What is Knurling: Definition, Process, Pattern and Tips
Machined components may require some post-operations to achieve certain properties. Knurling is one of the finishing processes that can allow having textured finishing on the components.
If you are looking forward to learning about what is knurling, its different types, pros and cons, you can go through this guide below.
What is Knurling?
Knurling is a technique that allows the creation of ridges on the components that have already been machined.
The addition of a knurled finish makes the components have more friction and also prevents it from slippage. It also enhances the visual appeal of the component.
There are different types of patterns that can be achieved through this process in the form of straight lines and diagonals, the knurling tools are used to achieve these patterns.
How Knurling Works?
The component to be knurled is clamped on the lathe, where a knurling wheel or a cutter is pressed with pressure on the surface of that component.
The machine feed is then adjusted in terms of RPMs, and patterns of different types can be created. This tool can help remove the material while the component rotates and creates a rough pattern.
Types of the Knurling Process
There are two main types of knurling processes, which are discussed below:
Machine Knurling
The process of machine knurling uses a lathe or a milling machine to perform the process of knurling. Cylindrical components are knurled through the lathe, and flat components are knurled through the milling machine.
The knurling tool can also pass through the surface so that a complex knurl is formed. Machine knurling is mostly performed using machined metal components to enhance the decorative look and grip or for the purpose of branding.
Hand Knurling
Hand knurling is a process in which a rolling hand tool is used for knurling. The tool is clamped in the cylindrical axis of the component and is rotated by applying pressure so that the knurling can be created on the component.
It also manufactures custom and craftsman-made components. It was widely used before the precise machining tools were evolved.
Types of Knurling Patterns
The process of knurling can generate different types of patterns on the machined components, and these are as follows:
Straight Knurling
Straight knurling is a process that allows the creation of a liner grooved through the axis of the component in a cylindrical shape.
It adds grip to the component and also enhances its looks. It is mostly opted for fitting components. It offers a very precise concentricity and facilitates a tight fit with a low cost of operation.
Annular Rings
Annular rings are created with the knurling process for a decorative purpose or to add grip on the thumbwheels. The process creates thread-like knurls on the component, which is usually observed in screws.
Diamond Knurl
The diamond knurls are created with the help of two straight-cut pattern wheels, which roll at the angle which is on the axis of the cylindrical components. It overlaps the angle grooves and creates a diamond pattern. The angle between the grooves is usually 30 degrees, but it can vary.
Types of Knurl Tools
There are different types of knurling tools, and these are given below:
Knurling Wheels
Knurling wheels are the tools which are used for knurling metals and they have hard steel wheels which help create patterns. They are attached to the knurling tool, and they press themselves against the workpiece to create the knurl pattern.
Knurling Inserts
Knurling inserts are special tools that can easily be fixed on the lathe, and they have a knurl pattern that is programmed and allows creation of the required knurled finish. These inserts are made of carbide steel and offer a wide range of patterns and sizes.
Knurling Dies
Knurling dies are tools that are used in turret lathes, and they help achieve the knurled patterns on the components in cylindrical shapes.
These are made using high-speed steel, and the knurling pattern they create helps cut the inner surface of the component. The component has to be mounted on a tool holder and it creates the pattern by rotating against the workpiece.
Push-Type Knurling Tools
Push-type knurling tools are types of tools that use manual force and are handheld tools for creating knurled patterns. These tools have a knurling wheel with a handle which helps with the movement through the surface of the component to achieve the required knurling pattern.
Floating Knurling Tools
The floating knurling tool is suitable for creating patterns on surfaces that are irregular or have contours.
These tools have the ability to adapt the shape of the workpiece and ensure an accurate pattern. They use spring loaded technique, which helps to align the wheel with the contours of the component.
Pros of Knurling
Some of the advantages of knurling are as follows:
- It enhances the grip and reduces the visibility of wear and tear on the components.
- It allows precision at low cost for the parts that are push-fitted.
- It enhances the visual appeal of the components.
- Knurling adds adhesion to the surface and also improves friction.
Cons of Knurling
The cons of knurling are as follows:
- The process of knurling tends to add deformity to the surface of the component which can impact the strength of the component.
- It may not be suitable for materials that are brittle and hard, like hard plastic or ceramics.
- The process requires skills when it comes to achieving the depth and ridge width.
- Knurling tools may wear out over a period of time, and it has an impact on the results.
- The process is only suitable for components that are small-medium sized.
Applications of Knurling
Some of the applications of knurling are given below:
- It is used for machine handles as it gives a good grip and also protects these handles from wear and tear in the long run.
- A knurled pattern adds adhesion when the metal parts are encapsulated by a composite of polymer.
- In order to offer a malleable and ductile zone to the shaft, knurling can be opted for, and it offers support for a strong coupling.
- Knurling offers surface abrasion tolerance and even offers a decorative look.
Practical Tips for Successful Knurling
In order to attain the best knurling patterns, some of the tips are given below:
- Before knurling, try to make the surface of the component clean from all types of misalignments and contaminants to ensure that appropriate knurling is achieved.
- The knurling tools should be selected keeping in mind the material and required patterns as every tool has different patterns and configurations which should be assessed to attain the desired surface finish.
- The component and the knurling tool both must be lubricated appropriately so that a smooth finish is achieved and heat generation and tool wear are reduced.
- It is important to select the right speed while knurling to get the right pattern.
- Manage the pressure adequately; too much of the pressure may end up damaging the component, and too less may not allow achieving the desired pattern.
Conclusion
The knurling process is one of the crucial processes right after the component is manufactured. Hence, it requires a lot of care and consideration.
If you are looking for an experienced manufacturer offering knurling services, consider DEK. We offer expertise in knurling with a skillful team and the right equipment.
FAQs
How do we measure the size of knurls?
A micrometer can be used to measure over the knurls.
What materials are commonly used for knurling?
Steel and brass are the two materials most preferred when it comes to knurling.
Which machine is suitable for making a knurled finish?
A lathe is used to make the knurled finished components.
What cutting speed is the right choice for knurling operation?
The recommended cutting speed suitable for knurling operation is a maximum of 150 SFPM for 50 meters per minute.
What is the difference between knurling and engraving?
Knurling helps achieve the required pattern by rolling the tools over the surface. Engraving is to cut the material to achieve the desired pattern with the help of a single-point tool.
