New Guide Unveiled for Knurling Process

What is Knurling in Lathe Machine?

Knurling is a manufacturing process to create a textured surface on a workpiece in lathe machining. It involves creating a series of small raised and indented patterns on the surface of the component, which increases the surface roughness and friction between the workpiece and other machined parts. In other words, this process improves the grip and anti-slip properties of the workpiece. Commonly, knurling is employed to manufacture parts that require good gripping, including handles, nuts, and bearings.

How does Knurling Work? 

Knurling is a process that uses rollers to apply pressure to the workpiece surface, causing localized plastic deformation to form the required knurl pattern. Here are two ways of the knurled process, hand and machine knurling.

Hand knurling

It involves using hand-knurled tools, such as knurling hammers and knurling wheels, to manually create a regular textured pattern on the metal surface. This method offers high flexibility to customize the pattern, but it is less efficient and requires significant manual operation.

Machine Knurling

The main steps of it are as follows:

1. Securely hold the object in a lathe machine.
2. Mount the knurling tool, consisting of a pair of serrated wheels, in the lathe’s tool holder.
3. Press the knurled wheel against the surface as the lathe spindle rotates the part.
4. The rotating motion of the part, combined with the pressure applied by the knurling wheels, creates a serrated pattern on the material surface.
5. Adjust the depth and pattern by controlling the pressure and speed of the wheels.
6. At last, the resulting knurled surface provides increased friction and grip, making the machined parts easier to handle and turn.

This method is highly efficient and well-suited for mass production, but it affords a more limited range of pattern options and requires dedicated equipment and processes.

Patterns of Knurling

Different knurling patterns are matched to their respective applications, providing varying degrees of grip strength. This section will introduce various knurled patterns in detail.

Straight Knurling

Straight knurling creates a series of parallel raised and recessed patterns. This simple yet effective treatment provides excellent grip and anti-slip properties. The uniform linear pattern not only enhances the functional performance of components like machine tool handles and fasteners but also adds an attractive visual element to the design. Also, it is an economical surface finishing method that is widely utilized across many industries to improve the tactile and aesthetic qualities of products.

Diamond Knurling

Diamond knurling produces a criss-crossing diagonal knurl, forming a visually appealing diamond-shaped appearance. Compared to straight knurling, this intricate pattern provides an exceptionally high level of grip and anti-slip properties, making it an ideal choice for components and tools that require maximum frictional traction. Diamond-knurled surfaces are commonly found on machine tool handles, wrenches, and various metal hardware items from nuts to bolts. Beyond its functional benefits, the decorative diamond pattern also enhances the aesthetic appeal of products.

Right-Handed/ Left-Handed Knurling

The right-handed knurling pattern consists of a clockwise spiral arrangement of protruding or recessed elements. Conversely, the left-handed knurling pattern exhibits a counterclockwise spiral. The primary difference between the two lies in their intended applications. Right-handed knurling is typically employed for components that rotate clockwise, while left-handed knurling is more suitable for parts that turn counterclockwise.

Tools Used for Knurled

1. Knurling Wheels

They are the most common knurling tool, consisting of a pair of rollers with special textures. Knurled wheels come in different materials and sizes to suit different materials and processing requirements.

2. Knurling Inserts

They are typically made of hard alloy and can be mounted on various machine tools, such as lathes or milling machines to impress various knurled patterns onto the component surface.

3. Knurling Dies

Unlike knurling wheels, knurling dies are fixed on the machine tool, and the part rolls on the die to create the knurling pattern. The main types of knurling dies include dual knurling dies, multi-knurling dies and adjustable knurling dies.

4. Push-Type Knurling Tools

These tools are designed to be pushed or fed into the materials to create the knurling pattern. The knurling wheels or dies are mounted on a tool holder that is pushed against the rotating part. This type of tool commonly acts on internal and external knurling applications.

5. Floating Knurling Tools

They have knurling wheels or dies mounted on a floating mechanism which allow them to self-align to the item surface. This helps ensure even pressure distribution and consistent knurling results. Additionally, the floating mechanism allows the tool to compensate for any item irregularities.

Grades for Knurled

Knurling processes typically utilize different grades to meet various application requirements and manufacturing needs. The common grades of knurled surfaces include:

Pros and Cons of Knurled Operations

Benefits:

• Increases surface roughness, enhancing friction and grip, which is beneficial for handling and operation.
• Improve the aesthetic and visual appeal of the component.
• Increase the durability and anti-slip properties of the component.
• Enhance the assembly properties, facilitating connection with other parts.

Limitations:

• Increase manufacturing costs and processing time.
• May affect the strength and structural integrity of the component.
• Prone to accumulating dirt and bacteria, making cleaning and maintenance more difficult.
• Generate certain noise and vibrations, which can be inconvenient for the operator.

Overall, knurled operations require weighing the pros and cons, and deciding whether to adopt them based on the specific application scenarios and requirements.

Tips for the Best Knurled Parts

1. Select appropriate knurling patterns and dimensions
2. Adjust the knurling depth and width appropriately to achieve the ideal surface roughness.
3. Ensure the machine tools are in good condition to minimize vibration and deviations.
4. Adapt the tool material and geometry according to the material characteristics.
5. Implement strict quality control and inspection

Conclusion

Huayi International Industry Group Limited has released a comprehensive article on the significance of knurling as a crucial surface treatment technique in mechanical processing. The article offers an in-depth overview of knurling, including its working principles, common patterns, tools used, and practical operation techniques. The goal is to provide readers with a thorough understanding of this important manufacturing process. With its commitment to providing valuable insights into mechanical processing, Huayi International Industry Group Limited continues to demonstrate its expertise and leadership in the industry.