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Drilling

Updated: Nov 6, 2023

drilling, boring, drill
Figure 1: Drill

Drilling is a cutting process in machining technology in which a rotating cutting movement is used as the main movement. During drilling, the material is processed through a combination of rotational and axial movement of the drill or drilling tool. The rotation of the drill creates a rotary cutting motion that cuts and removes the material, while the axial motion inserts the drill into the workpiece and creates the hole.

The rotational movement of the drill allows material to be removed from the workpiece surface and to create the hole of the desired shape and size. During the drilling process, the drill generates cutting forces that remove material. The combination of rotational and axial movement allows precise placement of the hole and control over its depth.

Drilling is used in various applications, from making holes in metal, wood, and plastic workpieces to making threads and other machined features. The choice of the appropriate drill, cutting speed, feed and other parameters depends on various factors, including material, hole size and desired surface finish.

The action of a twist drill is essentially a combination of rotation and axial movement, allowing the drill to remove material from the workpiece surface and drill holes. The twist drill is clamped into a drill or other suitable drilling tool. The tool gives the twist drill a rotational movement around its longitudinal axis. This rotation allows the drill's cutting edges to cut into the workpiece.

During the drilling process, the twist drill is inserted into the workpiece. This occurs through a simultaneous axial movement controlled by the drill or drilling tool. The combination of rotation and axial movement causes the drill to gradually move into the workpiece and remove material. The cutting edges at the tip of the twist drill are designed to penetrate the workpiece and cut material. As the drill rotates and advances axially, the cutting edges cut the material in small increments, creating chips. The chips generated during drilling are usually removed through the spiral-shaped worm or flutes on the drill. These grooves serve to transport the chips out of the hole and prevent blockages from forming.


Drilling processes


There are various drilling processes (Figure 2) in machining technology that are used depending on the specific requirements, the workpiece material and the desired machining quality.

drilling, boring, drill
Figure 2: Illustration of different drilling processes

Here are some common drilling methods:

Drilling: Drilling is the most commonly used drilling method. This uses a twist drill that moves into the workpiece through rotation and axial movement to drill a hole. This process is versatile and is used for a wide range of materials and applications.

Reaming: Reaming is a machining process in which an existing borehole is enlarged. This may be necessary to bring the hole to the desired size or tolerance or to achieve a specific surface finish. Reaming typically occurs after a center hole or pilot hole is created to set the starting point for drilling.

Countersinking: Countersinking is a process in which a tool is used to create a tapered depression at the bottom of an existing hole. This is used to countersink screw heads or other fasteners.

Centering: Centering drilling, also known as centering or center hole drilling, is a drilling process that is used to create a precise starting point for subsequent drilling or machining steps in workpieces.

Core drilling: Core drilling, also known as hollow drilling, is a special drilling process in which larger holes are drilled in workpieces, especially metal, concrete, masonry and other hard materials. Unlike traditional drilling, which removes material from the workpiece, coring creates a cylindrical core (coring core) while removing the excess material from the hole as chips.

Tapping: Tapping is a machining process in which a thread is cut into a workpiece, usually into an already existing hole. These threads are used to hold screws, bolts or other fasteners and create a secure connection. Tapping is an important step in metal processing used in various applications.

Reaming: Reaming is a precision machining process that uses a reamer or reaming tool to refine the surface of an existing hole and achieve the exact tolerance and surface finish.

Selecting the correct drilling method, drill bit and cutting conditions depends on the specific requirements of the project and the workpiece material. The precision, accuracy and surface finish of the holes are crucial to ensure that the manufactured products meet the requirements. Drilling is a versatile technique and plays a critical role in many different manufacturing processes and industries.


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