All About Knurling in Manufacturing: Processes, Tools & Applications

Have you ever picked up a tool and noticed those diamond-shaped patterns on the handle? That’s knurling – a manufacturing process that creates patterns on metal surfaces. Knurling helps make parts easier to grip and adds style to finished products. In this guide, we’ll explore everything you need to know about knurling in manufacturing.

What Is Knurling?

Knurling is a manufacturing process that creates a pattern of straight, angled or crossed lines on a workpiece. The main reasons manufacturers use knurling include:

• Making surfaces easier to grip
• Adding decorative patterns
• Creating press-fit connections between parts
• Preventing slipping in high-use items

Knurling shows up in many fields including aerospace, automotive, electronics, and marine industries. You can see knurling on everyday items like:

• Barbell handles at the gym
• Metal parts of pens
• Camera adjustment rings
• Guitar tuning pegs
• Medical tools

How Knurling Works

The Knurling Process

The basic knurling process happens in four main steps:

1. Material selection – Choosing the right metal (usually aluminum, brass, or mild steel)
2. Tool setup – Mounting the knurling tool on a lathe or CNC machine
3. Pattern imprinting – Pressing the knurling wheel against the spinning workpiece
4. Finishing – Sometimes adding extra treatments like anodizing or plating

For good knurling results, manufacturers must pay close attention to:

• Feed rate – How fast the tool moves across the workpiece
• Pressure – How hard the tool presses against the metal
• Alignment – Making sure patterns line up correctly

Materials for Knurling

Not all materials work equally well for knurling. According to research data, about 80% of knurling applications use aluminum, brass, or mild steel, with about 15% using plastics.

The best materials for knurling are:

Very hard materials like hardened steel or titanium can be knurled, but they need special tools and techniques. When materials are too hard, the knurling may not form properly or might damage the tools.

Types of Knurling Processes

Cut Knurling vs. Form Knurling

There are two main ways to create knurls:

Form Knurling:

• Pushes material into new shapes without removing it
• Creates raised patterns
• Works best on softer metals (under 30 HRC hardness)
• Uses less force but needs softer materials

Cut Knurling:

• Actually cuts into the material, removing tiny bits
• Creates deeper, sharper patterns
• Works on harder metals (over 30 HRC hardness)
• Needs more force but can work on tougher materials

Cut knurling will actually make the part’s diameter slightly smaller, while form knurling might make it slightly larger as material gets displaced.

Common Knurl Patterns

Knurling comes in several pattern types:

• Straight – Parallel lines running around the part
• Diagonal – Angled lines in one direction
• Diamond – Crossing diagonal lines creating diamond shapes
• Cross – Straight lines crossing each other
• Convex/Concave – Patterns that curve in or out

The diamond pattern is most common because it provides the best grip. According to ANSI B94.6 standards, about 90% of manufacturers follow these specs for consistent sizing.

Knurling Tools & Equipment

Tool Types

Several kinds of tools can create knurls:

• Scissor-type holders – Have two wheels that press from opposite sides
• Straddle knurling tools – Single wheel that presses against the work
• Two-wheel tools – Create patterns with two wheels working together
• CNC-compatible knurls – Made for computer-controlled machines

These tools vary in cost from $50 for basic two-wheel tools up to $1,000 for advanced CNC-compatible models.

Machine Integration

Knurling happens on two main types of machines:

1. Lathes – The workpiece spins while knurling tools press against it
2. CNC milling centers – Computer-controlled machines that can create more complex patterns

For the best results on a lathe, speeds between 50-200 RPM work best with feed rates around 0.1-0.3 mm per revolution.

Want to learn more about how CNC milling works with knurling? Check out our detailed guide to CNC milling for more information.

Applications of Knurling

Functional Uses

Knurling serves many practical purposes:

• Grip enhancement – Makes tools, handles, and controls easier to hold
• Press-fit joints – Creates friction for joining parts without fasteners
• Surface adhesion – Helps glue or other materials stick better

A case study from the automotive industry shows how diamond knurling with 40 TPI (teeth per inch) pitch on aluminum gearsticks resulted in 30% faster assembly and reduced wear over time.

Similarly, in aerospace applications, helical knurling on titanium fasteners created connections 50% stronger than untreated surfaces.

Aesthetic & Industrial Uses

Beyond practical functions, knurling serves design purposes:

• Decorative finishes on consumer goods like watches, pens, and cameras
• Visual indicators showing where to grip or adjust
• Brand identification through unique knurl patterns

High-precision aerospace and automotive components often use knurling where exacting tolerances are needed. For example, our titanium CNC machining services often incorporate knurling for critical aerospace components.

Best Practices & Troubleshooting

Avoiding Common Defects

Common problems with knurling include:

• Double-tracking – When patterns don’t align, creating messy results
• Chip buildup – Material getting stuck in the pattern during creation
• Misaligned patterns – Uneven or off-center designs

According to manufacturing data, misaligned patterns account for 60% of all knurling defects. To fix this:

• Make sure your tool is properly aligned
• Start with light pressure and increase gradually
• Use the right speed for your material

Optimizing Results

For the best knurling results:

• Use lubricant – Especially for form knurling to reduce friction
• Adjust speed/feed – Slower speeds often give cleaner patterns
• Maintain tools – Keep knurling wheels sharp and clean
• Match pattern to purpose – Use diamond for grip, straight for decoration

If you’re working with aluminum, our guide to aluminum CNC machining provides more specific tips for getting great results.

Advanced Knurling Techniques

Micro-Knurling

For medical devices and precision instruments, micro-knurling creates tiny patterns that are:

• Less than 0.5mm in pattern size
• Often created with special CNC equipment
• Used on surgical tools and small electronic components

Multi-Pattern Knurling

Some advanced applications use:

• Different patterns on the same part
• Varying depths of knurling
• Transitions between knurled and smooth surfaces

These techniques require advanced 5-axis machining equipment for precise control.

FAQs About Knurling

Conclusion

Knurling may seem simple, but it’s a versatile manufacturing process that combines function and style. From helping you grip your barbell at the gym to ensuring critical aerospace components fit together perfectly, knurling plays a key role in modern manufacturing.

Whether you’re designing a product that needs knurling or just curious about those diamond patterns on your tools, understanding the basics of knurling helps you appreciate this important manufacturing technique.

For more information on manufacturing processes that often include knurling, check out our guides to CNC turning and precision CNC machining.