Every secure grip starts with a precision texture. But that heart-pounding “sssss” slipping sound may come from a wrong choice.
You hold an expensive flashlight, turn the focus ring on a camera lens, or tighten the knob of a precision instrument. You expect to feel a solid, non-slip, and controlled touch – this is the masterpiece of knurling. However, if the texture under your fingertips is too shallow, the wrong direction, or the material is not matched, the expected secure grip will disappear in an instant. Instead, it is the unsettling slippage of the metal surface and the feeling of loss of control during precision adjustment, which may even cause expensive tools to fall out of your hands, precious parts to be scratched, or critical operations to be unable to be completed.
This frustrating feeling of loss of control is often not an accident, but the result of a fundamental misunderstanding: using the wrong knurling type or method on the wrong workpiece or need.
Knurling is far more than providing a beautiful texture. It is an engineering art of “printing” functionality on the metal surface. It is about safety, precision and reliability. So how is this process of giving metal “grip” achieved on a lathe? And what is the core executor?
The answer lies in the lathe knurling tool. It is the silent but crucial partner next to the rotating workpiece, responsible for “imprinting” the designed texture – whether it is a diamond grid, parallel straight lines or other precise patterns – accurately, consistently and firmly on the metal surface. Understanding it is the first step to unlocking the perfect knurling and avoiding the “slip nightmare”.
Quick reference table of knurling main purpose, description and typical applications
| Knurling Purpose | Description | Typical Applications |
|---|---|---|
| Functional Grip | Creates texture on the surface to significantly increase friction and prevent slipping during operation. | Tool handles, knobs, fasteners |
| Aesthetic appearance | Create unique decorative textures on metal surfaces to enhance visual appeal (often industrial style). | High-end audio knobs, watch crowns, pens |
| Press Fit | By increasing the effective diameter of the shaft surface, the shaft can be pressed more tightly into the hole to form an interference fit. | Fix the bearing and pin in the hole |
This guide will detail how knurling tools for lathes work, show different types of knurling, explain the knurling process step by step, and use a real-life example to demonstrate how a perfect knurling can enhance the value of a product. Finally, we will explain the key differences between knurling and turning.
Here’s What You’ll Learn
- How the three core components of a knurling tool work together: A deep dive into the design and function of the toolholder, the knurling wheel (the soul), and the different knurl types (straight, diamond, twill).
- Five steps to perfect knurling on a lathe: From precise centering to decisive press-in to steady cutting, master the key steps to ensure a clean, flawless texture.
- Case study: How knurling changed the fate of a professional diving flashlight: Reveal how we solved the grip failure problem in extreme environments with deep-groove diamond knurling, improving product reliability and sales.
- The nature and limitations of knurling: A clear explanation of the fundamental difference between knurling and turning, its core uses (gripping/decoration/press-fit), and the range of materials it can be used for.
- Take action now: Learn how to make knurling a functional and aesthetic addition to your product, and get professional advice and processing services.
Now, let’s start to learn more about knurling tools and master this key process that turns smooth metal into a reliable gripping surface.
Why trust this guide? Precision from LS CNC workshop
At LS, we view knurling as a science of precision plastic deformation under high pressure, not just simple cutting. The core lies in the precise coordination of three parameters: spindle speed, feed rate and knurl wheel pressure.
Speed (RPM): Precisely calculated based on the material (such as medical grade alloys, stainless steel) and diameter to ensure ideal plastic flow of the material and avoid accumulation or overheating.
Feed rate: Strictly matched with the speed to ensure continuous and clear texture. Too fast will cause tearing, too slow will cause hardening or deformation. We have accumulated a huge database of material-TPI combinations.
Knurl wheel pressure: The key to success or failure. Insufficient pressure will cause blurred texture and loss of functionality; too much pressure will damage the roundness of the workpiece and produce burrs at the least, or even damage expensive tools and even endanger the accuracy of the lathe spindle. Its precise setting and stable control rely on high-rigidity equipment, precision tooling and strict monitoring.
Functional case: Human-machine interaction optimization of medical knobs
We have solved the problem of surgeons slipping when operating medical knobs with gloves. This is essentially a functional failure of the human-machine interface.
Root cause of the problem: The original TPI (number of teeth/inch) was too high, the contact surface of the tooth top was small; the depth was insufficient and could not penetrate the glove to provide effective friction.
Precision optimization:
Reduce TPI, increase the contact area of a single diamond-shaped protrusion, and provide a better “gripping platform”.
Accurately deepen the embossing depth (to ensure structural strength) so that the texture effectively “bites” the glove material.
Fine-tune the pressure to ensure that the texture is full and sharp under the new TPI and depth without excessive deformation.
Result: The delivered knob has been tested and significantly improved the control force and accuracy of gloved operation. We deliver functional solutions that have been verified by engineering.
This guide embodies LS’s deep understanding of the knurling process: it is the intersection of material science, precision control and functional design. Through countless experiments, measurements and failure analysis, we ensure that knurling is upgraded from decoration to a carrier of reliable function of parts. Trusting LS means believing in the art of precise plastic deformation.
Anatomy of a Knurling Tool: How Does It Go from Smooth to Rough?
“The knurling tool itself is an ingenious mechanical device that works not by ‘cutting’ but by ‘pressing’.” This sentence accurately summarizes the core secret of knurling. Unlike turning or milling, which removes material by a sharp blade to shape the shape, knurling is a cold forming process. It uses strong pressure to cause permanent plastic flow and displacement of the metal on the surface of the workpiece, thereby “carving” the desired texture with almost no chips. This unique deformation method gives the knurling texture excellent wear resistance and strength.
Overview of Knurling Tool Core Components and Functions
| Component | Core Features | Core Function |
|---|---|---|
| Tool Body | Steel handle, lathe clamping | Provides rigid support and pressure transmission basis |
| Knurling wheel | Hardened tool steel wheel, free rotation | Plastic deformation of metal by pressure to generate texture |
| Knurling type | Straight/diamond/twill three mainstreams | Meet different functional and aesthetic needs |
1. Tool body: the cornerstone of strength
The body of the knurling tool is a solid steel shank. It is firmly clamped on the lathe tool holder like a normal turning tool. This seemingly simple structure is crucial:
- Rigid support: The body must be extremely strong to ensure that it will not bend or vibrate when huge radial pressure is applied. Any deformation will cause the pattern to be blurred or uneven.
- Stable platform: It provides a stable mounting reference for the knurling wheel, ensuring that the axis of the knurling wheel and the axis of the workpiece maintain a precise and constant relative position.
- Force transmission: It is the ultimate bearer and transmitter of the strong pressure applied by the lathe to the workpiece.
2. Knurling wheel: the creator of texture
The “soul” of the knurling tool lies in its knurling wheel. They are usually two (or more) small wheels made of hardened tool steel, with the required pattern (straight lines, oblique lines or diamond grids) precisely engraved on the surface. The key feature is that they can rotate freely around their own axis.
- Working principle: When the tool is pushed against a high-speed rotating workpiece, the knurling wheel is driven to rotate under pressure by the friction of the rotating workpiece instead of sliding friction. The raised pattern tips on the wheel surface are pressed into the surface metal of the workpiece with extremely high local pressure (up to several tons).
- Plastic deformation: The metal in the pressed area undergoes plastic flow and is “squeezed” to the sides and front of the pattern depression, forming precise grooves that are opposite to the convex and concave of the knurling wheel.
- Classic combination – diamond knurling: The most common “diamond knurling” (diamond mesh) tool is equipped with a left-handed spiral tooth knurling wheel and a right-handed spiral tooth knurling wheel. When they are pressed on the workpiece and rotated at the same time, the left-hand wheel presses out the right-handed oblique grooves and the right-hand wheel presses out the left-handed oblique grooves, and the cross-overlapping forms a clear and uniform diamond-shaped raised grid pattern. The hardness and precise geometry of the knurling wheel directly determine the quality and durability of the final texture.
3. Different knurling types: patterns with different functions
The choice of knurling texture depends on the application requirements:
- Straight type: Two knurling wheels with parallel straight teeth are used. They press parallel straight grooves on the surface of the workpiece. This texture mainly provides unidirectional grip and is often used for tool handles, knobs or shaft parts that require press fit (using the interference of the teeth to achieve a tight fit). The structure is simple and practical.
- Diamond: As mentioned above, it is formed by the combination of a left-handed and a right-handed knurling wheel. Its iconic cross-diamond raised grid provides excellent grip in all directions, while having a classic and beautiful appearance. This is the most widely used knurling type, taking into account both functionality and decorativeness.
- Twill type: Usually only one knurling wheel (left-handed or right-handed) is used. It presses inclined parallel grooves in a single direction on the surface of the workpiece. This texture provides grip in a specific direction and is sometimes used for decorative purposes or as a simplified alternative to diamond knurling.
The knurling tool is supported by its solid body, relying on the free-rotating, hardened knurling wheel with precise patterns to make “cold welding”-like plastic contact with the rotating workpiece surface under great pressure. The metal is not cut off, but precisely “extruded” and “flowed” into designed grooves and protrusions – whether parallel straight lines, unidirectional diagonal lines, or classic diamond grids – thus magically transforming the smooth metal surface into a rough texture with specific functions and beauty. This reflects the wisdom of the ingenious combination of “force” and “shape” in machining.
Knurling operation on a lathe: see step by step
“Knurling requires patience and precision, not brute force. It’s a process that has to be done right the first time.”
Knurling operation quick reference table
| Steps | Core objectives | Key parameters | Common errors | Safety warnings |
|---|---|---|---|---|
| 1. Preparation | Stable clamping and precise diameter | Diameter tolerance ±0.05mm | Loose clamping/wrong diameter | Wear protective glasses |
| 2. Tool centering | The roller is strictly aligned with the spindle center | Use the tailstock center to assist | Height deviation>0.2mm | Turn off the power to adjust |
| 3. Initial press-in | Press-in decisively at one time | Press-in depth = tooth height 30-50% | Hesitation causes slippage | Stay away from the rotating body |
| 4. Execute knurling | Low speed + sufficient cooling | Speed 50-150rpm | Insufficient cooling/excessive speed | Prevent iron chips from splashing |
| 5. Exit inspection | Clear texture without defects | Completely cover the surface | Failure to withdraw the tool in time | Touch after stopping |
Step 1 – Preparation
Core Task: Lay the foundation for operation
- Workpiece clamping: When using a three-jaw chuck to clamp, ensure that the clamping length is ≥ 1.5 times the workpiece diameter (for example, a φ30mm workpiece must be clamped at least 45mm). Tighten the tail end with a movable center to eliminate radial runout (controlled within 0.05mm).
- Diameter finishing: Knurling will increase the diameter by about 0.1-0.3mm (depending on the pattern density), so the final turning diameter needs to be calculated according to the formula:
Finished product diameter = target diameter – knurling expansion
For example, if the target is φ20mm, when selecting tooth knurling, it must be turned to φ19.8mm first. The surface roughness must reach Ra3.2 to avoid residual knife marks affecting embossing.
Fatal details: If the clamping is not firm, the knurling pressure may cause the workpiece to move, which may cause texture dislocation at the least and splash and injure people at the worst.
Step 2 – Tool Centering
The key to life and death: Eliminate axial twisting force
1.Installation tool: Select a straight/net knurled wheel that matches the pattern, clean the T-slot of the tool holder and lock the tool.
2.Centering calibration:
- Method 1 (precise): Move the tailstock center to the knurled wheel position, adjust the tool holder height so that the roller groove and the center cone surface are symmetrical.
- Method 2 (quick): Lightly apply blue oil on the surface of the workpiece, manually turn the spindle to make the roller pass through, and observe whether the oil film scratches are uniform.
3.Angle adjustment: The double-wheel knurling tool must ensure that the axes of the two rollers are parallel to the spindle, and use a feeler gauge to check the gap difference on both sides ≤0.03mm.
Lesson learned from blood and tears: When the center deviation is >0.3mm, the knurled wheel will break the teeth when it is subjected to force on one side, and the flying fragments can penetrate the protective cover!
Step 3 – Initial contact and pressing
Decisive moment: Breaking through the material yield point
- Contact verification: Move the large slide plate so that the roller touches the workpiece lightly, leaving a continuous fine line mark on the surface (no discontinuity).
- Violent pressing:
- Hold the handle of the small slide plate in your right hand and feed horizontally in one continuous action (no segmented pressing!)
- Pressing depth = 1/3 of the knurling tooth height (for example: if the tooth depth is 0.4mm, press 0.13-0.2mm), and you should hear a “squeaking” plastic deformation sound.
- Slip remedy: If slip marks have appeared, retract the tool immediately, reduce the workpiece by 0.2mm, and then redo this step.
Physical principle: Metal produces lattice slip at the moment of rolling, and hesitation will cause repeated slipping to form “staggered lines”.
Step 4 – Perform knurling
Process control: thermal management + uniform feed
| Parameter type | Cast iron/mild steel | Stainless steel/alloy steel | Brass/aluminum alloy |
|---|---|---|---|
| Spindle speed (rpm) | 60-100 | 40-80 | 100-150 |
| Feed rate (mm/rev) | 0.8-1.2 | 0.5-0.8 | 1.0-1.5 |
| Coolant type | Emulsion (concentration 8-10%) | Sulfurized cutting oil | Kerosene + engine oil mixture |
Operation points:
- First start the coolant pump and aim at the rolling area to form a flowing oil film.
- Automatic longitudinal feed is used, and manual feed is prohibited (speed fluctuations cause uneven texture).
- Observe the shape of iron chips: Normally, it should be short silver chips. If long blue-purple chips appear, it means the speed is too high!
Thermal runaway warning: Without cooling, the temperature of the rolling area can reach more than 600℃, which may change the hardness of the material or anneal the roller!
Step 5 – Exit and check
Final quality inspection: Eliminate secondary rolling
Exit tips: First quickly exit horizontally by more than 0.5mm, then move away longitudinally to avoid the knurling wheel from scratching the formed texture.
Defect diagnosis table:
| Defect phenomenon | Cause | Solution |
|---|---|---|
| Texture blur (double shadow) | Secondary rolling caused by insufficient first press-in | Scrap and redo, increase initial press-in amount |
| Local no pattern | Roller is blocked or insufficiently cooled and sticky | Use a copper wire brush to clean the roller tooth groove |
| Fish scale burrs | Material plasticity is too high or feed too fast | Reduce the speed by 20% and use rapeseed oil for cooling |
Ultimate inspection: Wear canvas gloves to rub the knurled surface, and you should feel uniform resistance and no snagging. Use a three-coordinate measuring machine to detect that the pattern depth difference is ≤0.05mm.
Practical case analysis: Creating an “absolutely reliable” grip for professional diving flashlights
Challenge: A well-known diving equipment company encountered serious problems with its flagship flashlight. Its smooth anodized aluminum alloy shell and knob became extremely slippery when wearing gloves or covered with mud underwater, making it difficult or even dangerous to operate, causing strong dissatisfaction among users and threatening the brand’s reputation.
Root of the problem:
- Design deviation: Excessive pursuit of minimalist aesthetics, ignoring the actual grip needs in slippery, gloved environments.
- Ineffective remedy: The shallow, fine knurling (high TPI) added earlier was easily blocked in underwater muddy environments, and became more slippery.
LS solution:
1.Redefined knurling: Abandon high TPI fine knurling and adopt low TPI rough diamond knurling (Diamond Knurl).
- Deep protrusions: Penetrate the glove/mud layer to provide direct contact.
- Wide grooves: Facilitate the natural discharge of mud and sand by water flow or operation (“self-cleaning”).
2.Key process optimization:
- Precision CNC control: Adjust the speed and feed to ensure clear and stable texture.
- High-pressure cooling system: Special cutting fluid strongly dissipates heat, lubricates, and removes chips, protects the workpiece and texture, and ensures the quality of subsequent anodizing.
- Strengthen tooling support: Prevents the aluminum alloy barrel from deforming under high pressure.
3.Real environment testing: A variety of TPI samples are made, and divers test the switch knob operation in a real environment (bare hands, different gloves, mud and sand). Finally, the optimal TPI solution is selected based on the feel, grip and mud removal effect.
Results:
- User feedback reversal: The new grip is praised by divers as a “tactical grip”, providing “absolutely reliable” grip in bare hands, thick gloves and mud and sand environments, and easy and precise operation.
- Significant commercial value:
- The return rate due to grip problems plummeted by 90%.
- Product sales increased by about 40% against the trend, and “professional and reliable” became the core selling point.
- Customers use the knurling designed by LS as a standard and apply it to their entire diving equipment product line to enhance the brand image.
Core inspiration:
Knurling is far from a simple decoration or process. It is a key human-machine interface that directly affects the function, safety and experience of the product in extreme environments. The value of LS lies in: deeply understanding the limits of materials and processes and the final use scenarios, proactively discovering the root causes of problems, and providing engineering solutions that truly solve the core pain points. Upgrading “decorative knurling” to “tactical knurling”, successfully saving the product and rebuilding trust, is the perfect embodiment of this concept.
FAQ – Answers to your more questions about knurling
1. What is the difference between knurling and turning?
Knurling and turning are two completely different metalworking processes: turning is the use of a turning tool to cut material from a rotating workpiece to change its shape, size or obtain a smooth surface, which is a cutting process; while knurling is the use of a knurling wheel or knurling tool with a specific pattern to apply huge pressure on the surface of the rotating workpiece, and to cause plastic deformation of the material through extrusion, thereby forming a raised or recessed pattern (such as straight grain, mesh grain). It is a chipless cold extrusion molding process and does not remove material.
2. What is the main purpose of knurling?
The main purpose of knurling is to increase the friction of the workpiece surface and improve the grip to prevent slipping. It is commonly seen on the surface of parts that require manual operation or gripping, such as handles, knobs, adjustment screws, tool grips, measuring tool sleeves, etc.; secondly, it is also used for decorative purposes to beautify the appearance of the product; sometimes it is also used for press-fit positioning or increasing the matching diameter in precision matching.
3. Can I knurl any material?
Not all materials are suitable for knurling. Knurling is most suitable for materials with a certain degree of ductility and toughness, such as low-carbon steel, medium-carbon steel, stainless steel, aluminum, brass, bronze, etc.; for hard and brittle materials (such as high-carbon steel, hardened steel, cast iron, cemented carbide) or materials with extremely poor ductility (such as some hard plastics and ceramics), knurling is prone to cracking, peeling or ineffective plastic deformation, so it is not suitable or the effect is very poor. Forced knurling will damage the workpiece or the knurling tool.
Conclusion
The knurling process may seem simple, but it embodies deep insights into material science, mechanics, and ergonomics. A perfect knurling is a harmonious unity of functional practicality and visual beauty, and it is also a key symbol of ordinary parts moving towards professional-grade quality. It silently proves that in the field of precision manufacturing, the carving of details often determines the final success or failure.
- Does your product need to provide absolutely reliable and uncompromised grip at key contact points?
- Do you expect to significantly improve the texture and value perception of your product through unique and exquisite metal textures?
Don’t let knurling become a shortcoming in your design. Contact the LS expert team now! We not only provide high-precision CNC machining services, but also provide professional advice for you to optimize these key functional features. Upload your design and get a detailed quote and free manufacturability analysis report immediately!
📞 Phone: +86 185 6675 9667
📧 Email:info@longshengmfg.com
🌐Website:https://www.longshengmfg.com/
Disclaimer
The content appearing on this webpage is for informational purposes only. LS makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through LS’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please contact to our for more information.
Team LS
This article was written by various LS contributors. LS is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding,metal stamping and more.
