[Colleen] struggled with using a chef’s knife to cut a variety of foods while suffering from arthritis in her wrist and hand. There are knives aimed at people with special needs, but nothing suitable for serious work like [Colleen]’s professional duties in a commercial kitchen.
As a result, the IATP (Illinois Assistive Technology Program) created the Adaptive Chef’s Knife. Unlike existing offerings, it has a high-quality blade and is ergonomically designed so that the user can leverage their forearm while maintaining control.
The handle is durable, stands up to commercial kitchen use, and is molded to the same standards as off-the-shelf knife handles. That means it’s cast from FDA-approved materials and has a clean, non-porous surface. The pattern visible in the handle is a 3D printed “skeleton” over which resin is molded.
Interested? The IATP Maker Program makes assistive devices available to Illinois residents free of charge (though donations in suggested amounts are encouraged for those who can pay) but the plans and directions are freely available to anyone who wishes to roll their own.
Assistive technology doesn’t need to be over-engineered or frankly even maximally efficient in how it addresses a problem. Small changes can be all that’s needed to give people meaningful control over the things in their lives in a healthy way. Some great examples are are this magnetic spoon holder, or simple printed additions to IKEA furnishings.
better to take a sharper knive or an ultra sonic. the one which is pictured looks like an add-on
While i generally agree, most people dont know how to keep a knife sharp. The ones in the kitchen are typically some kind of steel, so they dont keep as well or as sharp as the knives that rust.
I know how to sharpen knives, i have several dry/wet stones and a sharpening steel as well, but i dont bother sharpening them every time i use them (something that might also be a hassle for someone with arthritis), i just push a little harder, until the blade starts making dents in the tomato instead of piercing the skin. I think this is a reasonable solution for normal people (with arthritis).
I also don’t sharpen each time, but as you say I keep going with the progressive difficulty and when the knife dents instead of cuts- then I sharpen
There’s steel knives and ceramic knives.
For steel knives, you have stainless steel and carbon steel. Stainless doesn’t rust. Carbon steel rusts.
Most modern knives are stainless steel. They can hold an edge, but the steel itself is tougher – it is difficult to get a good edge on them with regular sharpening stones. I’ve gone to using diamond stones to sharpen knives and scissors. Carbon steel is an absolute breeze with them, and stainless becomes much easier.
The difficulty with regular knives and arthritis is the grip, not the leverage. To use a regular knife to cut vegetables, you have to work with your wrist bent to get the knife edge to be parallel to the table. If you’ve got arthritis, that can be painful to the point of impossible. The upright grip on the knife presented here lets you leave your hands and wrists in the most natural position while still getting the knife edge parallel to the table. The upright grip is also easier to hold in arthritic fingers. Those are the gains here, not the leverage.
The repair cafe I help out in has recently started offering knife and scissor sharpening, specifically because few people have the knowledge or the tools to do a good job themselves. I’ve had people tell me that they simply buy cheap knives and throw them away and buy new ones when the old ones get dull. They simply do not know how to sharpen knives – and these are older folks, not kids.
It may depend on whether I’m slicing or chopping, but I think my wrist isn’t usually bent, my index finger is straight along the spine/back of the blade with my other fingers wrapped around the handle. The ergo handle here seems like it’s chopping-only, if I am imagining it right.
I think it doesn’t help that knife sharpening setups with good repeatability by angle control seem to be a weirdly recent innovation. Most people are aware of flat stones and hones and those sharpeners with the slot, but not things like angled-rod sharpeners.
The stones I use are actually intended for use with a sharpening system. I use them flat on the workbench just like a regular whetstone. The sharpening system rigs all look too poorly made until you get to the ones that cost hundreds of dollars. I made a little wooden holder that clamps to the workbench.
The sharpening systems don’t look like they’d be good for scissors (though maybe they can and I just don’t know how.) I can do scissors by hand on the flat stones.
The lack of leverage increases the grip force required, adding arthritis pain. As for steel, good knives are Martensitic stainless (400 series). They don’t rust like mild steel but do corrode with acids or alkali which both mark the surface and chemically blunt the edge. If you have a good knife, it stays sharper longer if you wash it immediately after cutting many foods, especially tomato. While crevice corrosion is worst, the blade edge isolation also facilitates corrosion even when this would be much slower on a flat surface. Test for yourself. Your kitchen knives should be ferromagnetic, far more than your forks, which are typically austenitic (300 series) stainless.
Nice to meet another Assistive Technology expert! Great that you are sharing your insights.
Hi! I designed and built this. The knife tang was purchased from a reputable source and was razor sharp when we built this functional
prototype.
Agreed. A sharp knife is a safe knife. And, I believe the design of this knife is more aimed at wrist and finger articulation relief. Repetitive motion, especially concentrated in the fingers, wrist and forearm can quickly inflame arthritic joints. Hope this helps her at work.
You take every chance to make it about your agenda, huh?
i have an agenda. and it is to inform all here…. That their prints don’t need to look so stringy and blob ridden. Man, tune that retraction and avoid crossing perimeters. That thing is one poor looking print. :-D
also confused as to why you would print something with so many holes that requires cleaning out of food particulate. at least put an outer shell on the thing. GROSS! :-p
love to see easy and inexpensive things to help those who require assistance.
having said that, this seems like it would decrease accuracy by quite a lot. also looks flat out like it gives more leverage for stabbing than slicing. don’t forget, ya gotta hold the item in place with the other hand.
I am a proponent of keeping a knife sharp. There is a disconnect with people taking personal responsibility for the condition of their tools. A tool in proper working order is a safer tool, be it a saw, knife, car, or anything else we use.
Keep your tools in a safe working order please. I sharpen knives for my family too… it is sometimes painful to watch how others use knives. it’s usually in some way that is dangerous or not how the device is intended. Prime example of this is not sliding the knife forward on the down stroke instead just forcing it straight downward as if it were a lightsaber or chainsaw.
simple whetstones can be had at your local asian market for under 15 dollars. Double sided, effective. Not the best edge or fanciest, but they will get the job done in short order. If ya wanna get all fancy get a finishing stone like a blue stone.
You can get a set of six diamond stones for around 20 dollars from Amazon. 120 to 3000 grit. Add a leather strop and some polishing compound and you are all set. The diamond stones work better than the double sided industrial grit stones.
Howdy! I built this knife and we went through a few versions prior to this. We printed plastic versions and gathered feedback, the. Based this design around that feedback. I would consider this a functional prototype more than a finished product, but the process is documented and available for others to improve upon!
P.S. I worked in the food industry for just under a decade, and actually sliced the limes on that cutting board. Accuracy wasn’t bad, assuming the other hand is properly situated.
Thanks for all the comments! We continually improve these products based on feedback!
This is awesome! It’s great to learn programs like IATP exist, which provide an avenue for makers to give back to their communities.
Just how much “leverage” do you need? You’re not slicing wood. And it looks like the linear fulcrum(tip) to lever distance hasn’t really changed much, mechanically it’s about the same, with less rotational control.
Might come in handy when you have the need to use it as a novel combat knife……. but even then…
As others have said, it doesn’t look like this is really about leverage. It’s about wrist position and minimising pressure on joints. Think of it as the knife equivalent of an ergonomic keyboard.
Interesting.
I could use a tool to hold whatever I’m cutting.
I have severe hypermobility .
Claw grip? Forget about it!
The comments here are just unreal. People mansplaining left and right about how things work in a kitchen, who apparently didn’t even bother to read two sentences in: “[Colleen]’s professional duties in a commercial kitchen.”
Somehow, I get the impression that someone who has professional duties in a commercial kitchen, and has managed to survive long enough to get arthritis, might know a thing or two more about their specific use case than some random jackwagon on the Internet.
From the project page explaining the background of the knife:
“The purpose of the design is to reduce the joint tension and pain experienced at the wrist during cutting tasks.”
https://iatpmakers.org/adaptive-chef-knife/
Could it be an advantage to have the support resting on top of the arm, using the handle as a fulcrum?
I needed a few seconds to realize the photo didn’t show a bladed tonfa.