What Is Shear Cutting? Process and Technique Overview
Shear cutting—also known as shearing—is a fast and efficient method for cutting sheet materials like metal, plastic without generating heat or chips. Commonly used in industrial fabrication, it’s especially suited for slicing large coils or fixed-length sheets into more manageable sizes. In this article, we’ll explore how shear cutting works, compare the different types of shearing machines, and highlight the key benefits of this clean, cost-effective cutting method.
What Is Shear Cutting?
Shear cutting is a type of mechanical shearing process in which material is cut using parallel blades. The process relies on shear force — a force that acts in opposite directions, causing material to deform and ultimately fracture along the cutting line.
For example, when a rod is fixed to a wall and pulled downwards, it experiences downward force at the free end and upward reactive force at the fixed end. This opposing force is called shear stress. In materials such as metal, which have plasticity, applying shear force first causes plastic deformation, followed by fracture and separation. Shearing utilises this principle to achieve a clean cut.
Scissors are a familiar example of shear cutting. Even safety scissors with plastic blades can cut paper by applying shear force between the two blades.
Shearing is used across many industries — from metalworking and sheet metal processing to cutting materials plastic sheets. Unlike laser cutting or stamping, which are used to create complex shapes, shearing is typically used to cut larger stock materials, such as coils or standard-size sheets, into smaller, manageable sizes before further processing.
How Shear Cutting Works
The shearcutting mechanism is similar to that of scissors. When cutting with scissors, we instinctively hold the lower blade steady and move the upper blade to create the cut. Shearing machines work in the same way: a fixed lower blade (die) supports the material, while a moving upper blade (punch) performs the cutting motion.
The angle at which the upper blade meets the material is called the shear angle. Thin sheets require a smaller shear angle, while thicker materials need a steeper angle. If cutting defects occur, adjustments to the shear angle can help — but reducing it too much may cause material deformation. Likewise, an excessively large shear angle can also lead to issues. The optimal blade clearance depends on the thickness of the material and must be adjusted accordingly.
Types of Shearing Machines
Shearing machines — also known as sheet metal guillotines, power shears, or shear presses — are available in various types. Among them, two are most commonly used in industry:
1. Mechanical Shearing Machines
Mechanical shears use motorised power and a flywheel-driven clutch system to move the upper blade. These machines are simple in structure, making them easy to maintain, and they offer high-speed processing. However, they produce a strong cutting shock and are generally not suitable for thicker materials. As a rule of thumb, mechanical shears struggle with metal sheets thicker than 6 mm.
2. Hydraulic Shearing Machines
Hydraulic shears operate by driving the upper blade using a hydraulic pump system. They offer stable cutting performance, regardless of the material’s resistance, making them suitable for thicker metal sheets over 6 mm. Hydraulic shears also generate less vibration and shock during operation. However, they are slower than mechanical shears and require regular maintenance of hydraulic components.
What Are Burrs and Distortion in Shear Cutting?
When using shear cutting, two surface defects can occur: burrs and distortion.
- Distortion occurs when the upper blade pushes and deforms the material during cutting. This results in a rounded or tapered edge in the cutting direction.
- Burrs are sharp protrusions formed as the material is torn away by the shear force. Burrs are common in many machining processes and can interfere with assembly or pose safety risks to operators and users.
To ensure safe and accurate parts, deburring is essential. This can be done using abrasive tools, grinding, or dedicated deburring machines.
The precision of the shearing equipment and the clearance between upper and lower blades have a major impact on the size and severity of burrs and distortion.
Advantages of Shear Cutting
Compared with other cutting methods such as laser cutting, flame cutting, grinding or sawing, shear cutting offers the following benefits:
- No chips or swarf: Unlike sawing or milling, shearing generates no cutting waste.
- Minimal material loss: Because it doesn’t produce offcuts or scrap (like blanking does), it makes efficient use of material.
- No heat-affected zones: Shearing is a cold-cutting method, so the material’s properties remain unchanged.
- Eco-friendly: Reduced waste and no need for cooling agents make it a sustainable choice.
- Ideal for continuous production: Fast and consistent processing is suitable for large-batch manufacturing.
- Clean cut surfaces: Blades provide a smooth edge finish, often requiring minimal post-processing.
- High-speed operation: Particularly in thin-gauge sheet processing.
Shearing is best suited for cutting large sheets into smaller blanks before further fabrication. Companies can reduce material costs by purchasing coils or standard-length stock and shearing it in-house, rather than buying pre-cut blanks.
Conclusion
Shearing (or shear cutting) is a mechanical cutting method that uses opposing blades to apply shear force to a material, separating it without heat or chips. It’s widely used for cutting metals, plastics, and paper sheets, and works on the same principle as scissors.
The two main types of shearing machines — mechanical and hydraulic — each have their advantages depending on material thickness. While mechanical shears are fast and cost-efficient, hydraulic shears are more suitable for heavy-duty applications.
Shearing may produce burrs and surface distortion due to the material’s plastic deformation, but proper adjustment and post-processing can manage these defects.
Thanks to its efficiency, clean cuts, and minimal waste, shearing remains a cost-effective and environmentally friendly method in modern sheet metal processing.
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