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Burring, also known as hole flanging, is a sheet metal forming process that creates a raised collar around a punched or drilled hole. This process increases the effective height of the material around the hole, enabling stronger fastening, improved assembly performance, and additional design flexibility.

Burring is widely used in industries such as automotive manufacturing, electronics, industrial equipment, HVAC systems, and precision sheet metal fabrication. It is particularly valuable when creating threaded holes or reinforcement features without increasing material thickness.

This guide explains how burring works, its applications, design considerations, advantages, limitations, and best practices for successful implementation.

Burring is a metal forming process that pulls and forms material around a hole to create a cylindrical collar or flange extending above the sheet surface.

Instead of removing material, the process plastically deforms the metal to create additional wall height around the hole.

The resulting feature can be used for:

• Thread engagement
• Fastener support
• Component positioning
• Structural reinforcement
• Assembly alignment

Burring is commonly performed on sheet metal parts where material thickness alone is insufficient for secure fastening.

The process generally involves two stages:

A pilot hole is first created using:

• Punching
• Piercing
• Drilling
• Laser cutting

The diameter of this initial hole helps determine the final burr shape and height.

A forming tool then stretches and projects the material around the hole upward or downward to create a flange.

The final geometry depends on:

• Material thickness
• Hole diameter
• Forming tool design
• Material ductility
• Required flange height

Proper process control is essential to prevent cracking or deformation.

One of the primary reasons for using burring is to increase thread engagement.

Thin sheet metal often lacks sufficient material thickness for durable threading.

By creating a raised collar, manufacturers can:

• Increase thread depth
• Improve fastener retention
• Enhance joint strength

This may eliminate the need for weld nuts or additional hardware.

Burring allows certain fastening features to be formed directly into the workpiece.

Benefits include:

• Fewer components
• Lower assembly costs
• Simplified production
• Reduced inventory requirements

The flange created during burring adds stiffness around the hole.

This reinforces the surrounding area and helps distribute applied loads more effectively.

Burred holes can assist with:

• Component alignment
• Positioning
• Fastener installation
• Repeatable assembly

This improves overall manufacturing efficiency.

Burred holes are often tapped to create internal threads directly in sheet metal parts.

Applications include:

• Electrical cabinets
• Control panels
• Industrial enclosures
• Machine covers

Automotive manufacturers use burring for:

• Mounting brackets
• Structural assemblies
• Body components
• Fastener locations

The process supports lightweight design while maintaining strength.

Ductwork and ventilation products frequently use burred features for assembly and connection points.

Products such as server racks, communication equipment, and electrical enclosures often incorporate burred holes to improve fastening performance.

The most common type of burring.

Material is drawn outward around the hole to create a cylindrical collar suitable for threading and fastening applications.

Combines a flanged hole with a countersunk profile.

This allows specific fastener types to sit flush while benefiting from increased material thickness.

Used primarily to increase local stiffness and strengthen sheet metal structures around openings.

Burring provides additional thread engagement in thin materials, allowing stronger and more reliable fastener connections.

In many applications, burring eliminates the need for:

• Weld nuts
• Rivet nuts
• Threaded inserts

This reduces both material and assembly costs.

Manufacturers can increase fastening strength without adding thicker material or heavier structural components.

Burring can often be integrated directly into punching or forming operations, improving productivity and reducing secondary processing.

Properly formed burrs improve consistency, strength, and assembly performance across production volumes.

The initial hole size directly affects the quality of the formed flange.

Proper sizing helps:

• Prevent cracking
• Maintain material flow
• Achieve the desired flange height

Incorrect hole dimensions may result in poor forming performance.

Material thickness influences:

• Flange height
• Thread engagement
• Structural integrity

Thicker materials generally allow taller and stronger burrs.

Burred holes should not be placed too close to sheet edges.

Insufficient edge distance may cause:

• Distortion
• Cracking
• Reduced strength

Adequate spacing improves formability and product durability.

Materials with good ductility are generally preferred.

Common materials include:

• Mild steel
• Stainless steel
• Aluminum
• Galvanized steel

Material properties should be evaluated during the design stage.

Cracking may occur when material deformation exceeds its forming capability.

Common causes include:

• Excessive flange height
• Improper tooling
• Low-ductility materials
• Incorrect hole size

Improper process settings can produce deformation around the hole and surrounding surface.

Tool alignment and process control are essential to minimizing distortion.

Variations in material thickness or tooling condition may affect consistency.

Regular inspection and maintenance help maintain stable quality.

Secondary burrs may develop during hole preparation or forming operations.

Additional deburring may be required to achieve final quality standards.

One of the most valuable uses of burring is preparing holes for tapping operations.

Advantages include:

• Increased thread engagement
• Improved pull-out resistance
• More secure fastening
• Reduced need for secondary hardware

For thin sheet metal applications, burring often provides a cost-effective alternative to welded fastening solutions.

Modern manufacturing environments increasingly automate burring processes using:

• CNC turret punch presses
• Servo-electric punching systems
• Automated forming stations
• Robotic handling systems

Automation provides:

• Improved repeatability
• Higher throughput
• Reduced labor requirements
• Better process consistency

Many modern punch presses can perform burring and forming operations in a single setup, reducing production time and material handling.

To achieve reliable results:

• Select appropriate material thickness.
• Use proper pilot hole dimensions.
• Maintain forming tools regularly.
• Verify edge distance requirements.
• Evaluate thread engagement requirements early in design.
• Inspect flange geometry during production.
• Control forming parameters consistently.

Following these practices improves both manufacturability and product performance.

Burring is an important sheet metal forming process that creates raised collars around holes to improve fastening strength, increase thread engagement, and enhance structural performance. By forming material rather than adding hardware, manufacturers can reduce costs, simplify assembly, and improve product quality.

When properly designed and controlled, burring provides a highly efficient solution for creating strong and reliable fastening features in sheet metal components. As automation and advanced forming technologies continue to evolve, burring remains a key process for achieving lightweight, cost-effective, and durable manufactured products.