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Different Types of Drill Bits and Their Application

Updated: Dec 11, 2020

Drill bits are cutting tools on drills, drill presses, and drilling machines. It has a cutting function and is mainly used to remove material from the work piece to make holes. Connect the drill bit to the drill rig. When the power is turned on and the power is generated, the drill bit will be driven by rotation so that the drill bit can create holes in the work piece. The drill bit has a wide range of applications and can be used on machine tools such as drilling machines, lathes, milling machines, and electric drills. The materials used to make drill bits can be divided into high-speed steel (HSS), carbon steel, cobalt steel, and tool steel. There are many different sizes and shapes of drill bits on the market, and many types of holes can be created according to different materials. By choosing the appropriate drill bit, the efficiency of drilling holes in concrete and metal work pieces can be greatly improved.

Drill bits can be roughly divided into flat drill bits, twist drill bits, countersink drill bits, hollow drill bits, center drill bits, deep hole drill bits, and stepped drill bits.


1. Twist Drill Bits

A twist drill bit is the most widely used drilling processing tool, suitable for drilling and cutting on light metal, wood, and plastic work pieces. Usually made of M2 high-speed steel. It is mainly composed of the working part of the drill and the handle. Spiral grooves have 2 grooves, 3 grooves or more, but 2 grooves are the most common. The twist drill bit has two spiral grooves. Decimal sized twist drill bits are usually offered in 1/64 inch increments, with sizes between 1/16" and 1/2". To reduce the friction between the guide part and the wall of a hole during drilling, the twist drill bit will gradually decrease from the drill tip to the shank, so that its diameter will be in the shape of an inverted cone. The helix angle of the twist drill bit will affect the size of the rake angle on the cutting edge, the strength of the blade, and its chip removal performance. The spiral groove can be processed by grinding, milling, hot rolling, or hot extrusion. Due to the structure of the twist drill bit, the rake angle is large at the outer edge and gradually decreases toward the middle. The chisel edge has a negative rake angle (usually up to about -55°), so it will be squeezed during drilling. The role of pressure. Twist drill bits are often used for household use.

In order to improve the cutting performance of twist drill bits, the cutting part can be ground into various shapes according to the nature of the material being processed. The shank of twist drill bits can be divided into two types: taper shank and straight shank. The former is inserted into the taper hole of the spindle or tailstock of the machine tool during processing, while the latter is clamped in the drill chuck. Twist drill bits with welded carbide blades are suitable for processing cast iron and non-metallic materials.

2. Flat Drill Bits

The cutting part of the flat drill bit is a flat spade shape, and the main cutting edge grinds the front angle and the relief angle to form a chisel edge. The flat drill bit has a simple structure, no spiral groove, and low cost, so it is widely used in small hole processing. In terms of structure, flat drill bits can be divided into two types: integral type and assembly type. However, the cutting speed of general flat drill bits is low. Besides, the integral structure is restricted, the working rake angle of the flat drill bit is negative, and the axial force and torque are relatively large. The guiding of the flat drill bit mainly depends on the positioning key on the flat drill chuck, but its guiding is unstable, so it is easy to deviate. The flat drill bit cannot effectively divide the thickness of the cutting layer because the structure of its cutting edge is asymmetric.

3. Countersink Drill Bits

The countersink drill bit is a drill used to countersink taper countersinks. It can process flat, cylindrical, tapered and other profiles on the end face of the hole. Its main function is to process the orifice, deburring, and chamfering the orifice. The premise is that there must be a pilot hole so that it can be processed. Countersink drill bits can be divided into many types of shapes, including cylindrical countersink drills, tapered countersink drills, and inclined hole countersink drill bits. Therefore, according to different needs, we can choose different shapes of countersinks for hole processing. Countersink drill bits are suitable for drilling holes in wood.

4. Hollow Drill Bits

A core drill is a drill bit with a hollow center. It mainly adopts the form of multi-blade ring cutting. The hollow drill bit only cuts the outer ring part of the hole and does not cut the middle part. It is a drill bit used for core drilling. Compared with twist drill bits, hollow drill bits are more efficient and cut faster. The diameter of the borehole ranges from a minimum of 12mm to a maximum of 150mm. And its material can be divided into two main types: one is a high-speed steel drill, the other is a hard alloy steel drill. High-speed steel plate drill bits have good stability and regrind ability; hard alloy steel plate drill bits have higher cutting speeds and can perform drilling operations on complex materials.

5. Center Drill Bits

Center drill bit is often used in mechanical processing and play an important role in the production. It is essentially composed of a twist drill bit with a small helix angle and a counter drill and is mainly used for drilling the center hole of shaft work pieces. The center drill bit can cut briskly and has a better chip removal function. The earliest center drill bit was used in lathes, mainly for drilling the center hole of shaft parts. As the times change, automation is becoming more and more common, so this type of core drill bit is often used in multi-functional numerical control equipment. But its biggest function is to point the center hole to ensure the position accuracy of part hole machining.

6. Deep Hole Drill Bits

The shank of the deep hole drill bit is slender, and it is usually used for drilling deep holes. There are two types of deep hole drill bits: external chip removal and internal chip removal. The disadvantage of deep drilling is difficulty in heat dissipation and chip removal. When deep hole drilling, heat dissipation, and chip removal are difficult, because its drill rod is relatively long and has poor rigidity, so it is prone to bending. Usually need to use a pressure cooling system to solve the difficulty of cooling and chip removal. Besides, because its tool cuts in the hole, it is difficult for us to observe its cutting condition and the degree of tool wear.

7. Stepped Drill Bits

The step drill bit is mainly made of a thin steel plate. The step drill bit can play a role in expanding the hole when drilling. According to the need to process holes of different diameters, the reaming process can be completed at one time without the need to replace any drill bits or drill positioning holes. Step drill bits are often used in plumbing and electrical applications.

In addition to the 7 different types of drill bits we introduced above, there are other drill bits on the market, such as masonry drill bits, auger drill bits, rivet bits, self-feed bits, hole saw, tile bits, hammer bits and etc. If you expect to purchase the drill bits or learn more about drill bits, please contact us at +6011-7000 7687 or email us at

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