Introduction: Folding Kitchen Knife

I had an idea to see if I could make a small thing big. As I was making dinner I pondered what smaller objects could be remade into a larger version when it hit me; Why not make a folding knife large enough to cut up my vegetables?!

Continuing a trend of questionable ideas, here's how I turned a small folding knife into a big folding knife.

Ready? Let's make!

Step 1: Supplies

I used a folding blade with a linear lock as the template for my design. This knife is very simple and was designed as a kit, making it easy to disassemble.

I then looked for the largest kitchen knife I could find, which was a 14" chef's blade.

With these 2 components I could start designing the folding kitchen knife.

Step 2: Take Things Apart

The folding knife had a few torx machine screws holding the two halves of the handles together. With the knife completely disassembled I could determine how it worked and what needed to be done to make a larger version with the chef blade.

Step 3: Scan Folding Knife Body

To scale up the knife accurately I photocopied the knife halves and the blade, along with the chef blade.

This photocopier allows me to scan and digitize the file as a PDF.

Step 4: Computer Design

I imported the PDF scan into CAD and traced the folding knife outline, then traced the chef blade.

With the knife outlines traced at the correct size I could resize the folding knife to fit the chef blade. With the handles scaled up the chef blade was checked for clearances in the folding knife body. Minor adjustments were made to the chef blade to allow a clear swing path.

The outlines were then printed on standard printer paper and printed.
You can download my folding knife PDF below.

Step 5: Print Template

Print the template on standard printer paper.

Step 6: Glue Template

Spray adhesive was used to glue the template printout to a piece of 1/4" plywood.

Step 7: Cut Plywood

Once the glue had dried completely the wood can be cut out by following the outline. A scroll saw or bandsaw will make quick work of this.

Step 8: Handle Openings

Before the lock channel is cut all the openings in the handles are drilled.

I started by drilling the opening at the end of the lock channel with a 1/2" drill bit. Then, the two halves were lined up and clamped together. Using a 1/8" bit I drilled the openings around the perimeter that would connect the two halves.

Step 9: Cut Lock Channel

After the openings were drilled the lock channel was cut. Cutting the opening at the end of the channel makes removing material in the channel much easier.

Step 10: Remove Paper Template

With all the openings and shapes cut out the paper template can be peeled off and removed. Sanding will remove any paper that remains stuck, so it's not important if there's any left stuck on.

Step 11: Steam Lock Channel

The lock channel on the small folding knife is a bent section of steel that acts like a spring and locks the blade in place when it passes the threshold in the fully open position. To mimic this action I steamed the lock channel into position.

The locking half of the handle is placed over a pot of boiling water and left to steam for a few minutes. Do not submerge wood. Next place a wedge of sacrificial wood into the lock channel to bend the wood, then continue steaming for a few more minutes. Remove wood from heat and let cool completely.

Once the wood is cool the sacrificial wedge can be removed, the channel should now stay bent allowing the lock to engage when the blade is inserted.

Step 12: Handle Standoffs

To allow space for the blade between the handles I used small strips of wood as standoffs. These standoffs were slightly thicker than the blade.

I rough cut some scrap wood to use as standoffs, making sure not the cover any of the drilled openings which would attach the two halves, and ensuring not to cover the blade path. I used regular wood glue to attach the standoffs.

The rough shape would be shaped and sanded when the handle assembly is complete.

Step 13: Mark Blade for Cutting

Using the paper templateI traced the cut lines onto the chef's blade with a marker.

To protect the blade, and myself, I covered the cutting edge of the blade with tape.

Step 14: Cut Blade

To make this chef blade fit into the profile of the folding knife the tang needed to be removed. I used a metal cutting bandsaw on a high speed to cut through the hardened steel blade, then cleaned up any burrs with emery cloth wheel and metal file.

Step 15: Drill Rotational Opening

The hardened steel knife blade is very strong, and only tough drill bits will be able to drill through. Using carbide tipped drill bits I started with a small pilot hole, then reamed the opening with larger bits until the opening was of the right diameter.

Even with heavy duty drill bits, I still ruined a couple of bits drilling through the blade.

Step 16: Assemble Pieces

The pieces can be assembled and a threaded rod is inserted as the rotational axle for the folding action.

The threaded rod bites into both the wood and the blade openings. It's not a perfect solution, but works well enough to hold the blade securely in between the wood handle halves.

Step 17: Dowel Attachments

Using wood glue on the standoffs, the two handle halves are pressed together. Wood dowels were hammered into the drilled openings to secure the two sides. Allow glue to dry completely.

Step 18: Refine Lock

After the glue was dried and I had a chance to test the locking action I noticed that some of the wood at the end of the locking channel was wearing away, making the locking sloppy. With the blade fully extended I made a small metal shim that was epoxy glued inside the end of the lock channel, this securely held the blade locked open when in use.

Step 19: Trim Attachment Dowels

Using a small hand saw I trimmed the excess length of wooden dowels holding the two halves together.

Step 20: Trim Folding Axle

Using an angle grinder the excess threaded rod was trimmed from either side of the handle.

Step 21: Sanding

Starting with a coarse grit sandpaper I removed any leftover pieces of the glued on paper template and rounded over the edges. Then switching to a finer grit sandpaper ensure a smooth and uniform finish over all surfaces of the knife.

Step 22: Wax Finish

Since this knife is for food use I went with a natural wax finish. Using a rag I rubbed the wax into the wood which gave it a nice finish.

Step 23: Flip Out and Chop!

You're all ready to bring a knife to a food fight!

This ridiculously large folding kitchen knife is ready to decimate your veggie ememies. Flick out the blade and start chopping.

Comments

author
Jake_Makes made it! (author)2015-03-09

Exact measurements?

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mikeasaurus made it! (author)mikeasaurus2015-03-11

Large.

author
Jake_Makes made it! (author)Jake_Makes2015-03-25

Bigger

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pdicapua made it! (author)2015-03-22

Beast knife! Love it bro

author
wdsims63 made it! (author)2015-03-14

Really awesome. And while your inspiration was a liner lock knife, this is technically a frame lock knife. Either way, it's totally cool and I now have something to do with my extra chef's knife that I haven't used in a while.

author
NitroRustlerDriver made it! (author)2015-03-12

Definitely going to be making one of these. I work at Leatherman Tool and everyone will get a kick out of it.

One thing about your design. On the blade lock, normally the end edge of the knife is cut/ground at an angle instead of 90º to the flat of the blade. What this does is give the locking tab a ramp to wedge against. In a perfect world, a perfect flat edge against a perfect flat edge will have no wobble, but in the rear world, it's very difficult if not impossible to make. By making the end at an angle though, the locking tab just moves until it can't anymore (wedges) and makes for no wiggle in the blade.

I hope I explained this clearly enough. Look at the end of your black knife. I bet it has an angle on it. That's how we do it at Leatherman anyway.

author
mikeasaurus made it! (author)mikeasaurus2015-03-12

Thanks for the insight. You're totally right, and I learned a lot about how linear locks work from making this. Even though I copied the design, the minutia is what separates successful commercial products.

I spent a long time refining the action, and working on the lock. Even after redoing sections it was never perfect. If I were to remake this project I would probably do the locking side from something other than wood, possible wood and metal laminated. And, as you mention, work on making sure there was less wobble factor.

Thanks for sharing your knowledge. Since you work at such a cool place I bet you have access to all the right tools to make this bigger, and better than mine (I'm never without my leathman wingman). I'd love to see your work when you're done (maybe we can duel?).

author
NitroRustlerDriver made it! (author)NitroRustlerDriver2015-03-12

I do have access to a 4kW laser cutter...

I'll probably go low-tech though like you did and build it at home. Much more fun of a process that way.

author
mikeasaurus made it! (author)mikeasaurus2015-03-12

...that laser though!

author
Dalen Brewer made it! (author)2015-03-09

I want a whole knife set. Chef, stake, bread, and a pairing knife. It would be cool to see like a spatula

author
mikeasaurus made it! (author)mikeasaurus2015-03-11

Maybe a Swiss Army variation with all the kitchen utinsels?

author
Dalen Brewer made it! (author)Dalen Brewer2015-03-12

If you were to make these and sell them on eBay i would defiantly buy one. Especially a swiss army stile one.

author
alesandrome made it! (author)2015-03-11

THIS IS SO AWESOME!

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mikeasaurus made it! (author)mikeasaurus2015-03-11

I like living dangerously. The kitchen is now the most hazardous place whit this in the arsenal.!

author
Christian Reese made it! (author)Christian Reese2015-03-12

If that's your knife, I wonder what you frying pans looks like :D

author
Newton made it! (author)2015-03-11

This is absolutely brilliant, I have to make one as well.

author
woodNfish made it! (author)2015-03-11

Okay, your over-sized knife is amusing, but it is also dangerous because the handle is too large for your hand. You can't get a good grip on it, and that makes the chance of an accident more likely.

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mikeasaurus made it! (author)mikeasaurus2015-03-11

Grip with two hands?

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lfoss made it! (author)2015-03-11

This is a great looking knife! But my friend and I are having this argument: he says your shirt is blue and white, I say it's purple and orange. Who is right?!

author
mikeasaurus made it! (author)mikeasaurus2015-03-11
author
dworley made it! (author)2015-03-10

The hidden danger of Pier 9 is that "because you can" is going to take up all your time. Also I'd sand off that wax use some polycrylic. All finishes are food safe when they cure.

author
mikeasaurus made it! (author)mikeasaurus2015-03-11

I will cut you :)

author
gravityisweak made it! (author)2015-03-09

This is just begging to be done in laser cut acrylic or similar material. What a cool idea.

author
mikeasaurus made it! (author)mikeasaurus2015-03-11

Thanks! I actually made a prototype on the laser cutter, but decided to do it by hand as it's more accessible.

The knife is gone from the kitchen now, so maybe it's time for a laser cut one?

author
xpozitron made it! (author)2015-03-10

This is quite a dedication to work that hard on a random idea like this.
I guess that knife like this will not be much practical as there would be "kitchen grime" soon stuck inside of the handle and the cleaning would be a hell...

author
mikeasaurus made it! (author)mikeasaurus2015-03-11

Extreme cutting only.

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sctirvn687 made it! (author)2015-03-10

Great job! This reminds me of a folding knife that I have.

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mikeasaurus made it! (author)mikeasaurus2015-03-11

That is a crazy knife. I like it!

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TheKnifeMakerz made it! (author)2015-03-11

this is sweet! i forged my own blade and its a clippoint but i use it like a folding sword. :)

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crank_girl made it! (author)2015-03-11

What fun! I'm definitely giving this one a go. Now who to gift it to?

author
gravityisweak made it! (author)2015-03-09

When I first saw the photo I thought someone had found a way to make really tiny realistic looking hands.

author
cdstudioNH made it! (author)cdstudioNH2015-03-10

:D

author
acoleman3 made it! (author)2015-03-10

rather comical....but if you think about it, practical at the same time. you're blade edge would be sure to not blunt over in this configuration!

author
longp2000 made it! (author)2015-03-10

That is really cool, but one caveat.

Be aware of your state and local laws about folding knives. Where I lived in Southern Alabama I was cited for carrying a folding knife over 6 inches long. It was a homemade survival knife that my Dad and I made, but the police said since it folded into an enclosure it was considered a folding knife. I had to pay a $155 dollar fine when I went to court. This was 20 years ago, but I would still be aware if you plan on carrying it on your person when you go camping or whatever.

I plan to make one of these and keep it in my kitchen.

author
acoleman3 made it! (author)acoleman32015-03-10

if you're going camping with it, toss it in your pack in the trunk. they can't cite you for what they can't see.

author
ovenmitt made it! (author)ovenmitt2015-03-10

Yes, in Georgia you need a concealed weapons permit to carry a knife above 5 inches (IIRC).

author
urbanmx made it! (author)2015-03-10

When I camp everyone get's a little "that's not a knife, this is a knife" need this to win camping!!!

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iamunique127 made it! (author)2015-03-10

I love big knives! Great job.

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Lachlan Van Vliet made it! (author)2015-03-10

glitched again

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Lachlan Van Vliet made it! (author)2015-03-10

saw it,

wanted it,

need to make it

author
Lachlan Van Vliet made it! (author)2015-03-10

saw it,

wanted it,

need to make it

author
mrandle made it! (author)2015-03-09

This would be amazing for camping too takes up less space and is sheathed basically.

author
hubbe made it! (author)2015-03-09

"That's not a folding knife - this is a folding knife!"

author
blowe7 made it! (author)2015-03-09

I want to make one to take on picnics. I hate transporting the watermelon knife.

author
MrBeta made it! (author)2015-03-09

This is ridiculous and I need one.

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tylerlund381 made it! (author)2015-03-09

Awesome idea.

author
deluges made it! (author)2015-03-09

I really like the design! Be careful not to let it get moldy when it dries though ;)

author
Wolfbane221 made it! (author)2015-03-09

That is a big frikin folding knife.

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Bio: I'm Mike and I make crazy things at Instructables HQ in San Francisco. Follow me and try a few of my projects for yourself!
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