Enhancing Surface Grip with a Knurling Tool for CNC Turning

Precision and surface finishes are extremely important quality determinants of parts when advanced machining processes are employed. Use of a knurling tool in CNC turning is an example of a best practice for enhancing grip and texture on round workpieces. Tools are unique in shape and geometry and have been designed to generate a uniform pattern on the workpiece surface for functional and aesthetic appeal. Knurling is still a viable final finishing operation in many industries, including automotive, aerospace, and general manufacturing.

What is a Knurling Tool?

A knurling tool is a cutting/forming tool that embosses a pattern on the surface of a workpiece rotating in a lathe. Unlike other cutting tools, knurling doesn't cut away material. Instead, tools push or displace the material to form straight or diagonal knurl patterns. The result is an aesthetic texture that also gives a good grip for handles, shafts, fasteners, and more.

A knurling for CNC turning is mounted in the tool post of a CNC machine. It exerts a controlled amount of pressure against the surface of the workpiece as it is rotating to create the knurled effect. It must be done with just the right amount of pressure to avoid slipping or distortion, which results in a clean, even finish.

Why Knurling Is Important in CNC Turning

The essential purpose of CNC knurling is to produce a textured surface that adds grip or friction. This is especially beneficial in applications where smooth surfaces might allow slipping or poor handling. Knurled finishes also improve the assembly of press-fit components and give any product a professional, higher-quality appearance.

In addition, knurling can occasionally be used to marginally increase the diameter of a part to fit tightly into another component. The tool for CNC turning becomes an even more crucial accessory in precision manufacturing.

Types of Knurling Tools

There are several different types of knurling that are suitable to produce the desired pattern and quality. The three most common types of tools that you may encounter during CNC turning operations are:

1. Cut Knurling Tool

A cut knurling utilizes sharp-edged wheels that cut into the material to create the pattern. This type is aggressive, which makes it suitable for harder workpieces or when a very clean and precise pattern is required, considering that this knurling technique utilizes smaller forces than other techniques and produces less stress to both the workpiece and machine in general.

2. Form Knurling Tool

A form of knurling uses wheels that displace material rather than actually cutting into the material. Due to being pressed into the surface, this method is often faster than the cutting method and is often used on softer materials such as aluminum or brass. The rollers on the tool press into the surface of the part that is rotating to create the pattern, and this is the most common tool for decorative finishes and adding grip to a surface.

3. The Knurling 

Knurling can incorporate both cutting and forming methods to create a durable and precise pattern. Being able to incorporate both methods allows machinists to push the tool into harder materials while maintaining a reasonable surface finish. This type of tool is used in some applications that balance functionality and aesthetics.

Typical Knurling Patterns

Different patterns may be more or less appropriate depending on the application. When using a knurl tool for CNC turning, the pattern selected is almost as important as the tool used. 

• Straight Knurl—Creates parallel lines along the length of the workpiece. This is most commonly used when a simple, linear grip is required.

• Diamond Knurl—Produces crossed lines to form an interlocking pattern. This is typically the most common knurling pattern and provides good grip and a clean appearance.

• Diagonal Knurl—Creates angled lines and can be used for decorative purposes or to provide a different grip profile.

The patterns are established by the shape of the wheels and the angle at which they were mounted on the CNC tool. When the wheels are properly set up, it is easy to create the proper depth of pattern and consistency.

Advantages of Using a Knurling Tool in CNC Turning

There are several advantages for manufacturers to utilize a tool when conducting CNC turning:

• Improved Grip: The textured surface can make components much easier to handle, especially when slippage may happen.

• Professional Look: Knurled surfaces lend a more finished, high-quality look to parts.

• Fit Tolerance: Knurling will sometimes add a small amount of diameter, which can help when dealing with press fits.

• Lower Cost: Once you have set up, the overall process is quick and consistent, which will provide cost savings at various production rates.

• Material Compatibility: tooling can be used with a variety of materials, such as aluminum, steel, etc.

How to Set Up a Knurling Tool in CNC Turning 

Setting the tool properly is necessary for achieving accuracy during CNC turning. Here are some considerations: 

• Tool Alignment: The tool needs to be aligned squarely in relation to the workpiece; otherwise, the knurling pattern can get distorted, or you may get premature wear to the tool. 

• Applied Pressure: Take appropriate and consistent pressure in order to let the wheels effectively form or cut the patterns. 

• Feed Rate and Speeds: Time to set spindle speed and feed down per material and tool. For forming applications, slower speeds are often a better choice. Cutting tools may run at faster speeds. 

• Coolant: Using some sort of coolant reduces friction and heat, leading to better tool life and finish. 

• Pattern Check: Always run a trial pattern check before beginning production. 

Care and Maintenance of Knurling Tools

If a CNC knurling tool has been used and maintained properly, it should give dependable performance and consistent results for years of service. After using the tool, it is useful to perform cleaning to remove excessive shavings and debris from the metal matrix. Regularly check the wheels for wear and chipping. Always replace damaged wheels, as they may significantly affect the quality of the pattern. Lubricating the tool itself prior to use is another preventative measure. Lubrication will reduce friction and wear and will help to improve the longevity of the tool. 

Uses for Tools

Knurling is typically used on the metal surface in many industries that require grip strength as well as an attractive appearance. In CNC turning processes using knurling, we can make handles and knobs, bolts, and fasteners. The knurl finish not only provides a positive grip but also promotes functionality, comfort, and safety. 

Frequently Asked Questions

Q1. What is a knurling tool for CNC turning used for?
A. It’s used to create textured patterns on cylindrical parts to improve grip and appearance.

Q2. Which materials can be knurled?
A. Common materials include steel, aluminum, brass, and some plastics.

Q3. What’s the difference between cut and form knurling?
A. Cut knurling removes material for a clean finish; form knurling displaces it, ideal for softer metals.

Q4. How can I avoid tool slippage?
A. Ensure proper alignment, steady pressure, correct feed rate, and use coolant.

Q5. How long does a knurling tool last?
A. With proper care and cleaning, it can last thousands of cycles.

Conclusion

A knurling tool is an important finishing process in machining to enhance the aesthetic and performance of the machined parts. Selecting the appropriate tool and setup will allow the manufacturer to achieve a quality, accurate, durable, and visually pleasing finish. Apply proper technique to ensure that you achieve effective results from either cut, form, or die knurling types to ensure maximum longevity of the tooling while achieving repeatable quality results. 

If you are seeking reliable and quality machine products, check out Jaibros. The reputable name is probably not unknown to workshop and professional end users and provides all types of durable and accurate tool types for a CNC turning application.