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In the field of mechanical engineering, knurling technology is both common and critical. By using specific tools, regular textures or patterns can be created on the surface of a workpiece. Through special treatment of the knurling wheel, different materials can be processed into products of various shapes and patterns, such as gears, bearings, etc. This process not only enhances the aesthetic value of the workpiece, but also significantly enhances its functionality and performance. Knurling is loved by more and more engineers for its unique charm and is applied to various fields. So, what is the ultimate goal of knurling technology? How is it produced and applied in different fields? This article will explore the multiple meanings of knurling in depth and show its wide application in multiple industries.

What is Knurling?

Knurling is actually a precision machining method that creates unique patterns and lines on the surface of mechanical parts by hand or on a lathe. Knurling can make mechanical parts produce concave and convex textures, so as to achieve aesthetic and practical purposes. This knurled texture significantly increases the coefficient of friction on the surface of the component, thus ensuring the stability and anti-slip properties of the product or object. Knurling can give components different appearance and texture characteristics. At the same time, knurling is a unique visual experience that is appealing and often more appealing than a single smooth surface.

In addition, knurling is a classic method of material reduction, which creates a textured effect by applying a certain amount of pressure or scraping off the material on the surface of the workpiece. In this article, we will explain how to use the knurling method to manufacture cylindrical parts with special shape and pattern characteristics. The design of the knurling tool often has a unique pattern, and when it is used on a cylindrical mechanical part, it can present a similar pattern on its surface, such as diagonal or straight stripes. The knurling machine can also be used for the forming of other complex shapes and special structural parts. As a result, we have the ability to create a unique texture on the surface of the product using knurling tools with unique patterns.

What is the purpose of knurling?

In the field of machining and manufacturing, knurling technology plays a significant role, and its key uses are as follows:

• Improved grip: The knurling process creates a surface texture and enhances the coefficient of friction for a more secure grip, such as a screwdriver handle, reducing the risk of slipping.
• Add aesthetics: knurling technology creates a unique visual effect, enhances the appearance and quality of the product, and makes the product stand out.
• Anti-slip safety: In wet or greasy environments, the knurled surface removes moisture and grease, such as wrenches,to reduce the risk of slippage and ensure safe operation.
• Optimized operation: The knurled design makes the tool rotate or hold more smoothly and improves work efficiency, such as knobs and handles in machining.
• Extended life: The knurling process improves the surface wear resistance, resists daily wear and tear, prolongs the service life of the product, and reduces maintenance costs.

What are the different types of knurling patterns?

The knurling pattern varies according to the functional and aesthetic needs of the workpiece, and is made by knurling with special tools and knurling wheels. Choosing the right pattern is critical to the end use of the product, and the common knurling patterns are as follows:

1. Straight knurling: Forming parallel ridges on the surface of the workpiece, mainly used to improve grip and often used when complex textures are not required. The operation is to roll with a knurled tool on the lathe to form a uniform straight ridge, which is suitable for tool handles, knobs, etc., and is easy to hold.
2. Diagonal knurling: The ridge line is inclined on the surface of the workpiece, the pattern is more dynamic, and the visual effect is better. Processed by roller tools, it has both grip and aesthetics, and is commonly found in consumer decoration, such as pens, handles, etc.
3. Right-handed knurling: The surface has a diagonal ridge that slopes upwards from left to right, which is machined by knurling tools on equipment such as lathes. Used to improve grip or appearance, like hand tools, tool handles, etc.
4. Left-handed knurling: In contrast to right-handed, the ridge line slopes downward from left to right, the same principle but mirrored in the direction. It is suitable for parts that require a specific texture orientation, and is used to improve grip as well as right-hand rotation, such as tool handles.
5. Diamond knurling (cross knurling): A diamond-shaped pattern that forms a criss-cross and is made by two sets of reversed inclined knurling wheels pressed into the material. It has strong grip and is used in tool handles, barbell bars and other slippery places, and is commonly used in various industries.
6. Spiral knurling: A spiral pattern is formed along the surface of the workpiece, and the knurling wheel is rolled at an angle to improve the friction of rotating or firmly gripping parts, and can also be used for aesthetics.
7. Annular ring: Formed in the circumference of the workpiece in the shape of concentric parallel ridges, with a lathe or special machine, pressed or rolled by knurling tools. It is easy to process and can enhance the grip of cylindrical objects, commonly found in tool handles and barbell bars.
8. Concave knurling: The pattern is bent inward to form a concave shape and is embossed by a special knurling wheel.It is suitable for tool handles, bicycle handlebars, etc., which need to be held comfortably, and it is not easy to get tired of hands after long-term use.
9. Convex knurling: There is a circular pattern that protrudes outwards and is embossed by a special knurling wheel. It is suitable for tool handles that require a smooth and firm grip, etc., and can reduce hand pressure points.
10. Square knurling: Forming a square grid pattern, which is cut or rolled with a knurling tool with a specific tooth shape. Strong grip, used for screw heads, knobs and other slippery places.
11. Beveled knurling: There is an oblique ridge pattern, made with a knurling tool with oblique teeth. Improves the grip of cylindrical objects, suitable for tool handles, etc., and has a better handling effect when rotating.

How Do Diamond vs. Cross Knurling Differ?

The following is a comparison table of diamond knurling and cross knurling, which provides a detailed analysis of the differences between the two from multiple dimensions:

Compare dimensions	Diamond knurling	Cross knurling
Definition and pattern morphology	A type of reticulated knurling, the surface is crossed diagonally to form a regular diamond-shaped bump or dent, usually at an angle of 45° or 30°, emphasizing symmetry and decoration.	A variant of straight ridge knurling, the grain is a straight line that crosses vertically to form a cross-shaped groove or bulge, with a greater focus on functional grip.
Processing method	Special knurling wheels are required, and hard materials (such as stainless steel) need to use two-wheel cutting tools to achieve clear lines through oblique cutting and multiple rolling.	Using straight-grain knurling wheels, the criss-cross pattern is formed through a single extrusion or cutting, and the tool is more versatile.
Typical application scenarios	High-friction handheld devices (subway handrails, fitness equipment), decorative surfaces, both non-slip and beautiful.	Tool handles, knobs, jewelry, and other scenarios that require basic anti-slip functions have a simple and practical design.
Visuals	The lustrous and regularly arranged diamond shapes enhance the metallic texture, making it suitable for designs that require high recognition.	The straight cross pattern is simple and clear, the grip is visualized but the decoration is weak, and it tends to be utilitarian.
Process challenges	When machining hard materials, the radial pressure is high, which requires special tools and process control, and the cost is high.	The texture is simple and has a wide adaptability to the material, but the complex design may weaken the material structure.
Differences in user perception	When held, the skin is embedded in circular pits to distribute pressure, comfortable and non-slip; Visually more refined and high-end.	Straight-grained bumps provide direct friction, but sharp edges may increase the risk of scratching and are less decorative.

Diamond knurling is better in terms of decoration and comfort, and is suitable for designs that need to balance beauty and functionality; The cross knurling is based on simple and efficient grip, which is more suitable for scenes with high requirements for anti-slip but low decorative requirements.There are significant differences in processing complexity, cost, and end-user experience.

Which Materials Require Special Knurling Parameters?

The following is a summary of the special parameters required for knurling of aluminum alloys (6061-T6), stainless steel (316L) and engineering plastics (POM):

Material	Special knurling parameters
Aluminum Alloy(6061-T6)	1.Pre-cooling: Must be pre-cooled to -10°C to prevent the material from sticking to the knife. 2.Feed rate: The feed rate should be controlled at ≤0.1mm/rev to ensure the processing quality. 3.Roller hardness: The hardness of the rollers needs to reach HRC 62+ to cope with the hardness characteristics of aluminum alloys.
Stainless steel (316L)	1.Cutting oil: Vulcanized cutting oil needs to be applied to reduce the local temperature rise of 800°C during processing. 2.Pressure compensation: The pressure needs to be increased to 1200N/cm² to compensate for the work hardening of stainless steel.
Engineering Plastics (POM)	1.Roller temperature: The temperature of the roller should be kept at 80°C, and the hot rolling process should be adopted. 2.Tattoo depth limit: The grain depth should be limited to 0.2mm to prevent cracking of the material.

Analysis note：

• Aluminum Alloy(6061-T6): Due to the stickiness of aluminum alloys, pre-cooling is necessary. At the same time, controlling the feed rate and roller hardness can ensure stability and surface quality during machining.
• Stainless steel (316L): The work hardening phenomenon of stainless steel is obvious, so it is necessary to increase the machining pressure. The application of vulcanized cutting oil can effectively reduce the machining temperature, reduce tool wear and workpiece deformation.
• Engineering Plastics (POM):POM material is temperature sensitive, and the hot rolling process can improve the processing efficiency and quality. Limiting the grain depth is to prevent cracking of the material due to excessive deformation.

What Are the Hidden Costs of Improper Knurling?

In the knurling process, if not done properly, a series of hidden costs will be incurred, mainly reflected in the following aspects:

Tool loss

When machining steel parts with tungsten carbide rollers, the tool life is very short, and it is generally only 200 to 300 pieces, and the tool has to be changed frequently, which greatly increases the cost. Moreover, every time a tool is replaced, not only does it cost you to buy a new tool, but you also have to stop the production line, which increases the cost of replacing the tool due to tool wear and tear and downtime by 0.15 to 0.35 per workpiece.

The defective rate increases

For workpieces with high precision requirements such as automobile parts, if the knurling pattern is misaligned by more than 0.05mm, it can only be scrapped, and the scrap rate will go up all of a sudden. In addition, material springback often results in insufficient depth of knurling, which can lead to rejects of up to 12%, further driving up costs.

Reduced productivity

Frequent tool changes, constant equipment adjustments,and increasing downtime are slowing down the overall production efficiency. Those defective products have to be reworked or re-produced, which takes up a lot of production resources and makes the production progress slower.

Quality control cost

In order to ensure the accuracy of the knurled pattern, it is necessary to carry out quality inspection more frequently, and the inspection cost will naturally increase. Moreover, more people have to be arranged to adjust equipment and deal with defective products, and labor costs have also gone up.

Material waste

There are more and more defective and scrapped workpieces, materials are wasted, and the cost of raw materials is also rising. With more scrap, inventory management becomes more complex, and inventory costs increase.

Loss of customer trust

With so many problems in production, it is easy to lead to delivery delays, and customer satisfaction will definitely suffer. If the defective rate is high, there will be more customer complaints, and the company's reputation will be damaged.

Equipment maintenance costs

The equipment is constantly adjusted and tools are replaced, and the equipment wears out faster, and the cost of maintenance and repair is higher. In order to be able to replace them in time, more spare parts had to be stocked, and the inventory cost increased by another amount.

What Are the Alternatives When Knurling Fails?

In the event of knurling failure, we can consider the following alternatives:

Microblasting

Microblasting uses 60 - 80 mesh alumina particles to achieve a surface roughness of Ra 2.5 - 4.5μm. From a cost-effectiveness point of view, it is 40% less expensive than knurling, so if you have a limited budget, it is a good choice. However, its abrasion resistance is not ideal, only one-third of knurling, so it is just right to use it in places where the wear resistance is not high.

Laser etching texture

Laser etching with a 20W fiber laser can reach a scanning speed of 3000mm/s. It is very accurate, and can achieve custom logo textures with an accuracy of 0.05mm, which is useful for those applications that require high precision, such as the appearance texture design of high-end electronic products. What's more, it has the flexibility to design a wide variety of complex textures and patterns, which is especially suitable for personalized customization needs, whether it is a unique artistic shape or a niche design style.

Chemical etching

Chemical etching is the use of a chemical solution to etch the surface of the workpiece to form the desired texture. It is suitable for a wide range of materials, such as common stainless steel, aluminum alloy and other metal materials. The cost is relatively low, but it is necessary to pay attention to the treatment of chemical waste liquid, after all,environmental protection problems can not be ignored, and the chemical waste liquid treatment process must be strictly controlled to avoid pollution to the environment.

Electrochemical machining

This type of machining is the formation of a texture on the surface of the workpiece by means of an electrochemical reaction. Its advantage lies in its high precision and the ability to perform fine texturing of complex shapes. From the perspective of environmental protection, it is relatively environmentally friendly and will not produce a large amount of polluting waste. However, the disadvantage is that the equipment investment is relatively high, and it is necessary to invest a large amount of money in the early stage to purchase professional equipment.

Machining texture

With the help of CNC machine tools, milling, engraving and other methods are used for texturing. It can achieve high-precision texturing and is suitable for high-volume production projects. However, there is also the problem of high equipment investment, but if the project requires high precision and is produced in large quantities, in the long run, this method can still ensure product quality and production efficiency.

Surface coating

Surface coating is the spraying or depositing of a textured coating on the surface of the workpiece. A wide range of coating materials can be used, such as ceramics, polymers, etc. Its wear resistance will vary according to the different coating materials,so it is necessary to choose the appropriate coating material according to the specific application scenario, such as ceramic coating can be selected on industrial parts that require high wear resistance; In some applications where aesthetics and corrosion resistance are required, polymer coatings may be more suitable.

Hot imprint

Hot imprinting is the process of creating a texture on the surface of the workpiece by applying heat and pressure. It is mainly suitable for non-metallic materials such as plastics, rubber, etc. The cost is relatively low, and the efficiency is very high in mass production, and the products with the same texture can be quickly copied, so they are widely used in the large-scale production of plastic products and rubber products.

Summary

The purpose of knurling is far more than simple surface decoration. It is a perfect combination of functionality and aesthetic value. By enhancing friction, providing decorative effects, ensuring anti-slip function, optimizing operating experience and improving durability, knurling plays an important role in many fields such as machinery, home decoration, and fitness equipment. With the development of CNC technology, the precision and consistency of knurling technology will be further improved, and its application scenarios will continue to expand,continuously bringing innovation and value to all walks of life.

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FAQs

1.What is Knurling? What is its purpose?

Knurling is a metalworking process that forms regular or irregular uneven textures on the surface of a workpiece through rolling tools, and is commonly found in mechanical parts, tool handles, and other scenarios. The core purpose is to enhance functionality (e.g. anti-slip, anti-rotation, improve grip stability) and aesthetics (to give the product a unique decorative effect through texture design to enhance visual recognition). For example, in wet environments, knurled surfaces significantly reduce the risk of slippage; In precision instruments, knurled textures can improve operational accuracy and user experience.

2.What is the importance of knurling?

The importance of knurling is reflected in the dual dimensions of safety and value enhancement. At the functional level, it ensures the stability of tools and mechanical parts in high-frequency operation by increasing the surface friction coefficient, and avoids operation errors or accidents caused by sliding; At the aesthetic level, knurling can give a product a sense of sophistication and brand recognition, for example, high-end tools often show quality through knurling texture, thereby increasing the market premium ability. In addition,knurling hides processing marks,improves surface finish, and enhances the overall texture.

3.What are the two reasons for knurling?

The two core reasons for knurling are: function-driven (e.g. anti-slip, anti-loosening to ensure operational stability) and design-driven (to increase the added value of the product through textural aesthetics). At the functional level, knurling can optimize the human-computer interaction experience, for example, the knurling design of knobs and handles can significantly reduce operating fatigue; At the design level, customized knurled textures can become brand identity, such as in car interiors or luxury accessories, knurling is often used to convey process details and brand tonality, forming a differentiated competitiveness.

4.What are the advantages of knurling?

The advantages of knurling include: increased friction (anti-slip and anti-off, improve operational safety), wear resistance and durability (texture enhances surface hardness and prolongs service life), and aesthetic and exquisite (through customized texture to enhance product added value and enhance market appeal).

Resource

Knurling