Introduction: How to Forge a Throwing Knife

Picture of How to Forge a Throwing Knife

I didn't win the race to post the first forged knife on the site, so i'll have to settle for second best. rocketscientist2105 posted "i want to try making a throwing knife (bascically a rod with the end flatend, no sharpening nesscicary). Can I use rebar instead of a car spring?" on jtobako's knife forging instructable, and i thought that i could post an instructable on that.
After repeated threats to my physical wellbeing and a bit of wheedling by rocketscientist2105, i was finally persuaded to put a link to his orangeboard.

Step 1: Select the Steel

Picture of Select the Steel

I'm posting this Instructable assuming that you already have a hot enough fire, an anvil of sorts and an appropriate hammer, as well as all the other stuff. The first step is to find the steel you're using to make the knife with. My suggestion to you is: Use a tool.
Tools are made from hard steel, right? They usually are.
If the tool you're using has to put up with a lot of bending and twisting and hammering and general abuse, it'll probably be a meduim carbon steel, or a spring steel. Either of these is fine, in fact you could just use a bit of a car spring like jtobako did, that'll do the job perfectly, because throwing knives need to be flexible. If the tool you're using has to be hard and wear-resistant, like a file or a drill bit (I don't recommend using drill bits.) then it'll most likely be high carbon steel. I used a file. The first thing we need to think about when forging files is that they have teeth. Forge them with the teeth still on and you'll trap scale in the gaps, then fold the teeth over. it'll be terrible. Grind the teeth off the file. it helps if you anneal the steel before you do this. To anneal steel, get a good fire going and chuck the steel in. Let the whole piece get to a dull red heat and then let the fire die off slowly. If you anneal the file, you won't wear away your grinding wheel too quickly.

Step 2: Start Forging...or Not.

Picture of Start Forging...or Not.

I went for a Japenese-ninja-kunai-naruto-ish inspired thing here. I don't watch Naruto, but a lot of my freinds do, so i made this in the hopes that they'll buy some...;)
I looked up the naruto kunai on the interweb and its a lot different to the normal Japanese kunai (intended as a tool, like a trowel, or a wrecking bar, not a weapon) it LOOKS alright, with a triangular dagger blade and a ring on the handle. I couldn't be bothered to shape the steel into the triangly-shape, and i'm not going to learn to forge weld, just to get the loop on the end closed, so i'll add my own little features that'll make it much easier for me to forge it, but not detract from its functionality.
The blade will be a knife blade; only one side sharp, and the loop will be open-ish. In the next step, i'll show you how i made the loop.

Step 3: Make the Loop

Picture of Make the Loop

To make the loop on the end of the knife, i bent the steel. A lot. I know it's fairly obvious that you'd have to bend the steel to get bendy steel but i just needed to say that. Start by drawing out about 4 inches of the file. To draw out steel, heat the bit you want to work to forging heat and hit it on one side, then turn it through 90 degrees and hit it some more on the other side. you reduce the width and depth but increase the volume. Draw it out till its about 3/4 its original thickness. Once you've drawn it out, you'll need to bend it through 90 degrees, so it looks like the first picture.
For the next step of the bendening, you'll need to make a quwstion-markish sort of shape, by bending it around again.
Now comes the tricky part, you'll need to get inside the flat bit and bend that over too. My best advise is Be Creative.
Finally in this step, finish the bendification by pushing the end of the steel over to meet the main part of the bar. After that, I hot-cut off the rest of the file, that I hadn't ground so it was smaller and easier to work with. Now its about 6 inches long with a loop on the end.

Step 4: Forge the Blade

Picture of Forge the Blade

You now need to forge the blade of the knife. Start by making it a bit more Square-ish. Just heat it to forging heat and hit it till its more a rectangle than a cirle in its cross section (i started with a round file) Once you've done that, start forging the tip. Get the steel in your pliers or tongs and hit the hot end till it gets compressed and looks sort of like the tip of a knife. This is basically a variant on the drawing-out i mentioned in the last step. We'll be grinding it later, so don't worry if the tip's still thich and heavy, all you want to do in this step is to get it started.
Forge the blade by heating it up, holding it at an angle to the anvil and hitting it to create a blade shape. jtobako's got a much better instructable on making the bevel. Once the shape of the knife is made, let it cool slowly, and i mean really slowly. Hang it in the air if you can, or put it on some sand. If you found the meaning in my appalling description and put it into practice, you should have something that looks like this.

Step 5: Grind It to Shape

Picture of Grind It to Shape

There will awlaws be a need to grind a forged object. Lets face it, forging's hardly the most precise of procedures, anyway.
If you want to do it by hand, use a vice and a file. Have fun in your toils, I wish you well! Personally, I believe that tools are made to be used. That's why i'm using my bench grinder to take away all the excess steel. This beast bites deep and does it quickly. One moment's lack of attention could have you looking on the floor for your fingers or, even worse, could completely mess up your knife! porceed with caution. Once it's been ground to shape, you should set about removing the grind lines. THIS is where I recommend a file, and a fine one at that. Again, proceed carefully. After the file, I moved on to a coarse waterstone.
I know for a fact that the best way to proceed is to get most, if not all of the necessary shaping and grinding out of the way before heat-treating the steel, I mean, why make extra work for yourself?

Step 6: Heat-treat the Blade

Heat-treating steel's a two step operation. First, you heat it up, and cool it quickly. Second, you heat it up slowly, as slowly as possible, and watch for the colours. you're going from hard and brittle to soft and springy. Yellow is the brittle one, Blue is the soft one. (a blue temper is still quite hard, in good steels)
All hardened blades need tempering, but some more than others. Throwing knives need to be very tough, because they smash into things with great force. If it cracks, it's an embarassment to the person using it, and to the person who made it.
So, warm up the steel with a blowtorch, or in your forge, it doesn't matter, as long as it gets hot enough. There is a point at which the steel's internal structure changes from the soft crystals called Ferrite into Austensite. This is the point at which the steel is Quenched. (luckily, as the steel changes its crystal form, it stops being magnetic, that makes things a lot easier, doesn't it?) Quenching the steel cools it rapidly and changes the Austensite into Martensite. By quenching the steel, we are imparting tremendous stress to its crystals, this is what makes hardened steel hard. But it's brittle, too, so what are we to do?
Temper it. Change some of the Martensite into Troosite.
To temper the hardened steel, you need to warm it up again, but not as much this time. I suggest that you either do it slowly with a blowtorch, or, if you're using a coal forge, that you heat up a big lump of steel ot a dull red heat and let the knife draw heat out of the lump and into itself. You're looking for an all-over blue temper on this one. Don't let it get too hot, otherwise that lovely blue colour will lose its brilliance and the knife will lose its toughness. A quick note: Steels with more carbon in them need tempering slightly more for the same effect. Experience is the only real teacher here.

Step 7: Polish and Test the Blade

Picture of Polish and Test the Blade

There's no eral need to polish the blade, it just makes it a bit shinier. If you're happy with the tempering colours, leave it, however, you DO need to test the blade. To test for cracks and toughness, clamp about 1/4 of the blade in a vise (pad the jaws of the vise with leather or cloth, or wood or something) and lean your weight on it. If it cracks, ot wasn't a good knife anyway and its a good thing you're rid of it. Go make another one. If it bends by a significant amount and flexes back to its original shape, you've succeeded. You now have a functional throwing knife, made to your own tastes and preferences.
But there's one more thing. You have a knife, but its time to have some fun. Got a shed? some cardboard boxes? irritating neighbours?
I think you know what to do.
Thanks for getting to the end of this, don't hesitate to ask me any questions. I know I could have been clearer on most of the points I made.


jackman134 (author)2016-04-14

Nice work and thanks for sharing. I am definitely going to make this.

shmyt (author)2010-07-12

It would have been better to have it double edged IMHO, it looks awesomer that way.

EaglesSoar09 (author)2010-07-09

Nice sound effects on the first pic.

Landon Sullivan (author)2010-07-07

This seems like I could do this relatively easily with an eye bolt. Could this be done or is the metal wrong for the task?

bananna39 (author)2010-04-20

Nice, but I noticed this in step 7.

"There's no eral need to polish the blade..."

icecoldcelt (author)2010-03-01

It may be late to comment, but I find it to be much easier to start from the other end of the loop, making it curl like a finger and then making the 90 degree bend with the loop through the horn.

Proffessor Luke (author)2009-10-01

Have a look on Sk8master's 'How to throw a knife'. It isnt that bad.

Notbob (author)2008-03-22

This might sound stupid but.... how do you properly throw a throwing knife?

I've always found that throwing a knife is either all your own or by the book. The "by the book" way is really anal and you apparently have to throw it perfectly vertical (over your head) which really hurts my power. But the base ball way is kind of over the shoulder and is more horizontal. That is where my strength is. But thats just me. Also try to feel the throw. When you first get your hands on a knife, you want to get a feel for it. By this I mean you want to know how its going to spin before you throw it. To do this find your main hand position and stick with it. Say you hold it by the blade and you want to get a half spin and thus a hit. You have to experiment with different distances and hand positions. When you find a good distance, keep throwing from there. You will get a memory of the distance of a half throw. Mine is about 3-4 feet. But that depends on the size of the knife. From then on you can judge how many half spins it takes to make a full 180-360-450etc spin and increase the distance between you and the target. You can keep going from there and you're only limited to how far you can throw. Good luck.

TheDeviant13 (author)Notbob2009-04-18

a look at this instructable might help

Vendigroth (author)Notbob2008-03-22

It's certainly not a stupid question, but i don't know for sure.
I stuck it into the shed door from 10 feet by holding it at the balance point thensort of...throwing it....
Practice is key, eh?

Notbob (author)Vendigroth2008-03-23

thanks. as my parents always say: practice, practice, practice!

die_dunkelheit (author)Notbob2008-03-24

I think I might make my first Istructable on how to throw a knife... Do you think that the website admins would have a problem with it?

Do it, there's lots more dangerous stuff here.

sona (author)Vendigroth2008-08-27

Examples are: firewire, fire breathing, most of tetranitrates instructables, potato guns, this I know because on certain computers I use instructables is blocked for being: terrorist/millitant/extremist. Wow insane lack of punctuation. But i've never considered myself sane by any means. So... yeah there's way worse stuff out there.

blugyblug (author)sona2008-12-28

Waoh! Terrorist/millitant/extremist Aww man thats hilarious. This 9/11 world is very paranoid. But sometimes they just go over the top.

sona (author)blugyblug2009-01-07

=( I haven't done an instuctable yet. Might do one on game maker...

yup paranoia runs deep in the human genome.

...Never considered myself totally human either.

Notbob (author)die_dunkelheit2008-03-24

Probably not seeing as the group "most to very dangerous" has more dangerous things then that. Although i wouldn't be able to give you a definit answer seeing as i'm not an admin.

die_dunkelheit (author)Notbob2008-03-24

Well, I made the decision about 2 seconds after posting that question to go ahead and make the Instructable. It's about 90% done.

My Instructable is UP!! CHECK IT OUT!! titled "Knife Throwing"

blugyblug (author)Notbob2008-12-28

Search, theres an ible I read somewhere. Its mainly common sense though. (See how far it travels when the knife does 1 full revolution)

IkilledKenny (author)Notbob2008-12-11

I have been throwing knives for years and there is one thing that is most important. When you start, get about 10 or 20 IDENTICAL throwing knives (or as many as you can afford, they are cheap.) Everyone has there own way of throwing, and you hold the knife in a different position for almost every distance, after awhile you will find the right grip for the right distance, it almost just happens by itself. Make sure you don't flick the knife like in the movies, let it slide from your hand in a smooth fluid motion. You should end up with your fingers extended like you are pointing at the target. If you have any other questions, just lemme know.

Pumpkin$ (author)Notbob2008-11-27

don't worry about being judged XD I find that when throwing knifes like this you want to find the center of gravity (were it balances evenly on your finger) and place the back end of it in the little line in your palm that's between the middle of your palm,the bottom of your hand, and the tendons that pull your thumb inwards and then holding however you would like to throw it in a stiff manner like a frisby stopping mid throw and releasing it

Masteroffencing (author)Notbob2008-11-07

if u search throwing knife on here it pulls up an ible about it but i learned when i was like 7

OldOwlIronworks (author)Notbob2008-09-06

i found that six normal strides from your target and releasing it when strait out. an multiple of six will work as well...

robotmastern (author)2009-07-21

id be carefull with the axe in the vice as i broke mine that way

cava002 (author)2009-05-06

hahahahahaha LOL irritaiting neighbors

josh1324 (author)2009-03-29

Great instructable! I never thought of using a sledge hammer as an anvil, great idea!

thoraxe (author)2008-01-18

make sure you dont hold the blade too long on the grinder or it will heat the steel and damage it. Make sure to dip it in water

Austringer (author)thoraxe2008-03-30

Since he's heat treating it later, it's still soft and overheating it here won't damage the final product. Over heating the final product will send you back to step six. Most steels when normalized (allowed to air cool) are reasonably soft. Some need to be annealed, which is usually done by burying the hot metal (dull red maybe) in sand or vermiculite to cool slowly enough to stay soft. A few will air harden so that once made hot you pretty much have to have a computer controlled oven to anneal them and one you're done forging them, they're hard. If you are working with the right alloy and have an electric oven you can skip the watching the colors run part of the tempering process by putting your hardened piece of steel in the electric oven, setting it to self clean, and making yourself a sandwich.

stoobers (author)Austringer2008-10-28

I think thoraxe is right. I was taught by a machinist that when grinding a carbon or high speed steel, you can't reclaim the overheated areas. You had to grind them clean off. Some types are hardening are a one way trip! Once it turns purple, its gone for good.

thoraxe (author)Austringer2008-03-30

oh, i didnt read dat part

valkiraun (author)2008-10-05

Excellent instructable. However, i am in the situation where I do not have a forging workshop (anvil and immense heat) so what should i do then?

Vendigroth (author)valkiraun2008-10-05

Take a bar of softened steel, some saws, files and sandpaper and work from there. It'll take a shile, though.

finfan7 (author)2007-08-09

I am definitely going to make one of these but as i was reading this i realized something that made me laugh. You tested it by just chucking it at your shutters. heheheh

Vendigroth (author)finfan72007-08-09

there's no point mking something if you can't test it on the shed. Smoeday, i'll get the bugger to collapse!

I beat you to it, three times over now... we had a great shed, I built a really heavy duty roof for it so i could sit on it, too many people one night and the walls decided to give way... I then used the roof which cam off undamaged on the nest shed, which gave way to a slight miscalculation in explosive power. The first one was when I was ten and my mum asked me to start the car (big old volvo) and i forgot to put it into neutral. that said putting a two tonne car through a shed is fun. Now im building another roof for the bin bit (wierd houses have them...) it's good strong fence all round so another sitting roof! what will destroy is this time? a rocket bicycle?

how about an anarchist?

sona (author)killerjackalope2008-08-27

I don't know about destroying sheds (aside from my suggestion to vendigroth.) but you can always make id destroy other things by running an electic current through it. only works on sheds made from conductive metal =( though that should keep the squirrels out.

Try a homemade firework or just basic gun or flash powder. For the more mechanically minded, an excavator should do the trick. For those without access to explosives- Propane tank+window+flaming arrow=BOOM

not inventive enough, though I have crushed a few cars with a forklift and used the same one to win the forklift speed challenge, which involved me having the engine bay open to reach into the top of the gearbox and shift in to the gear I labelled as 'full kilter' and a bit of easy start just coming up on the camera spot, 31mph is my personal best the original record stood at 24mph... On revving down a bit after getting the record part of the exhaust detonated... But anyway back to point I think it's gotta be more insane than that, I did put the front wheel of my old bike through one of the fence panels on a wet day by accident, you actually reminded me I have to get a move on with that roof...

sona (author)Vendigroth2008-08-27

Try doing a manmade sinkhole. I believe this can be accomplished by pumping water into the ground, though i'm not sure of the specifics.

I test my stuff on the family cats.... Man they run fast.

finfan7 (author)Vendigroth2007-08-13

I got some stuff and am working on building a miniforge. I have an anvil set up in my back yard but until now I have been using the scorching Arizona desert sun to heat my metal bits. But once I finish the forge and tongs I will make this knife.

Vendigroth (author)finfan72007-08-14

glad you like it! I'll have some new stuff as soon as i can get a forge that can delever a decent heat, and an anvil that's not going to give me carpal tunnel syndrome.

packman (author)2008-06-04

hey this thing looks cool but it is leathal and iam shur there not legal in the united states but its still cool

Vendigroth (author)packman2008-06-04

It MIGHT be lethal, but as far as i know, its new owner uses it to open his beer.

packman (author)Vendigroth2008-06-05

hey just as long as the cops dont see it then he should be fine the only reason i siad what i said is because black ops men use the same thing i have gone to where they train and it is no walk in the park ps my dad was a trainer there thats how i got in

jakezcop (author)packman2008-06-10

since when are knives elegal in the u.s.? i own tones of knives (hamade and not)

chuckr44 (author)jakezcop2008-09-04

It is legal to own knives in the US. It is not legal to carry a knife with a blade over 4 inches in Michigan. This limit varies by jurisdiction.

About This Instructable




Bio: I shouldn't have to tell you that using a dagger to undo this little, fiddly screw's a bad idea. AAAAARGH! big project ^^ so ... More »
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