Sheet Metal Shearing Explained: Types, Principles, and Cutting Methods

Shearing is a foundational process in sheet metal fabrication, enabling fast, chipless cutting of metals into specific shapes. Whether you’re a tradesperson, technician, or beginner learning metalworking, understanding how shearing works, what machines are used, and how to stay safe is essential.

In this article, we’ll walk you through the purpose, benefits, tools, operations, and safety procedures of shearing.

1.0What Is Shearing in Metalworking?

Shearing is a non-chip cutting method for sheet metals and steel sections. It produces straight or curved cuts in selectable lengths without removing material.

Advantages of shearing over sawing or chiseling:

• No material loss during cutting
• Precise alignment along scribed lines
• Minimal finishing required on cut surfaces
• Faster cutting speed
• Straight or curved cutting paths

Common shearing techniques include:

• Cutting-in
• Cutting-off
• Cutting-out
• Punching

2.0Types of Shearing Tools and Machines

Different tools are used for shearing based on material thickness and cutting style. Below are the most common types of shears:

2.1Tinners’ Snip

Used for short straight or curved cuts on thin sheet metals.
Max cutting thickness:

• Steel – 0.7 mm
• Brass – 0.8 mm
• Copper – 1.0 mm
• Aluminum – 1.0 to 2.5 mm

2.2Tinners’ Through Snip

Designed for longer straight cuts in thin sheets. Material passes under the hand for safety.

2.3Hole Cutting Shear

Used for curved cuts in thin metal. The one-sided curved blade is not suitable for straight cuts.

2.4Curve Shear

Ideal for circular or curved cuts in thin to medium-thick sheets up to 4 mm. The sheet can be rotated during cutting.

2.5Guillotine Machine

Used for straight cuts of thin sheets (~3 mm) over long lengths. The top blade strokes downward against the lower blade. Available in manual and powered models.

2.6Lever Shear

Performs short straight or curved cuts in medium-thick sheet metal or steel sections. The upper blade pivots downward through a lever transmission. A locking device prevents unintended blade movement.

2.7Circular Shear (Roller Shear)

Used for long curved cuts in thin or thick sheets. Features rotating wheel-shaped blades. For thick materials, multiple passes may be needed.

2.8Electric Tinners’ Snip

Used to cut thin sheets with curved paths. The upper blade moves rapidly up and down via motor, while the operator guides the sheet.

2.9Cutting Tools (Punch and Die)

Used for repeated, identical cuts in production. The punch fits precisely into the cutting plate with a clearance of 0.05 to 0.1 mm based on sheet thickness.

Recommended Reading:Punch Failure Troubleshooting: Alignment, Clearance, and Safety Tips

2.10Power-Driven Shear Machine

For very long or thick sheet metal (over 10 mm) and strong sections. Features include a powerful drive, hydraulic hold-down bar, and blade gap adjustment.

3.0Construction and Working Principles of Shears

Shears are built to withstand high cutting forces. Key technical considerations include:

• Blade wedge angle: approx. 80°, for stability
• Clearance angle: 2°–3°, reduces friction
• Blade gap: 0.05–0.1 mm × sheet thickness, to ensure clean cuts

Improper blade gap can lead to uneven edges or bent sheets.

Excessive gap leads to poor surface finish and sheet deformation.

Use of a properly adjusted hold-down bar prevents sheet movement.

Parallel blades shear the entire edge at once, requiring more force. Most machines use an inclined top blade to reduce the required cutting force.

Feeding the workpiece deeply into the shear increases leverage, but also increases the risk of workpiece slippage. The blade rake angle (~15°) is necessary to maintain cutting quality.

4.0The Shearing Process: Step-by-Step Operation

The shearing process consists of three key stages:

4.1Notching

Initial indentation of material as the blades contact the sheet.

4.2Cutting

Blades penetrate and break through the metal structure.

4.3Tearing

Final separation of the material due to internal tension and tearing.

These stages leave identifiable zones on thick-sheet cut faces.

5.0Shearing Techniques: Cutting Methods and Their Use

Shearing can be classified by the type and extent of material separation:

5.1Cutting-In

Partial depth cuts are used to prepare the sheet for subsequent bending or folding operations. The cut does not go entirely through the material but weakens it along a line to allow precise and controlled deformation.

5.2Cutting-Off

A complete through-cut that separates the workpiece into two sections, usually to remove unwanted material as scrap. It is a basic shearing action performed using hand or machine shears.

5.3Cutting-Out

This technique involves cutting along a closed contour, such as a circle or rectangle, where the inner portion is the desired workpiece and the outer portion is discarded. It is commonly used to extract functional shapes from sheet material.

5.4Punching

Similar to cutting-out, punching also follows a closed-line path. However, in punching, the removed inner section is considered waste, and the remaining surrounding sheet forms the actual workpiece. This is one of the most common operations in industrial sheet processing.

5.5Integrated Pressing in Modern Manufacturing

In modern fabrication processes, press machines are capable of performing all the above shearing techniques—cutting-in, cutting-off, cutting-out, and punching—using customized punch and die sets. These machines are commonly found in progressive die stamping, hydraulic presses, y C-frame presses used in mass production.

Press machines offer:

• High repeatability and consistency
• Reduced cycle times
• Complex multi-stage cutting in one stroke
• Integration with feeding and automation systems

This integration has made them essential tools in sectors such as automotive, appliance, and electronics manufacturing.

6.0Operating Procedures: Performing Shearing Tasks

6.1Cutting-In with Tinners’ Snip

• Mark the sheet accurately
• Open jaws at approx. 15°, align with the line
• Partially close the snip, avoid tearing
• Progress step-by-step to full length

6.2Cutting-Off with Lever Shear

• Mark and align the sheet
• Adjust blade clearance if needed
• Engage the hold-down bar and unlock lever
• Lower the blade smoothly, avoid a full stroke to prevent cracking
• Lock the lever after cutting, and remove the scrap

Always place the scrap side to the right of your line of sight.

6.3Cutting-Off Angle Sections with Lever Shear

• Mark the inside surface
• Insert into the profiled section the blade holder
• Align with cutting-edge
• Unlock and pull the lever down with force
• Discard waste immediately

7.0Safety Guidelines for Shearing Operations

• Wear gloves when handling sheet metal
• Keep your hands clear of the blade area
• Use only properly maintained tools
• Secure the hand levers after cutting
• Use section knives for structural profiles
• Follow all instructions from the equipment manufacturers
• Dispose of bent or sharp scrap immediately to avoid injury

8.0Frequently Asked Questions

What happens if the blade clearance is too wide?
Poor surface quality, burrs, and sheet bending.

Why is the blade wedge angle so large?
To ensure the stability and durability of the cutting edge.

What is the difference between cutting out and punching?
In cutting out, the inner piece is kept; in punching, the inner piece is waste.

Why is a 15° rake angle important?
It lowers the required cutting force and improves cutting quality.

Why must structural sections be cut with section knives?
Flat blades may chip or break when cutting solid sections.

9.0Conclusion

Shearing is a fast, efficient, and reliable method for processing sheet metal and steel sections. Mastery of tool selection, machine adjustment, and safety procedures ensures quality results and reduces risk in metal fabrication.