When plate and sheet is formed at the mill, it is usually just beginning its fabrication journey. Many different operations can be performed on the material in order for it to serve a specific purpose and provide a value to the end customer. One group of fabrication processes that are often used is known as material removal. Three common types of material removal processes are hole punching, notching, and drilling. While they do have several similarities, they also have many distinct differences that are important to understand when choosing among them.
What are the Differences Between Hole Punching, Notching and Drilling?
In order to understand the differences, we will first discuss what each of these material removal processes involves.
What is Hole Punching?
Hole punching is a shearing process that is used to create holes in material sheet and plate. Hole punching uses hardened tools with sharp edges and an applied force to shear out the unwanted material. The force applied can be electrical, hydraulic, pneumatic, or even manual. The hole punching tools can be a variety of shapes.
What is Notching?
Notching is another process that is used to remove material from sheet or plate. Similar to hole punching, notching is also a shearing process. The use of hardened, sharpened tools are required for notching as well. Notching is different from hole punching, however, when it comes to where the process is performed. While hole punching can occur within the perimeter of a piece of sheet stock or plate, notching is only carried out on the outside boundaries of the material. Notching is primarily used before a subsequent bending or forming operation.
What is Drilling?
Drilling is the only one of these three that is not a shearing process. Drilling removes material through the use of a drill bit. A drill bit is a long, sharp tool, sometimes with flutes in it, although it can have several different features depending on the job type. The drill bit is spun rapidly, and the cutting edges on the bit remove a little volume of material with each revolution as pressure is applied to the drill bit. The force applied to a drill is usually done through a machine known as a drill press; however, it can be done through other machinery as well as hand drills.
Advantages and Limitations of Hole Punching
Hole punching has many advantages over other material removal processes. One key advantage is speed. All types of hole punching presses are relatively fast, but certain types such as servo-driven presses are exceptionally quick. This gives hole punching an even greater advantage in cycle time duration when compared with other hole-creating processes. Another key advantage of hole punching is the different geometries that can be used to create the holes in the material. Since hole punching does not rely on sharp tool rotation, but rather shearing force, the tool does not have to be round. This means that hole punching has the flexibility to create squares, triangles, ovals, and many other shapes.
Hole punching does have its limitations though. Tool wear can have an adverse effect on the process and leave large burrs and poorly shaped holes. Hole punching is also limited in the thickness of material that can be punched. The thickness that can be punched varies depending on material type and the diameter of the hole being punched.
Hole punching is commonly used on high production sheet metal fabrication such as automotive components, airplane bodies, and decorative work.
Advantages and Limitations of Notching
Notching generally has the same pros and cons as hole punching as both processes use presses and rely on shear force to sever the material on which the work is being performed. Notching is fast, and shapes can be varied simply by changing out the notching tool. The same thicknesses that are not ideal for hole punching are also not ideal for notching.
Similar to hole punching, notching is frequently used in sheet metal fabrication. Common applications include those in which sheet metal will be subsequently bent or mechanically formed through other means.
Advantages and Limitations of Drilling
Drilling is quite different than hole punching or notching since it involves cutting through the material by continuously removing layers of materials through a rotating tool with a sharp cutting edge. The finesse of removing layers of material sequentially rather than all at once typically results in a lower amount of part distortion. The equipment to start a drilling operation is generally more affordable than the equipment needed to start a punching operation, especially with thick materials. Additionally, drills can tackle extremely thick materials quite easily, unlike punching or notching tools. Drilling can also perform partial-thickness hole creation.
On the disadvantages side, drilling is limited in geometry. Since it requires rotation to be performed, only circular holes can be created with drilling. Drilling also results in more heat being applied to the material than that of hole punching or notching.
Drilling is commonly used in a wide variety of applications. Since it is a relatively affordable process, many job shops use it for low rate production or maintenance tasks. However, large-scale manufacturing operations may rely on drilling if part distortion is a concern, the material is too thick, or partial-depth holes are desired.
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