My DIY all carbon fiber knife builds, with step-by-step pics

[liveforphysics]

I bought some carbon fiber materials to make some fairly complex parts with, and sadly realized that I was badly lacking the skills needed to make complex things.

So, I decided to try some simple things first to teach myself a bit, and trying a knife seemed like a simple and fun first try.


I know you knife building pro's are 10000x better than me, and I know my shapes I just eye-balled for the blade shapes and handles etc are nothing amazing. This was just an exercise in working with CF for me, rather than the quest for building the worlds most amazing knife.


So, I picked through some of the pics that turned out decent (all just done on my cell-phone cam ).

The first set of pics is for the thick and long bladed knife I made, which turned out to be really over-kill on blade stregnth, and kinda silly how thick it was. The second set I went with 1/2 the blade thickeness, and it still feels so rigid that flex seems almost undetectable in it, and it slices veggies and things much better with the thinner blade section.

I used my DIY CNC machine to rough-out the strip to become the blade from some 1/4" CF.

Then I ground it and wet sanded it into a shape I liked.

Then I measured up my hand vs the tang material I left, and decided how big to cut the scabs to laminate into being the handle.

Then cut them out with my CNC.

Laid them all up to make sure I was happy with how thick it would be. I used 2x2 twill weave carbon for the blade and inside area of the handle, and then used a slick 1x1 checker board weave for the outside layers of the handle. I think the design contrast is pretty slick.

I mixed up a batch of the special fancy-pants epoxy in the special ratios, and mixed it in the recomended way to avoid bubbles from getting mixed in, then coated both sides of each piece, stacked them all together on a big chunk of solid teflon, and applied weight with another big chunk of teflon.

Patiently waiting for the stack to cure well enough to go in the oven for final hardening...

Once it all cured, I started the filing and sanding process. Dry sanding the carbon was pretty bad, but wet sanding with fine grits, like 600-1000 worked very well.

Hours and hours of sanding later.... and I had something I was proud of.

Then, onto the next knife.

 

[AussieJester]

you might be getting a few calls from Jhad extremists looking to do business with you Luke they
would pass through airport security very well just tucked in your sock hahaha

Very nice result mate well done, what programs are you using with your cnc?

KiM

 

[liveforphysics]

The next week, I started another knife, this time with the thinner blade, because the first knifes blade was just way stiffer and stronger than I could ever imagine it needing to be.

Then rough ground it.

Then cut out the handle laminations, laminated them, cooked in the oven at 300f over night, and this is what it looked like.

Trimmed off the ugly with the bandsaw.

Then I started in for a few hours of file work...

Then, another few hours of wet sanding, and I had another knife I was proud of. This one just feels damn good in the hand, and I got an edge good enough on it to slice tomatoes easily, and it seems to do a pretty good job around the kitchen.

Some neat things about CF is that it's never going to rust, or be bothered by saltwater or things left on the blade.

It's so light, I can have it loose in a back pocket, and even jogging I don't even feel the thing. I haven't weighed them yet, but I think they are under 1oz per knife. They almost feel like holding air, yet they are extremely rigid.

No metal means metal detectors won't make you give-up your knife, though these perticular ones are too big for EDC (at least to me).

They look really cool just dry in normal room lighting, but in sunlight when wet, they are hard to even take your eyes off! When I'm slicing up fruits/veggies at the kitchen sink with the sunlight comming in through the window, the knife is so distractingly awesome looking, I've actually cut my fingers from paying more attention to the knife than where I'm cutting.



For people looking to make there own, it's pretty easy. I spent about $400 initially in materials to get the proper carbon fiber epoxy, a small roll of cloth, and some pre-glued carbon fiber strips. I've got enough materials left to make at least 4-5 more knives, so the materials cost is really not too bad, well under $100 a knife for all materials involved if you're going to make a few.


I'm sure the knife making guru's could do the grinding and sanding in under a couple hours, and it would be all perfect. For me, it was the bulk of the time in making each knife.

I estimate I've got about 10hrs of work from start to finish for each knife.


For the people wondering how CF holds an edge, I can tell you it's nothing like good steel.

I can cut soft things with them, like veggies and fruit and trim steaks and things with no issues, and the blade stays sharp.

However, if you start trying to carve wood or hacking through cardboard boxes and things, the blade does lose it's edge very quickly, and hacking at harder things puts tiny little knicks in the blade that a good steel knife would have taken no damage at all from.

It has it's ups and downs as a material. It would certainly make a poor machete, but it does seem to make a fine kitchen knife.



I hope you enjoyed seeing some amateur carbon fiber work pics.

Best Wishes,
-Luke

 

[liveforphysics]

you might be getting a few calls from Jhad extremists looking to do business with you Luke they
would pass through airport security very well just tucked in your sock hahaha

Very nice result mate well done, what programs are you using with your cnc?

KiM

lol, I had thought about that, but if you're well funded and don't care how it looks, I would guess ceramic has the market cornered for Jhad guys.

I'm using Rhino CAD, Cut 2D and Cut 3D CAM, and Mach 3.

And still trying to learn my way around programming the machine effectively! I'm still a totally CNC newby.

 

[AussieJester]

lol, I had thought about that, but if you're well funded and don't care how it looks, I would guess ceramic has the market cornered for Jhad guys.

hehee... maybe the Asian ricer market is better direction to go
the carbon fiber knifes will match all the carbon fiber on their
waaah psssssh ricer cars perhaps
include bluetooth in the handle..."everythings better with Blue tooth" :lol: (you wont get that Luke its a
line from a t.v show The BiG Bang Theory...funny show about geeky nerds..)
At the very least you could incorporate a thumb drive in the handle! Top job anyway
mate...

I'm using Rhino CAD, Cut 2D and Cut 3D CAM, and Mach 3.

I have Rhino and Mach 3 myself, never used either ...really need to finish the cnc machine i started building ;-S

KiM

 

[John in CR]

uber cool Luke. I'm sure by the time you're done most of your car will be carbon fiber except for the ceramic engine.
There's gotta be another 500-600lbs of weight savings possible if you got serious about it, but will it be heavy enough for the tires to stick?

John

 

[liveforphysics]

uber cool Luke. I'm sure by the time you're done most of your car will be carbon fiber except for the ceramic engine.
There's gotta be another 500-600lbs of weight savings possible if you got serious about it, but will it be heavy enough for the tires to stick?

John

Yep, they make CF doors, hood, fenders, and pin-on CF rear hatch replacement for my Civic, and all together you do drop quite a lot of weight, about 300+lbs if I remember right, which would be a HUGE improvement in acceleration for my 1800lbs civic.

The problem is, I gotta keep her looking as completely stock as possible from the outside to keep up the ability to lure suckers into races.

 

[kfong]

Nice job Luke. You need to be careful with carbon fiber dust. It's mentioned a lot in RC groups. I use a vacuum with a hepa filter. Wet sanding will keep the dust levels low as well.

 

[John in CR]

uber cool Luke. I'm sure by the time you're done most of your car will be carbon fiber except for the ceramic engine.
There's gotta be another 500-600lbs of weight savings possible if you got serious about it, but will it be heavy enough for the tires to stick?

John

Yep, they make CF doors, hood, fenders, and pin-on CF rear hatch replacement for my Civic, and all together you do drop quite a lot of weight, about 300+lbs if I remember right, which would be a HUGE improvement in acceleration for my 1800lbs civic.

The problem is, I gotta keep her looking as completely stock as possible from the outside to keep up the ability to lure suckers into races.

Just keep that dull grey paint job, or maybe better let me do the carbon work with the dull grey paint and have it looking like shit but fast. AJ is still staying up nights trying to figure out how to beat Blue in anything more than a 20 meter race. It's worse now that Lyen let my secret weapon out, because AJ knows he has to wait for Collosus to have a chance.

 

[StudEbiker]

Very cool. Nice work. Good skill set to have!

 

[heathyoung]

Pretty Love CF work, looks great.

For practicality, and almost as pretty, damascus steel knives are much nicer I imported some from Japan, (Kikuichi Tsuchime) beautiful knives, take and hold an edge like you would not believe - more work than stainless though.

 

[liveforphysics]

Thank you for the kind words. Funny you should mention damascus.

I'm buying this $224 ceramic sushi knife in a damascus pattern to have water cut into strips to become inserts for my next batch of knives.

 

[spinningmagnets]

Luke, so,...the Damascus steel strips will form the cutting edges of the next batch of knives, and CF will form the rest of the knife blade + handle?

I am fascinated by primitive-tech. I enjoyed reading about how Samurai swords were hand-made using primitive and simple materials and processes, and also how early black-powder rifle barrels were made.

New Englanders often bought barrels, and made the rest of the rifle themselves as a winter-craft when stuck indoors. Eliaphet Remington was sent to a major town to buy several barrels for his father and neighbors...but since he was just a young boy, he was allowed to see them being made. Upon his return, his father de-briefed him on what he saw, and then set up a local barrel-making operation during the winters when he was unable to farm.

 

[liveforphysics]

Luke, so,...the Damascus steel strips will form the cutting edges of the next batch of knives, and CF will form the rest of the knife blade + handle?

I'm using something so much better for an edge than damascus steel, I'm using an extremely modern, extremely high-tech ceramic that happens to have a damascus pattern. I also love damascus steel, but it doesn't meet the criteria goals for me, of passing through metal detectors, never rusting, chemical resistance, no maintenance needed etc etc.

Funny you mention that rifle story, Remington is my actual middle name.

 

[liveforphysics]

Ok, here are some crude pics of my crude testing with laminating metals into the carbon fiber. I'm using Titanium here, but it's only to practice the process of getting the carbon/insert/edge layout laminated to meet my standards for stregnth and visual qualities rather than trying to make knives, so don't go making fun of my stupid triangle blade shapes. They are just test mules to cut apart and pry with and flex and see how things hold up.

You can see I refined the methods on knives 5 and 6 to grab the blade with CF rivot-like shapes. I counter-sunk the holes on both sides, so each little carbon plug has fibers running long-ways down the blade, and through the holes. The result here was a CF/Ti blade that I wad able to fold at about a 45deg off-axis in the vise before the carbon started to crack away from the titanium. You can see the plug shapes in the blade I cut-away as a sacrifice to see how well the plug-insert method filled in with carbon, and I was pleased.

 

[liveforphysics]

BTW- That Ti blade in the last picture I sharpened enough to shave with, and when you mess up and cut yourself with it screwing around, it actually doesn't hurt. You're just surprized to see blood dripping from somewhere and wonder where you got knicked. lol

 

[AussieJester]

I will be bonding CF to metal in the next frame i build Luke
and i also intended to do the holes/plug thang great to
see how well it works, I have done exactly this with fiberglass with good results in the past my head tube, bottom bracket and rear dropouts
will need to be held in such a way. Cheers for the detailed pics mate.

KiM

 

[liveforphysics]

Right on KiM

I learned from my bending tests that just drilling holes was better than no holes, but I wasn't impressed.

Running a bigger bit on each side of each hole to make a counter-sink like chamfer on the holes, so it makes a little CF mushroom/rivot like plug in each hole made a huge improvement. Ripping carbon out of a clean drilled hole might take like 30lbs of tugging, ripping out a mushroom head takes some serious pulling, like hundreds of pounds before it can sheer the edges of the carbon plug and mush the Ti. Yes, the carbon plugs are actually strong enough to roll over the edge inside the titanium before they let go! Kinda a PITA to lay it up so it all conforms to the holes, I poked 12k CF yarn strands in there with the back of a pen, and did my best to kinda weave/tuck things together with the holes before laying more cloth over the outside to make it look pretty. The try where I just laid the cloth over mostly just had the epoxy in the holes, and wasn't as strong as the ones I took the time to ensure good hole fill.

Super super messy work, and takes a lot of time. At first I was kinda pissed the epoxy has a 4hr working time, but after spending 2hrs fiddling around laying cloth and working out bubbles and trying to overlap layers and things for small work like knives, I can see why 4hr work time is critical for doing large parts. But of course I'm sure a pro CF guy would be done in like 10mins. lol

 

[AussieJester]

But of course I'm sure a pro CF guy would be done in like 10mins. lol

4 hours Luke!!! Sheesh hehe.. any fiberglass work i have done over the years sees the resin gumming up after less than 5 minutes with my hot mixes haha.

With the plugs, i would have thought just resin alone would be strong enough for most applications rather than filling them with CF also? I guess it would depend also on what/where the stress was being applied? I shall definitely drill the holes and countersink them after your finds though. For the head tube of my frame i will do anything else you find that ensures a good 'bond' not as concerned if the rear end lays on the road behind me but a front end collapse scares the shit outta me.

KiM

 

[liveforphysics]

but a front end collapse scares the shit outta me.

KiM

As a guy who rides the year range of GSXR with the random frame-neck breaking problem, I totally feel you on that. Everytime I have to set the front down hard from a wheelie, I'm always a little extra 'puckered' for a split second waiting to hear that "SNAP!" sound and find myself flying through the air. lol


When I do fiberglass work, I also mix it hot, and just lay the mat down, poke it with a brush till the bubbles are out and move on. The huge difference with CF is when you're trying to lay it so all the fibers are laying straight and organized in the patterns you want with even spacing and no gaps, and smooth under each layer. With fiberglass, a lump just means you sand it down and it doesn't matter a bit, cause you don't see it. With carbon, if you've got a lump, it means when you sand that surface smooth, you're going to be left with something that looks like a nice mesh of carbon with what looks like a hole in it. lol If you were just doing structual CF though, i think you could go about as fast as fiberglass, but doing it to look pretty is a lot harder than I thought it would be!

 

[AussieJester]

Are you using the same grade epoxy for your layup and laminating coats? I heard lighter weight resin is best used for the layup and then a heavier weight for the final layers for the wank factor bling bling look.

I also came across these-->

These were destined for a backyard made carbon fiber frame, note the holes marked for drilling exactly as you described Luke

KiM

 

[liveforphysics]

I'm using the same epoxy for everything right now. It was like $300 for the epoxy kit I got, it's suposed to be the same stuff they use on helicopter rotors and stuff, and it's high-temp capable, because I originally got it just for making my DIY motor, but then sadly realized that I need to develop some CF skills first before just magically making complex rotor/stator shapes. lol.

Your drop-outs look perfect my friend, and I would expect nothing less. You've got natural engineering skills in you in a big way.

 

[amberwolf]

That pic looked really familiar...I think I remember reading an article about Mark Rehorst's bike project a long while back, and then being sticker-shocked at how much the CF was going to cost when I considered trying something like that myself.


BTW, does "mixing it hot" mean using different proportions in the resin/catalyst mix that cause the resin to cure much faster than usual? It's been...a few years since I did any resin casting, and I never did get around to fiberglass work (though at one time I had some cloth for it to build a better transporter console casing than the PVC sewer pipe/masonite one I first tried, which is still in decent shape even now).

 

[AussieJester]

BTW, does "mixing it hot" mean using different proportions in the resin/catalyst mix that cause the resin to cure much faster than usual?

Yes it does buddy, same term is used when mixing 'hot' batches of bog (bondo/body filler)

In regards to the dropouts i would also have a taper on the ends
to be covered in CF. Extra 'protection' to stop the dropouts pulling out.

KiM

 

[John in CR]

Mixing epoxy in incorrect proportions makes for weaker result. Think of resin and curing molecules that need to match up with each other to form the new hard material. Extra hardener may help the hardener molecules find a resin one quicker, but it leaves unmatched curing molecules at the end like musical chairs, resulting in a weaker material.