How To How to design a folding knife?

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Liosha

Joined
Oct 29, 2022
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Hello everyone! I'm just a usual knife guy, and drawing another knife, got a complex question: where and how to design a folding knife? Like, to be more specific, I wanna know some simple programs for doing it and some basic stuff I need to know to draw a knife that'll be able to exist.
 
Draw something that looks close, cut out your patterns, line up the pivot pins, and see if it folds properly.

If my own experience is anything to go by, you're going to have trouble getting the point of your blade to fit inside the handle, and locating your blade stop is going to take some work.

I'm sure there are computer programs like Solidworks that will allow you to do prototyping, but they cost a lot.

Unless you know a machine shop that will allow you to borrow some computer time, your best bet for the first couple of attempts might just be old-fashioned pencil and paper.
 
As said above but with some other thoughts, the final drawing (can use CAD) is a result of building a model, because a drawing can't tell you if it will actually work.
- Draw the knife
- Make a model of it out of wood or aluminum for the blade and handle, with a pivot pin and a blade stop pin, and a backspacer. Now you can check the ergonomics and adjust the design as needed.
- now what type of opening mechanism do you want and how will that affect the blade shape? Flipper, thumbstud, opening hole etc. Tinker until you get something that works well.
- next consider the scales and/or bolsters, to figure out how thick you want the final product to be.
- also relevant to thickness, will you be using washers or bearings at the pivot? If bearings, will you need to mill recesses for them into the liners? You need to figure this out to know the final dimensions of the blade stop and spacers or backspacer and pivot.
- now consider clip design and placement, since that will impact ergonomics.

- now the heart of the design issue: the lock. The lock is all about precise Geometry. You should figure out everything else first because this is the trickiest part. Button lock, liner lock, compression lock, frame lock, axis lock, other . . . Each has an impact on the design of the blade tang, whether a stop pin is needed, the minimum handle thickness necessary, and ergonomics for ease of use. . . . unless it's a slipjoint, in which case it's 3 times more complicated and you'll need to watch at least a dozen hours of YouTube videos!

now make the knife again with the actual blade and liner/handle scale thickness you want, and folder parts like washers/ bearings and pivot and spacers and clips etc. You will probably end up changing several measurements in the process.

once it is perfect, take it apart and make a drawing of it in CAD with the precise measurements of the final product. Now you can send it to a maker to have it made!
 
fishface5 said:
As said above but with some other thoughts, the final drawing (can use CAD) is a result of building a model, because a drawing can't tell you if it will actually work.
- Draw the knife
- Make a model of it out of wood or aluminum for the blade and handle, with a pivot pin and a blade stop pin, and a backspacer. Now you can check the ergonomics and adjust the design as needed.
- now what type of opening mechanism do you want and how will that affect the blade shape? Flipper, thumbstud, opening hole etc. Tinker until you get something that works well.
- next consider the scales and/or bolsters, to figure out how thick you want the final product to be.
- also relevant to thickness, will you be using washers or bearings at the pivot? If bearings, will you need to mill recesses for them into the liners? You need to figure this out to know the final dimensions of the blade stop and spacers or backspacer and pivot.
- now consider clip design and placement, since that will impact ergonomics.

- now the heart of the design issue: the lock. The lock is all about precise Geometry. You should figure out everything else first because this is the trickiest part. Button lock, liner lock, compression lock, frame lock, axis lock, other . . . Each has an impact on the design of the blade tang, whether a stop pin is needed, the minimum handle thickness necessary, and ergonomics for ease of use. . . . unless it's a slipjoint, in which case it's 3 times more complicated and you'll need to watch at least a dozen hours of YouTube videos!

now make the knife again with the actual blade and liner/handle scale thickness you want, and folder parts like washers/ bearings and pivot and spacers and clips etc. You will probably end up changing several measurements in the process.

once it is perfect, take it apart and make a drawing of it in CAD with the precise measurements of the final product. Now you can send it to a maker to have it made!
Click to expand...
actually, a drawing on paper can definitely be precise enough to tell you if your pattern will work or not. So that's where I start. Pencil, paper, eraser, compass and light table is all I use. Then an aluminum template if the plan is to make more than one
 
Well true I should have been more specific: "as a newbie, a drawing alone should not be relied upon to know if it will result in the finished product you intended." Certainly someone with experience studying and practicing knife design can rely on that experience in their later designs on paper. Or someone already experienced 8n mechanical design. But in the beginning, making a mock-up can reveal lots of issues. Although many of these could be circumvented by taking a knife with a design close to what you want, getting the measurements from that, and then modifying the handle and blade shapes.
 
there are a lot of different processes a person can develop to get to where they want to be.
The reason I mentioned paper models is because that's the process I use, and the reason why is because it doesn't require much of anything shop-wise and I started designing folders before I had much in the way of tools.
The trick is to not try and design everything at once. I start with a relatively basic idea, ensuring the blade is around .5" to 1" shorter than the handle, to make up space for the mechanism, and go from there.
I trace the blade shape with the light table and cut it out, that way I can start articulating it and figuring out where the pivot needs to be and then start drafting the handle around it. Usually using a pin or whatever.
There's lots of back and forth to get things nailed down, which is why I like doing the paper model first. Once it's all figured out, I glue the final paper tracings to the materials and go for it. I've only made 3 folders myself, but I've designed plenty of knives for others who have the experience to make the knife function properly- which is a whole other thing!
Man, it's tricky to get a folder to work right. But an accurate pattern really helps- the more accurate the better
 
fishface5 said:
As said above but with some other thoughts, the final drawing (can use CAD) is a result of building a model, because a drawing can't tell you if it will actually work.
- Draw the knife
- Make a model of it out of wood or aluminum for the blade and handle, with a pivot pin and a blade stop pin, and a backspacer. Now you can check the ergonomics and adjust the design as needed.
- now what type of opening mechanism do you want and how will that affect the blade shape? Flipper, thumbstud, opening hole etc. Tinker until you get something that works well.
- next consider the scales and/or bolsters, to figure out how thick you want the final product to be.
- also relevant to thickness, will you be using washers or bearings at the pivot? If bearings, will you need to mill recesses for them into the liners? You need to figure this out to know the final dimensions of the blade stop and spacers or backspacer and pivot.
- now consider clip design and placement, since that will impact ergonomics.

- now the heart of the design issue: the lock. The lock is all about precise Geometry. You should figure out everything else first because this is the trickiest part. Button lock, liner lock, compression lock, frame lock, axis lock, other . . . Each has an impact on the design of the blade tang, whether a stop pin is needed, the minimum handle thickness necessary, and ergonomics for ease of use. . . . unless it's a slipjoint, in which case it's 3 times more complicated and you'll need to watch at least a dozen hours of YouTube videos!

now make the knife again with the actual blade and liner/handle scale thickness you want, and folder parts like washers/ bearings and pivot and spacers and clips etc. You will probably end up changing several measurements in the process.

once it is perfect, take it apart and make a drawing of it in CAD with the precise measurements of the final product. Now you can send it to a maker to have it made!
Click to expand...

^^^ GOOD INFO.

I'll add, as a maker (fixed blades)
Having the knife/model in hand is worth More than one in the drawing, or in CAD.
The feel can be extremely different making a subtle change.
I'll grind off .010" in a place in order to get the feel I want. That's just a couple hair's thick. Visually unnoticeable, but it's important.

You are Never going to learn or understand your design until you have an Actual prototype. Period.

So all the drawings on CAD or whatever is Just basically equivalent to drawing on the back of a beer napkin.
;)
 
Liosha said:
Hello everyone! I'm just a usual knife guy, and drawing another knife, got a complex question: where and how to design a folding knife? Like, to be more specific, I wanna know some simple programs for doing it and some basic stuff I need to know to draw a knife that'll be able to exist.
Click to expand...
GEt the books

Terzuola for liner locks



slipjoints
frame locks
and so on, try the google there are some tried and true books
 
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