How can I design a custom ergonomic knife handle?

[Steel_Magnet77]

I will say that I had mentioned that the article was finding the best size based on COMFORT, not greatest grip strength... I don't know which is more relevant but yeah.

 

[billf]

I applaud you for your interest….

Maximum grip strength fatigues quickly, so that is not relevant in anything more than very brief (say 5 second) uses - again, perhaps in a life threatening “need to stab a grizzly bear “ situation. There ARE handle features that will maximize ability to apply full grip strength…but they will be counterproductive in virtually any other situation. Think sword vs kitchen knife or dagger vs scalpel

“Comfort” in regard to repetitively manipulating a cylindrical machine handle is A) subjective and B) not relevant to how one uses a knife (multi-positional tool)

I used a scalpel for probably 20,000 hours in my career - probably held in in 4 positions, with one the most common. Look up pictures of a scalpel and you’ll see how “simple” the handle is…..

 

[Stacy E. Apelt - Bladesmith]

Bill is mentioning one of the other comparisons I was thinking of.
I have quite a few scalpels handles in several sizes (mostly #3 and #4). They are pretty much as simple as a handle can get. 2-D, flat, sightly tapered to the front, groves on the front of the sides for dexterity control, and a round butt. For hobby work, I use the "ergonomic" plastic handles, which are a 3-D handle shaped like a Coke-bottle handle. The very early shapes from a couple thousand years ago were pretty much a small knife, similar to a caper, with a small and sharp blade. Later on, the simple shape we use today came in. For surgery and medical uses, the standard shape hasn't changed appreciably in well over a century. A scalpel handle needs to be autoclavable for most uses today, so the flat ones are what you see mostly. They do make 3-D handles in stainless that can be autoclaved.
Grp positions are various, as Bill said, but I and most folks I know use the pencil grip.
What occurred to me was they are pretty much a flat version of a simple knife handle (like a paring knife). The ones I have that my dad used in WW2 are not appreciably any different than what we use today ... except they have a one-piece blade and handle and must be sharpened by hand. Disposable blades were a luxury in the war.

Funny thing is that I started doing wood carving using scalpels ... or my pocketknife. They were always around and free. It was many years later that I got my first dedicated carving tools.

 

[JoeBusic]

I had this one in three sizes. Sold only 3 knives. One general (in the picture) and two combat style. Combat is the only use of this style of ergo handle. After over a year not sold, gave away a dozen of sizes and styles with ergo handles. Moved away from them.

 

[Lorien]

that's a pretty interesting handle, just from an aesthetic my eye wants a less practical blade shape to go with it.
I don't think it's important to always make things that are just made to work, I think it's just important to always do the work to make things.
When there's synergy to the design, it will attract attention- regardless of intended use, or even the ergonomic interface.

 

[JoeBusic]

that's a pretty interesting handle, just from an aesthetic my eye wants a less practical blade shape to go with it.

Something like this? I don't have a finished photo.

 

[Drop bear]

Result of that clay thing: https://www.bladeforums.com/threads/fixed-blades.1829548/page-268#post-22779856 post #5341 and #5342. This handle shape is comfortable for 90% of the people who have held it/used it (at least from the feedback I got).

Yeah. That was sort of my play doh idea. You could mail it to them. They form it. Bake it hard mail it back. And you have that hand swell.

Clay would probably work better.

 

[JoeBusic]

Play doh doesn't work. Indents are higher pressure parts and should be higher. When squeezed it's lower than average curvature. Tried it and got bad results. When I figured the issue, started with a thicker wooden handle and thinned slowly per feel of pressure and got what I wanted. Afterwards designed it in CAD with surfacing tools and printed prototypes. After 20-ish pieces, I got the final result.

 

[navman]

Unlike shoes, I really don't think a full on custom fit handle will work well. It limits hand placement and grip options, and if the buyer wants to re-sell the knife, now they have to be concerned with how it will fit in someone else's hand. Sometimes generalities are better than specificity.

When I used the clay to model a grip, I took the grip and still had to tune it for multiple grip angles and then changed the dimensions to fit a broader range of hands. Is it secure and comfortable, absolutely, but that took some trial and error, having various people with different sized hands grip the handle (in micarta) and provide direct feedback.

 

[Stacy E. Apelt - Bladesmith]

The only time I ever used clay was on a handle for a man with a very damaged hand (fishing trawler accident). He had no pinky finger and part of the palm missing. I made a full-tang template of the EDC knife from 1/4" wood and reduced the tang to a stick tang. Then I applied molding clay (plasticine) to it and made a hand;e like I would use for a normal knife. I then had the man hold and squeeze the handle. I removed some clay, and we repeated the molding. After a few more adjustments it fit his hand in a grip he could control. I used that as a model for the wooden handle shape on the full tang finished knife.

I do one thing on most knives to make them more ergonomic for everyone. I reduce the area just behind the ricasso in a shallow groove angled back and make a shallow finger groove. It is like a much less dramatic version of the front of Joe Busic's handle, and round that into a slight palm swell.

 

[Lorien]

Something like this? I don't have a finished photo.
View attachment 2851398

100%

 

[Steel_Magnet77]

“Comfort” in regard to repetitively manipulating a cylindrical machine handle is A) subjective and B) not relevant to how one uses a knife (multi-positional tool)

I would say that comfort might not be entirely subjective. I would guess that a cylinder is more comfortable in the hand than a hard edged rectangle box. Would you say that comfort provides more joy in use? Would you say that comfort is a big part of an ergonomic handle? Would you say that comfort creates less operator wear? Would you say that comfort reduces the risk for cumulative hand injury? Sorry for all the questions

 

[DevinT]

I would say that comfort might not be entirely subjective. I would guess that a cylinder is more comfortable in the hand than a hard edged rectangle box. Would you say that comfort provides more joy in use? Would you say that comfort is a big part of an ergonomic handle? Would you say that comfort creates less operator wear? Would you say that comfort reduces the risk for cumulative hand injury? Sorry for all the questions

People don’t buy knives based on comfort, it’s always an emotional purchase. Comfort might be part of the decision but art or hand crafted items are based on emotion.

Hoss

 

[Seedy Lot]

But comfort can create long term customers.

 

[Lorien]

^I'd swap the 'but' for 'and'.
we can have it all!

 

[Nastasiia Coval]

I guess I will take another stab at this. I can only make handles that are comfortable to my hand, and when I make a knife for someone else I am essentially guessing at what will be comfortable for them. My goal is to be able to sell knives with custom handles to fit the buyers hand in an ergonomic way. In order to do that I would need to create a process system that uses a couple measurements from the buyers hand to give me optimal handle length width and height. The overall shape and swells of the handle would be less relative and could simply be scaled. How can I design a custom ergonomic knife handle for the buyer?


p.s. Mildly sad that my other thread was killed. Not really sure why, maybe too scientific? But you can make anything scientific .

Oh wow, I really relate to what you’re saying! I once made a knife for a friend and realized just how tricky it is to get the handle right without having their actual hand in front of me. Lately, I’ve been working on a custom-fit system too — I use the palm length, base width near the thumb, and the hand’s center thickness. With those, you can start shaping a handle that feels truly ergonomic.

My last handle was actually made with a stunning piece of burl walnut wood I found in a small shop — the grain was just beautiful. I try to make my handles not only comfortable, but something you really want to touch and hold.

And I’m sorry your last thread got taken down — science and craftsmanship totally go hand in hand, especially when it’s about comfort and form. I would’ve loved to read more from you!

 

[David Mary]

Saw this super comfy handle

I see these and double cringe every time. Once for the ergos and twice for all the likes they seem to get.