What’s the Best 3D Printed Knife Sharpening Fixture? – Tom's 3D printing guides and reviews

… and is CNC Kitchen’s design still the best option? I try 8 3D printed sharpening helpers in an attempt to get my knives, chisels, and hand plane blades sharp again.

If you ask someone how you should sharpen your knives or chisels, you’ll get two kinds of answers: “Buy a Tormek” – which is the premium option, or “Just use that brick you found in your backyard!”

Both are totally valid options, but I think a middle ground, in most cases, would be a more reasonable choice. Thankfully, we have technology to create that, so I set out to try some of the most popular options for 3D printable knife sharpening fixtures and guides. Stefan from CNC Kitchen cemented the concept that you don’t need a super fancy fixture in order to keep your knives sharp, but I also need to maintain my chisels and hand plane blades, which his design is just not made for.

Surprisingly, there aren’t too many other printable designs available, so I picked and printed the five that seemed the most popular, most feature-rich or interesting in some other way. There are also helpers available for free-hand-style sharpening, so I printed some of those as well, and we’ll try all of these out

Assembly

Knife Sharpening Tool V2.1 (with video) by CNC Kitchen

Let’s start with the CNC Kitchen fixture. Immediately, it’s pretty weird to see Stefan’s design use slide-in nuts instead of threaded inserts, but this is a design from quite a while ago. The parts all have a pretty loose fit, which is appropriate for when these were designed, but printers have become so much better that I had to use my trusty adjustment tape to get the tubes to clamp down. The pivot for the grinding arm uses a pretty neat captive latch, but the locking screw for the height calls for an M4 hex head screw, which I don’t have, but that’s nothing a bit of super glue can’t hide.

I bought the exact stone set that Stefan used and a diamond stone set since that seems to be all the rage these days. The diamond stones are too large to fit in the holder, so I chucked up a regular 600 grit stone.

For the magnets, I didn’t have the exact size called for, but I had these rectangular ones that I can use in pairs. They simply slide into the base, and because the magnets attract each other in there, they stay in place pretty well.

Knife Sharpening Tool V3 by Bas

The “refined” version by Bas makes a couple of changes – the base kicks out the front feet further forwards, for a fortified foothold, and the vertical bar now fits nicely with no clamping screws needed. But while that fit got just tight enough, the slot for the M5 screw of the knife clamp is now too tight.

The stone clamp now works lengthwise, and it nicely fits the longer diamond stones, but it’s now too loose for the plastic bases of the regular stones. And instead of the captive pivot design, it’s now a print-in-place ball that is very stuck-in-place off the printer, but once you break it free and then spin it a couple of times, it runs pretty well (but so did the original design). And on the side, there is now a printed screw that holds the pivot in position – doesn’t mar up the vertical bar as much, but I’m not so sure about the longevity of the plastic thread and the screw itself.

So overall, the base is a nice upgrade over the original, and the new holder is definitely needed for the diamond stones. I’ll add those two upgrades on the original, and use it as a best of both worlds approach.

Knife Sharpening by NikNolte

The design by Nik Nolte works in much of the same fashion – I didn’t have any 15mm rods that were called for, so I just printed some. The knife rest is a separate piece on this one, so you can flip it around to sharpen chisels. I don’t know if that’s intended, but it should work.

The pivot design on this one maybe is a little overkill – the design uses 8mm rods exclusively, which I like, because they’re cheaper and and more rigid than aluminum tubes, and you might already have some flying around, and this design goes all-in with an LM8UU linear bearing for the back-and-forth motion, a pair of flange bearings to allow for tilt up and down and an extra pair of skateboard bearing for the swivel left to right. I mean, that absolutely feels extremely smooth, but I kinda doubt that it makes a difference for getting a knife sharp. The stone holder is pretty nice, too, it’s spring-loaded, so changing a stone is really quick and easy.

Knife sharpener – Wusthof whetstone by pandax

The Wüsthof stone holder by Pandax is, by far, the simplest design here. It has a large printed base and uses 10mm rods, the pivot simply is a hole to stick your rod in, and it’s specifically made for the larger free-hand-sharpening style waterstones. Not the full sized ones that you get with the little base, but for a smaller compact size that just has an unspecified fine and coarse grit on each of the sides. I bought a couple of these for like two or three bucks each, and they do work pretty well, but you have to flatten them pretty often, and that will thin them out over time. The one I used is the best one out of the ones I have, and with these simple endpieces to hold them, there is a bit of slack in there.

Knife, Scissors, Chisel & Razor Sharpener – Leading Edge System by leadingedge

The Leading Edge system claims to be literally “the only available 3D printable Knife, Scissors, Chisel, Straight Razor and tool sharpener”. It is for sure the most complex one, it calls for the most variety of fasteners and uses half a pack of threaded inserts to get going, though not the CNC Kitchen style ones, but the simpler injection molding ones, which are not very fun to work with. Like with the other fixtures, I didn’t custom-order individual screws and I’m instead using what I have at hand, and that’s ok. A couple of detail images to help with the assembly would have been nice, but overall, the parts are all designed with pretty much perfect tolerances for 3D printing. The stone holder uses a design similar to the one by Nik Nolte, but here, the use of the simpler threaded inserts caught up to the design and meant I had to glue the fixed side in place with this design as well. The pivot ball also had tolerances that were very tight, so with the ball already being glued captive into place, I tried my best reaming it out.

This Leading Edge fixture definitely took the longest to figure out how it fits together and then also took the longest to build, because it’s so modular and tries to do so many things at once. Is it worth it? Well, let’s sharpen some knives and some tools and find out.

Learnings

I had four different kinds of edges I needed to sharpen: Full-size chef’s knives, small paring knives, chisels, and hand plane blades. Every fixture can handle the knives, but I was only able to chuck up my chisels in the Nik Nolte design and in the Leading Edge, while the hand plane blade also worked on the CNC Kitchen fixture.

Stone guides

The free-hand sharping guides sound good on paper, but in practice, trying to adapt these sharpening stones into a semi-guided system didn’t work out. The guides all need the stone to sit at a very specific height, which means they’ll only work with a non-worn stone of the exact kind required or they’ll create too much of a gap between the cutting edge and the stone. Some of the fixtures were binding up as you’d slide them back and forth, but even the one that worked the best required you to simultaneously coordinate 4 competing positioning tasks or you’d end up creating a polygonal grind, nicking the cutting edge on the edge of the stone or sliding off the guide entirely. Plus, with the way these guides work, it’s impossible to sharpen the last inch of you knife’s edge that is closest to the handle.

These sharpening stones are meant for free-hand sharpening and that’s what they’re good at – the guides made the process more complicated and stressful, so my recommendation would be to instead either practice free-hand sharpening or, if you want more precision, to use one of the grinding fixtures.

Fixtures

First off, all of the fixtures work to get a sharp edge, but the differences lie in how convenient they make it to get to that point.

There were generally three weak points: The first one is the pivot mechanism, which seems to be surprisingly hard to get smooth motion out of. The CNC Kitchen pivot has limited range of motion, causing it to bind on the tip and heel of the chef’s knives. I also ended up oiling the tight ball pivot on the leading edge, and that was overall the best experience because it had the least slop and the best range of motion.

The second weak point is rigidity. The CNC Kitchen fixture was the best one here, it did the best job supporting even large chefs’ knives and is generally chunky enough to resist bouncing around when you’re sharpening. Nik Nolte’s design struggled a bit with bouncyness as well, but that might likely be because I cheaped out and used printed 15mm rods for the base.

The third one is workholding. You don’t want a large, sharp object to slide around when you are working on it. Yes, I did not have the exact magnets called for for any of the fixtures, but the super-simple Wüsthof stone holder has just three magnets and no other way of clamping a knife down, which made it hard to work with. The Leading Edge takes the lead here. The magnet base is less stable than the CNC Kitchen one, because the leading edge is overall a slimmer design, but the reversible knife clamps it includes are absolutely fantastic to use. I found a similar-looking one that fits the CNC Kitchen fixture, but it doesn’t work the same way, it only ever clamps along the knife’s spine, so it doesn’t hold very well.

For sharpening chisels and hand plane blades, the only one that’s made for that is the Leading Edge, but the included holder for that isn’t very good. It’s a little wobbly, has very little clamping surface and doesn’t provide any guidance or reference edges to keep chisels aligned straight. In a pinch, it does work though.

So which one of these should you print? If you just need something simple, the CNC Kitchen design totally does the job, though maybe drop a bit of grease into the pivot and print the upgraded base. The other fixtures all work, but the one that stands out to me is the Leading Edge. Turns out its cocky remarks about being the only system for XYZ, yeah, there’s something to it. It is a good sharpening system, but I do wish it would have received one last upgrade to modern threaded inserts, and maybe an overall bulked up design to make it a little more stable. But maybe Stefan comes out with an updated version of his fixture. I’d love to see that!

Keep on making, and I’ll see you all in the next one!

Fixtures:

CNC Kitchen v2.1 (based on Henschke )

Stone guides:

Sharpening stones from Amazon