If your machining tools have a weak grip or they often slip, knurling can prove very useful. Knurling offers a reliable way to improve both appearance and tool grip. In this post we will cover what knurling is, how the process works. We will also see different tools, patterns, advantages and applications of knurling.
What is Knurling?
Knurling adds a textured pattern such as angled, straight or diamond lines to a metal surface. This texture increases grip and improves the look of parts such as fasteners and tool handles. In this process a hardened knurling wheel is typically used which is mounted on a lathe. Raised patterns are created on the surface but the structure of part is mostly unchanged.
Knurling Processes
Manufacturers can choose from two main methods to create knurled surfaces. Each method is suitable for different materials and uses. By knowing how these methods work you can choose the best options for your needs.
Cutting Knurling
In cutting knurling, a tool with sharp teeth is used to cut the pattern right into the material. This method removes metal which makes it suitable for harder materials or when you want a very sharp pattern.
Cutting knurling operates with minimal dependence on blank diameter and gives you more control over pattern spacing. Mostly it is used for fine or detailed knurling on tough metals.
Rolling (Forming) Knurling
Rolling knurling presses a pattern onto a spinning workpiece using hardened wheels. The wheels push the metal aside to create a ridge, so no material is removed. This method works quickly and produces very little waste. It is generally used for cylindrical parts such as handles or knobs. Using the correct blank diameter is important as it prevents pattern errors or double tracking.
Types of Knurling Patterns
Straight Knurling
In straight knurling parallel grooves are produced that run along the length or around the circumference of a part. This method applies less stress than other patterns, that’s why it works well with delicate materials. Mostly straight knurling is used for decorative purposes or to add a moderate grip to handles and knobs.
Also See: What is CNC Grooving
Diamond Knurling
Diamond knurling creates a pattern of intersecting diagonal lines, thus forming diamond shaped textures. In this method two angled wheels are used which rotate against the workpiece at the same time. Compared to straight knurling, this crisscross design provides a better grip. Grooves usually meet at an angle of about 30° which improves both durability and grip.
Helical Knurling
In helical knurling diagonal, spiral grooves are formed that wrap around the part like a screw thread. This pattern not only increases grip on handles & rotating shafts but adds a decorative touch as well. For certain cylindrical components, helical knurling is also used as a cost effective alternative to thread cutting.
Annular Rings
Annular rings create a series of concentric, parallel ridges around the circumference of a workpiece. Mostly you see this pattern on thumbwheels and knobs to improve grip and tactile feedback. For parts that need quick adjustments or frequent handling, annular rings work very well.
Knurling Equipment and Tools
Knurling Wheels
Basically a knurling wheel is a hardened roller with teeth which is used to press patterns onto the workpiece’s surface. You can choose from diamond, straight or diagonal profiles with pitch options between 0.3 mm and 1.5 mm. Manufacturers generally make these wheels from HSS, powder metal or carbide.
Knurling Dies
Knurling dies serve as special tools in thread rolling machines to create threaded or knurled patterns. Usually they are made from Hardened tool steels like DC53 or D2. They can handle workpieces up to 35 HRC in hardness. You can customize dies for different profiles, pitches and materials.
If you work with a manufacturer with strong tooling capabilities such as RICHCONN, you can gain access to custom dies. This guarantees your project gets the best knurling outcomes.
Knurling Inserts
Knurling inserts are mounted on tool holders to create precise patterns on parts. There are two main types of inserts. Cutting inserts which cut the material and forming inserts which press the material. Material choices for these inserts are high speed steel and carbide. Their coated versions last longer because they resist wear.
PushType Knurling Tools
Push type knurling tools press the knurling wheel directly onto the workpiece using force. For short production runs or soft materials, these tools work best. Moreover these are perfect for manual operations and low volume jobs while allowing you to change patterns easily and quickly.
Floating Knurling Tools
Floating knurling tools use a spring loaded mechanism that adjusts automatically to uneven workpiece surfaces. The knurling head can rotate within a 40 degree arc which keeps pressure even. These tools help correct misalignment during use. For contoured surfaces where you need a uniform pattern, they work particularly well.
Benefits of Knurling
Aesthetic Appeal
Knurled patterns give products a professional and unique appearance. You can choose from helical, diamond and straight designs. Due to these patterns, items like jewelry, pens and machine handles look more attractive.
Better Grip
Knurling adds a textured surface which greatly improves grip. This allows you to hold tools and parts more securely, even when they are oily or wet. For handles, knobs and fasteners where control and safety are important, this extra friction is very important.
Assembly Aid
In the knurling process the diameter of parts slightly increases. Due to this change stronger fits can be achieved without extra machining. Moreover this textured surface helps lock mating components together such as gears, bearings and shafts.
Repair Utility
Worn shafts or parts can be restored by knurling. The raised pattern expands the diameter and helps regain a proper fit. For the replacement of parts which are expensive or hard to find, this method works well.
Applications of Knurling
Consumer Products
In many consumer items such as dials, knobs and pens knurling proves very effective. The texture pattern provides users a firm, non-slip grip and adds visual appeal as well. You will often find knurling on writing tools, home electronics and small gadgets which need frequent manual adjustments.
Manufacturing
Manufacturers mostly use knurling on pistons, tool handles and fasteners. This process improves grip and increases torque resistance for items like pliers, wrenches and calipers. In high volume production knurled surfaces help press fit assemblies remain reliable and secure.
Automotive Industry
Knurling performs an important part in the automotive industry for axles, wheel hub bolts and fasteners. The knurled surface increases friction which prevents parts from loosening under heavy loads Moreover knurling helps create strong connections between rotating shafts, gears and bearings which boosts performance and safety.
Sports Items
To give athletes a secure grip during tough workouts, knurling is often used on gym equipment and barbell bars. Moreover BMX pedals, dart grips and motorcycle handlebars feature it for better control and safety. These knurled patterns stop slippage and make athletic gear safer and easier to use.
Medical
In the medical field knurling is often used on walker handles, IV poles and orthopedic tools to improve safety. Surgical instruments also use knurling for easy identification and cleaning in sterile settings. This design choice helps prevent slipping in fluid exposed environments.
Tips for Optimal Knurling
Material Selection
When choosing a material, always consider its hardness and flexibility. Soft metals like brass and aluminum work best with form knurling tools. If you are working with hard materials like stainless steel use cut knurling tools to prevent the surface from cracking. For plastic or wood, choose low profile patterns so that the material does not deform.
Our material engineers at Richconn guide clients in selecting the right metals and plastics for knurling. Due to this support you can be protected against problems like cracking or poor pattern quality.
Proper Setup
Make sure to align the tool exactly perpendicular to the workpiece. To prevent pattern errors or double tracking, clamp the workpiece tightly and line up the tool. Depending on the hardness of material, adjust feed rates to 0.1-0.4mm per revolution and set speeds from 90 to 600 RPM.
If you need to knurl tough materials like titanium, it’s better to work with specialists like Richconn. We use 18 axis CNC lathes which can automatically set the best feeds and speeds to stop chatter.
Lubrication
During knurling, use a lubricant or cutting fluid on both workpiece and tool. Lubrication helps in preventing tool wear, reduces friction and produces a smoother finish. Choose cutting oil for steel. Whereas for aluminum or brass, a cooling emulsion works better.
Tool Maintenance
After every use, clean your knurling tools to clear away debris and reduce wear. Make sure that no teeth are missing and also check for rust or any damaged parts. To minimize friction and extend tool life, apply lubricant to moving components. Always store your tools in a dry area to keep corrosion away.
To Sum Up
In short, knurling changes plain surfaces into components that are easier to grip, more attractive and highly functional in many industries. You can get dependable results for any project by understanding the right knurling methods, tips and patterns.
If you want precise knurling and expert surface finishes then Richconn is the best option. You can contact us anytime.
Related Questions
What is the ideal surface speed for effective knurling?
Harder materials like stainless steel work well at speeds of 90 to 130 SFPM. For softer materials such as aluminum or brass use surface speeds between 35 and 50 SFPM.
How does material hardness affect the knurling process?
Knurling on hard materials can quickly wear out the tools and due to this patterns become shallow or uneven. Softer materials, on the other hand, are simpler to knurl but too much pressure might deform them.
Can knurling be performed on plastic or non metallic materials?
Yes plastics, leather, wood and glass can be knurled. Use lower speeds and less pressure because these materials are less heat resistant and more brittle.
What are the standard pitch sizes used in knurling patterns?
Typical knurling pitches are 64, 96, 128 and 160 DP. For diagonal and diamond knurls, 14, 21 and 33 TPI are also standard.
Are there CNC specific knurling techniques?
For CNC knurling, programmed toolpaths, multi head tools and spindle locks are needed. These features help you in creating automated and precise patterns.
Can knurling be used to restore worn out mechanical shafts?
Yes knurling can be used to restore worn shafts. The knurling process raises the surface, improves fit tolerances and compensates for lost material.
How is knurling different from serration or engraving?
Knurling displaces or cuts material to create a patterned texture for grip. Whereas in serration and engraving, material is removed for making sharp edges or decorative lines not raised patterns.
