Knurling is one of those manufacturing processes that’s easy to overlook—until you actually need it. Whether it’s the textured grip on a metal tool handle or the patterned finish on a thumb screw, knurling plays a small but important role in how parts are used, assembled, and handled. Despite its simple appearance, knurling involvs specific techniques, tools, and design choices that can significantly affect the functionality and quality of a finished component. This article breaks down what knurling is, why it’s used, and how it’s done.
What is Knurling?
Knurling is a manufacturing process used to create a textured pattern on the surface of a material, typically metal. It’s most commonly applied on cylindrical parts using a lathe, where a patterned tool presses or cuts into the surface to form a series of small, regular ridges. These patterns can vary—some look like straight lines, while others form diamond or angled shapes.
The purpose of knurling is mainly functional. It adds grip to parts like tool handles, knobs, and fasteners, especially where bare metal would otherwise be too smooth to hold comfortably. In some applications, knurling also helps with press-fitting parts together by increasing friction between mating surfaces. Beyond function, it can also be used for aesthetic reasons or as a quick way to differentiate parts.
Types of Knurling
| Type | Pattern | Description | Applications | Advantages | Disadvantages |
|---|---|---|---|---|---|
| Straight Knurling | |||||||||||| | Parallel lines running along the length of the workpiece | Tool handles, adjustment knobs, thumb screws | Easy to machine, good grip, low cost | Limited grip in one direction |
| Diamond Knurling | ◊◊◊◊◊◊◊◊ | Crossed diagonal lines creating diamond-shaped patterns | Hand tools, grips, precision instruments | Excellent grip in all directions, attractive appearance | More complex to machine, higher cost |
| Left-Hand Diagonal | //////// | Diagonal lines slanting to the left | Specialty tools, decorative elements | Good directional grip, moderate cost | Grip varies with direction |
| Right-Hand Diagonal | \\\\\\\\ | Diagonal lines slanting to the right | Specialty tools, decorative elements | Good directional grip, moderate cost | Grip varies with direction |
| Fine Knurling | ▪▪▪▪▪▪▪▪▪▪ | High TPI (threads per inch) creating a fine texture | Precision instruments, medical devices | Smooth feel, precise grip, professional appearance | Less aggressive grip, requires precision tooling |
| Coarse Knurling | ▬▬▬▬▬▬ | Low TPI creating a rough, aggressive texture | Heavy-duty tools, industrial applications | Maximum grip, works with gloves | Rough feel, can be uncomfortable |
| Medium Knurling | ■■■■■■■■ | Medium TPI providing balance between grip and comfort | General purpose tools, handles | Good grip/comfort balance, versatile | May not excel in specific applications |
| Annular Knurling | ○○○○○○○○ | Circular rings around the circumference | Push-fit assemblies, press-fit components | Excellent for retention, uniform stress distribution | Limited grip for rotation, specialized tooling |
General Overview of How Knurling Works
1. Secure the Workpiece
The part to be knurled is mounted in a lathe chuck or collet, ensuring it’s firmly held and centered.
2. Select the Knurling Tool
A knurling tool with the desired pattern (straight, diamond, or helical) is chosen. Tools can either cut into or press against the material depending on the type.
3. Align the Tool
The knurling tool is aligned squarely with the workpiece to prevent uneven or double tracking of the pattern.
4. Set the Lathe Speed
A relatively slow spindle speed is used to reduce vibration and prevent damage to the part or tool.
5. Apply the Tool to the Surface
The knurling wheel is pressed (form knurling) or fed (cut knurling) against the rotating part with consistent pressure.
6. Form the Pattern
As the tool moves along the surface, it creates the knurled pattern by displacing (or in cutting, removing) material.
7. Inspect the Pattern
The finished knurl is checked for depth, consistency, and alignment. Any irregularities like double tracking or chatter are addressed.
8. Optional Cleanup
Depending on the application, a light sanding or polishing may be done to smooth sharp edges or debris.
Tips on Avoiding Common Knurling Issues
One of the most common issues in knurling is double tracking, which happens when the knurling tool doesn’t align properly with the workpiece and creates a mismatched or overlapping pattern. This usually means the pitch of the knurl doesn’t evenly divide into the circumference of the part. To avoid this, it’s important to match the knurl tool pitch with the part diameter as closely as possible, or use a self-centering knurling tool if available.
Other problems include tool chatter or shallow patterns, which can result from using too little pressure or running the lathe at too high a speed. Making sure the workpiece is rigidly mounted, using a steady rest if needed, and keeping lathe speeds low can help produce a clean, consistent knurl.
Parting Thoughts
MISUMI USA offers a wide range of knurled parts and components—both standard and configurable—including knurled knobs, thumb screws, socket head cap screws, and more. If you’re unsure which knurled product best suits your application, our engineering team is here to help. For more technical insights, explore our other manufacturing-focused articles, such as Comparing Stainless Steels: 18/8 vs. 18/10 vs. 18/0.
Browse Knurling ProductsAuthor: Scott Bredemann | Updated: 6/12/2025
Disclaimer:
The content on this webpage is for informational purposes only. MISUMI makes no guarantees, expressed or implied, regarding the accuracy, completeness, or validity of the information. Performance parameters, tolerances, designs, materials, or processes should not be assumed to reflect third-party suppliers’ or manufacturers’ deliverables within MISUMI’s network. Buyers are responsible for specifying their part requirements