosion-resistant metal used as a coating on HSS drill bits to provide extremely high levels of surface hardness in the form of titanium nitride, or TiN. Titanium-coated drill bits can drill difficult materials and last up to six times longer than standard HSS drill bits. You can recognize titanium nitride by its bright gold color.

TiAlN - Titanium aluminum nitride

The titanium-aluminum-nitride (TiAlN) coating is a versatile, general-purpose coating. TiAlN is a chemical compound consisting of titanium, aluminum, and nitrogen. The coating thickness ranges from 1-4 micrometers (m). The coating is resistant to heat and oxidation. This allows higher cutting speeds and a faster working process

Comparison of TIN and TIALN

Different Types of Drill Bits

Choosing the right drill bit can be difficult because there are many possible alternatives.

High-speed steel HSS drill bits

High-speed steel drill bits are the most basic and least expensive general-purpose drill bit. In addition, they can be re-sharpened to extend their service life.

Cobalt Drill Bits

High-speed steel drill bits reinforced with cobalt outperform standard high-speed steel drill bits. In addition, cobalt improves the heat and wear resistance of high-speed steel. Thus, creating a more robust drill bit that is easy to re-sharpen.

Carbide drill bits

On the other hand, carbide is the most expensive but also the most durable. Carbide is a tungsten-carbon compound. Carbide drill bits are usually made of steel with a carbide tip. Carbide drill bits are commonly used for materials that are difficult to drill and for deeper holes. Carbide also allows coolant to pass through holes placed in the drill bit. High-pressure coolant adds lubrication and keeps the cutting zone cool, reducing wear.