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Knurling is a metalworking process that involves cutting small, raised patterns into the material’s surface to improve grip and aesthetic—often both. Depending on the application and the complexity of the work, there are several different types of knurling. In this post, we’ll discuss different types of knurling, different knurling methods, and the advantages and drawbacks associated with each type.

Types of Knurling Patterns

Though knurling improves the grip and aesthetic of a component that it’s being applied to, different knurl patterns have different applications and uses. For example, diamond knurling is often used in handles, knobs, tools, and machine components to improve grip and prevent slippage, while other patterns have their own uses and advantages. Here’s a complete breakdown of each type of knurling.

Diamond Knurling

The diamond pattern features diagonal knurls sloped toward both the left and right. This type of knurl is used to prevent slipping, which makes it ideal for use in handles, knobs, and machine parts. It’s characterized by its durability and longevity, making it a perfect choice for applications where the grip needs to withstand frequent and prolonged use.

Besides providing a better grip and durability, the diamond pattern is often suited for high-stress applications, which is why you’ll often find it on tool handles. However, certain drawbacks are associated with this pattern; most notably, it can be quite abrasive and can cause damage to softer materials due to the small size and pointy geometry of the knurls.

Straight Knurling Pattern

Straight knurling produces a straight pattern across the surface, which is why it’s suitable for improving the grip or increasing the surface area of the component for bonding or soldering purposes.

Compared to diamond knurling, straight knurling is a better choice when it comes to more delicate materials, as it doesn’t put as much stress on the workpiece. That’s why this pattern is a good choice for handles and knobs, but it’s also used for decorative purposes.

The drawbacks associated with this type of knurling are that it doesn’t provide as much grip as other patterns, and there is potentially some inconsistency in achieving a pattern.

Right-Handed Knurling

Next to diamond knurling, right-handed knurling is the most commonly used pattern. It produces diagonal knurls sloped to the right, and it’s widely used across various industries as it provides a comfortable grip.

Due to its versatility, a right-handed knurling pattern can be used in various applications, such as handles, knobs, tools, machine parts, barbell bars, jewelry, consumer electronics, and even optical instruments. The reason why it’s one of the most widespread patterns is to accommodate the right-hand grip, as more than 90% of humans are right-handed.

Left-Handed Knurling

Compared to right-handed knurling, left-handed knurling is significantly less common, and it’s often used purely for aesthetic purposes. However, some manufacturers used this pattern in certain applications, such as left-handed tools.

Knurling Grades

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There are three major grades of knurling: fine, medium, and coarse—and the depths of ridges determine the grade. Here’s a breakdown of each grade:

• Fine knurling — Characterized by a precise pattern, it’s usually applied in jewelry, electronics, and optical instruments, as it provides a delicate grip without damaging the surface. The potential drawback is that it doesn’t provide enough grip for some applications.
• Medium knurling — This isn’t a commonly recognized grade; instead, it often refers to a grade that’s between fine and coarse knurl grade.
• Coarse knurling — Coarse knurling is characterized by a pattern that provides a strong grip, even with gloves or in contact with lubricated devices or hands. Its aggressive pattern is often found in tool handles and machinery; nearly all applications that require a strong grip. The aggressiveness of this grade is one of its drawbacks, as it may cause discomfort or even injury to the user.

Knurling Methods and Techniques

When it comes to methods, there are two knurling methods used to produce a knurl pattern:

• Cut knurling — This method implies removing the material from the circumference of the workpiece, leaving the diameter unchanged. The process is best used on harder materials and more complex shapes.
• Form knurling — With this process, the surface material is displaced instead of removed from the workpiece. This means that the resulting knurled surface is of a slightly larger diameter than the stock workpiece. This method is best used on softer materials and smaller parts.

There are several different ways in which knurling is applied to a component; it’s usually done on a lathe or a CNC machine, but it can also be done manually using different knurling tools. Each approach has its advantages and drawbacks.

Manual Knurling

Manual knurling involves using manual knurling tools or simple hand tools (such as needle files) to achieve a certain pattern. This knurling operation is best suited for low-volume production or fabrication of custom parts and can be applied to various products, including pistons, screw heads, footpegs, turntable control knobs, pens, and irregular shapes.

Automatic Knurling

Automatic knurling is achieved by using a specialized knurling machine, and it’s best suited for medium-volume production in which consistency is key. It’s typically used on simple components that can be easily fed into the knurling machine and cut using a knurling wheel.

CNC Knurling

CNC knurling relies on CNC machines or CNC lathe machines to perform the knurling process. Due to its repetition and a high degree of precision, CNC cut knurling is best suited for high-volume production or knurling applications on complexly shaped components.

Knurling Tools

Besides different methods and techniques, it’s also important to mention the knurling tools used to produce a knurling pattern:

• Knurling wheels — These are small, circulative tools that feature a number of teeth or ridges on their circumference. They’re most typically employed in form knurling.
• Knurling inserts — Knurling inserts are small, replaceable tool components that fit into a knurling tool holder. These are great for making a different variety of knurling patterns.

Find Industrial Knurled Parts

Knurling is a metalworking process that involves producing patterned grooves in a material surface, either by cutting the excess material or by material displacement. If you want to learn more about knurling, tool holding, and workholding, check out our extensive library of engineering resources for knurled parts from knobs to screw heads.