Hey folks, let’s cut to the chase right up front—if you’ve ever stared at a CNC turning machine in your shop and wondered if it can do more than just spin bars and turn smooth shafts, you’re not alone. I’ve been selling CNC turning machines for over a decade now, and this question is probably the most common one I get from new machinists, small shop owners, and even guys who’ve been running manual lathes for 20 years. The short answer? Yeah, it totally can. But there’s a lot more to knurling on a CNC turner than just slapping a tool in the holder and hitting cycle start—so let’s break this down like we’re chatting over a shop coffee break, no boring engineering jargon that makes your eyes glaze over. CNC Turning Machine
First off, let’s make sure we’re all on the same page about what knurling actually is, because there’s a ton of misinformation floating around. Knurling’s that diamond or straight-patterned texture you see on stuff like wrench handles, screwdriver grips, bicycle pedals, or even the base of a bolt you actually want to grip. It’s not just “putting lines on metal”—it’s a metal forming process, not cutting, wait no, hold on, some people argue that. Wait, no, there’s two types of knurling: form knurling, where you press a hardened roller into the metal to push up the texture, and cut knurling, where you actually shave away material to make the lines. And that’s where the whole “can a CNC turning machine do this” debate starts.
Back when I was first getting into this business, I used to see guys stick a manual knurling tool on a manual lathe, and it’d work… kind of. But you’d get weird overlapping patterns, or the metal would gall, or you’d have to stop halfway and adjust the pressure, which is garbage if you’re running production. Then CNC turning machines blew up in small shops in the early 2010s, and suddenly people started asking if they could ditch those old manual knurling stands. Let’s get this straight: a standard 2-axis CNC turning machine—you know, the ones that spin the part on the main spindle and move a tool along X and Z—can absolutely handle form knurling, which is the most common type for industrial parts. Cut knurling works too, but it’s way trickier, and most shops don’t bother with it unless they have a super specific part requirement.
Here’s why CNC is a game-changer for knurling, compared to manual lathes. On a manual lathe, you have to hand-crank the cross-slide (that’s the X-axis, for the new guys) while the part spins, which means you’re dealing with inconsistent spindle speed, uneven feed rates, and no way to repeat the exact pattern every single time. On a CNC turning machine? You program it to hold a dead-spindle speed, set a specific feed rate (like inches per revolution, not per minute, which is way better for knurling), and push the knurling roller in exactly the right depth, with no human error. I’ve seen shops go from making 10 knurled parts a day manually to 500 a day on a CNC turner, with zero scrap from messed-up patterns.
But wait, before you go run out and try this on your machine, there are a few gotchas that every machinist I work with (and sell machines to) has learned the hard way. Let’s talk tooling first. You can’t use just any old knurling tool in a CNC holder. Form knurling rollers need to be hardened—like, HRC 60 or higher hardened—because you’re pressing them into the work surface, not cutting. And they have to be centered perfectly on the X-axis line, not tilted at an angle, otherwise you’ll get a lopsided pattern. Also, you need to make sure the toolholder has enough rigidity. If your CNC turning machine’s toolholder is flimsy (some cheapo ones from the discount store have too much flex), the roller will bounce as it presses into the metal, leaving a weird wavy texture. I always tell customers to spring for a solid carbide or steel toolholder with minimal overhang—overhang is the enemy here, because more overhang = more flex.
Next up, spindle speed and feed rate—don’t just use the same numbers you’d use for turning a shaft. For form knurling on a CNC turning machine, you want a lower spindle speed than you’d think. Like, way lower. I’ve seen guys set their spindle to 1000 RPM because that’s what they use for aluminum turning, and it ends up melting the soft metal, or making the roller skip across the surface. For most materials—aluminum, steel, brass, even plastic—you’re looking at spindle speeds between 50 RPM and 200 RPM. And feed rate? This is the big one. Feed rate for knurling has to be tied to the pitch of the knurling roller. If your roller has a 1mm pitch, your feed rate per revolution has to match that pitch exactly. If you go too fast, the pattern will overlap on itself; too slow, and you’ll get gaps or a rough finish. CNC turning machines let you lock that feed rate in perfectly, which is why they’re so much better for this than manual lathes.
Wait, what about part material? Not all stuff knurls the same. Soft metals like aluminum and low-carbon steel are a breeze—they form nicely under the roller, no issues. Brass is even easier, it’s like knurling butter. But hard metals, like stainless steel or titanium? You’ve got to crank up the pressure on the roller, and you might have to make two or three passes instead of one. A lot of new machinists try to do it in one shot, and they either break the roller or scratch the part. Our customers with CNC turning machines that have enough torque (big shout-out to the 10hp and up models) handle hard metal knurling all day long, no problem. And don’t forget about diameter—if you’re knurling a small part, like a 10mm bolt base, you have to calculate the “knurl diameter” correctly. The actual diameter after knurling will be a tiny bit larger than the original, so you need to account for that in your program, otherwise the part won’t fit when you’re done. This is another thing that’s way easier on a CNC than manual—you can plug that compensation number right into the G-code, no math on the fly.
Let’s talk about common mistakes I see people make, because that’s where the frustration comes in. First, they don’t clean the part before knurling. If there’s oil, rust, or shavings on the bar stock, the roller will skip, or the pattern will be uneven. Second, they set the depth too deep too fast. Remember, form knurling is metal forming—you don’t want to push the roller in 0.5mm in one pass, you want to do 0.1mm, wait for the spindle to make a full revolution, then another 0.1mm, until you get the texture you need. Third, they forget to reverse the direction of the spindle when they’re done? Wait no, that’s for some manual stuff. On CNC, you just retract the X-axis slowly, right? If you yank the tool away too fast, you’ll scratch the knurled surface. Fourth, and this is a big one—they use a live tool? Wait, hold on, no, wait. Wait a second, I’ve had customers ask if they need a live tool CNC turning machine to knurl. Wait, that’s a myth! No, live tools are for milling, drilling, off-center features. Knurling is done on the main turning axis, with a standard static toolholder. Oh my gosh, I can’t tell you how many times I’ve corrected that. You don’t need a live tool for knurling. That’s a huge misconception. A basic 2-axis CNC turning machine with static toolholders works perfectly. Live tools are great if you also need to do side milling or cross-drilling, but they’re not required for knurling. That’s the kind of misinformation that makes guys waste money on a machine they don’t need.
Another thing: production runs. If you’re making 100,000 knurled parts, a CNC turning machine is non-negotiable. On a manual lathe, you’d have to reset the feed rate every time, adjust the tool, and you’d get about 50% scrap from messed-up patterns. On a CNC, you run the program once, and it repeats exactly for every part. We had a customer a couple years back making bicycle handlebar grips for a big brand—they were using a manual lathe, getting 200 parts a day, 10% scrap. They bought our 8-axis CNC turning machine, and now they’re doing 2,000 parts a day, scrap rate less than 1%. That’s the kind of difference this makes.
But wait, is there a time when you shouldn’t use a CNC turning machine for knurling? Maybe if you’re making a custom one-off part, like a special tool handle for a one-person job. Then a manual lathe with a knurling stand is fine, no need to fire up the CNC, waste time programming. But if you’re doing anything more than a handful of parts, CNC is the way to go. Also, if you need a super precise pattern—like for a medical part, where the knurl has to be exact for a grip that goes into a human body—CNC is the only way to get the consistency you need.
Let’s get into the nitty-gritty of how it works step-by-step, like I’d walk a new operator through it. First, load your bar stock into the CNC turning machine, turn on the coolant (super important—coolant keeps the roller from overheating, reduces galling, makes the finish better). Next, program your G-code: start by turning the spindle on at your desired RPM, move the X-axis to the starting position, then feed the roller towards the part at your calculated feed rate. You do a light first pass, check the texture, adjust the depth if needed, then do the remaining passes. Once you’re done, retract the X-axis slowly, stop the spindle, and eject the part. It’s that simple, and CNC automates every step so you don’t have to stand there holding the tool for 10 minutes per part.
Now, I know some of you are out there thinking, “Wait, what about if my CNC turning machine has a bar feeder? Can I run knurled parts unattended?” Absolutely. A lot of our customers run overnight with bar feeders, making hundreds of knurled parts while they’re gone. The CNC machine doesn’t get tired, doesn’t get bored, doesn’t mess up the feed rate—so unattended production is totally feasible. You just have to make sure your tooling is good enough, and your program is solid, which is no problem if you work with someone that knows knurling on CNC.
Let’s address the elephant in the room: why some people say you can’t knurl on a CNC turning machine. Most of the time, that’s because they tried it on a cheap, old CNC machine that doesn’t have enough torque, or they used crummy tooling, or they tried to run it at too high a speed. I’ve seen customers come to me with beat-up 1990s CNC machines that could barely hold a consistent RPM, and they tried knurling and it was garbage. But a modern CNC turning machine—even a mid-range one from our line—has enough rigidity, torque, and control to do knurling as well as any manual lathe, just way faster and better.
Also, let’s talk about post-processing. Knurled parts on a CNC turning machine barely need any finish work. Manual knurling often leaves burrs or uneven edges that you have to file down, but CNC knurling is consistent, so you just wipe it off with a rag and it’s ready for finishing, plating, or assembly. That’s another time saver.
Now, if you’re a shop owner or machinist reading this, and you’re thinking about adding knurling to your CNC turning machine capabilities, here’s my quick checklist: 1) Make sure your machine has at least 5hp of spindle torque for most materials, 10hp if you’re doing stainless or titanium. 2) Buy quality form knurling rollers (not the cheap ones off Amazon that wear out after 10 parts). 3) Get solid toolholders with minimal overhang. 4) Program for low spindle speed, matching feed rate to roller pitch, and gradual depth passes. 5) Don’t forget coolant—seriously, that’s the #1 overlooked thing that ruins knurling finishes.
And before I wrap this up, let’s be clear: if you’re looking to upgrade your shop’s capabilities, or you’re in the market for a CNC turning machine that can do turning, milling, drilling, AND knurling, we’re here to help. We work with small shops, big OEMs, custom job shops, everyone in between, and we’ve helped dozens of customers set up knurling on their CNC turning machines without any headaches. No weird hoops, no overpriced add-ons, just straight talk about what works.
So to circle back to the original question: Can a CNC turning machine be used for knurling? 100% yes. It’s not just possible—it’s way better than manual knurling for any production run over a few parts, it’s more consistent, faster, and reduces scrap. The only time it’s not the right call is when you’re making a one-off part, or you’re using outdated, underpowered equipment.
If you’re ready to talk about what kind of CNC turning machine would work for your knurling needs, or you have questions about tooling, programming, or anything else related to this, reach out. We’re here to help you make your shop more productive, no BS.
CNC Drilling Machine References
- Metal Forming Technology Handbook, Society of Manufacturing Engineers, 2019
- CNC Turning Operations Guide, Haas Automation, 2022
- Machining Data Handbook, 7th Edition, McGraw-Hill, 2020
- Practical Knurling Techniques for CNC Lathes, Modern Machine Shop, 2021
Jiangsu Xuanman Intelligent Equipment Co., Ltd.
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