Introduction: Blade Firing K'nex Knife

Picture of Blade Firing K'nex Knife

This instructable is on how to make a knife which can fire its blade. Useful when you are down to a knife when your opponent still has a gun, you can lull them into a false sense of security muahahaha! It can also fire small pellets.

I am not going to say 'it is my first instructable so be nice' because i hate it when people say that, so feel free to say so if it is rubbish. However, i do not want people saying bad things about k'nex in general.



Step 1: Pieces Needed:

Picture of Pieces Needed:

8 yellow 5-way connectors
4 red 3-way connectors
1 ball socket connector
1 light grey two-way connector
2 hand connectors
8 white rods
9 green rods
1 yellow rod
2 bendy orange/red rods the length of yellow rods
2 elastic bands

all knex colours are in the metallic colours.

pic 2: you will also need these three pieces.

Step 2: Make Frame

Picture of Make Frame

Make both of these identical pieces.

Step 3: Make Trigger, Ram, Ram Aligner and Side Support

Picture of Make Trigger, Ram, Ram Aligner and Side Support

pic 1: trigger

pic 2: ram

pic 3: ram aligner

pic 4: side support

Step 4: Make Blade and Pellet

Picture of Make Blade and Pellet

pic 1: blade

pic 2: pellet

Step 5: Assemble the Knife

Picture of Assemble the Knife

pic 1: take the frame pieces

pic 2: add the side support with a white rod

pic 3: add the other side of the frame

pic 4: insert a white rod through the hole indicated

pic 5: add frame aligner

pic 6: snap white rod on where indicated

pic 7: add trigger

pic 8: insert ram

pic 9:

Step 6: Adding Elastics

Picture of Adding Elastics

pic 1: where the ram elastic goes

pic 2: where the trigger elastic goes

Step 7: Loading and Firing

Picture of Loading and Firing

pic 1: the blade has to be this way up. push it in until the trigger makes a small clicking noise.

pic 2: the blade is now loaded

pic 3: the pellet must be this way up also

pic 4: the pellet is loaded

to fire press the trigger forwards

Step 8: Mods

Picture of Mods

to make it more powerful, you can lengthen the frame and lengthen and strengthen the ram.


the_boss_builder (author)2013-05-20

Give it a real blade and "BOOM" it's a completely illegal weapon that can get you arrested, potentially the first ever legitimate knex weapon. background info, any projectile weapon not classified as a gun or A.O.W. (any other weapon), both of which use gunpowder is completely illegal to own or fire.

NathanStrickland (author)2012-11-02

dude the knifegun is seriously EPIC! as for the super knex rifle thatguy was talking complete BS about, he is full of BS cuz my dads an engineer and he said that it would be impossible for a knex gun to do that without being reduced to rubble. any way im going to try and improve on this knife cuz i have too much time and nothin to do.

XxsonicxX (author)2011-08-07

epic but i can't get fotos on

XxsonicxX (author)2011-08-07

almost for got i will post photo soon

XxsonicxX (author)2011-08-07

I just made it omg!

At first i could not fin the bendy pieces
Then i did not have the ball joint thing, but i did make a sub for it a pulple/grey one way connector.

urtlesquirt (author)2011-05-23

Nice dude.I love blade warfare opposed to guns. they are just so much beter for killing zombies :)!

verektemongul (author)2011-04-08

this thing is freakin awsome!!!!!!!!!!!!!

OneTastyBurger (author)2011-04-01

hey guys try my knife

skyfaller (author)2011-02-13

I love this! I made 2 and made them into one. Knife shotgun anybody?

explosiveknex (author)2010-12-19

awesome! just like in black ops. 5 stars!

knexguy (author)explosiveknex2010-12-23

Thanks, when I posted this, I saw 3 years into the future and realised this weapon would become popular when Black Ops came out :D

skyfaller (author)knexguy2011-02-11

That just made my day.

flyerminer (author)2010-11-22

it's really called a ballistic knife.

knexguy (author)flyerminer2010-11-29

Hahaha, this made me laugh. I just love it when people play CoD and then think they know all the weaponary terminology on the planet.

safety dance (author)2008-04-02

LOL, this deserves the list more than mine 455#013!! xD

knexguy (author)safety dance2008-04-03

How? It's a completely new concept AND mechanism!

safety dance (author)knexguy2008-06-04

Becuz, it sux azz. LOL

knexguy (author)safety dance2008-06-05

Learn to spell. And because I found these amusing pictures, I shall use them.

Jahoovi (author)knexguy2008-06-25


knexguy (author)Jahoovi2008-06-26


mankros_dakren (author)knexguy2010-05-11

 SLASHDOTTED!/. (Not really, though; still a cool i'ble


How are people still finding this instructable? Does it go to Zeitgiest every time someone posts a comment here?

TwistedParadox (author)knexguy2009-04-08

isn't Zeitgiest some annoying conspiracy thing?

knexguy (author)TwistedParadox2009-04-09

Lol, it shows what people are looking at and commenting on at the time you look at it. Kind of like the 'recent' column for instructables.



bannana inventor (author)knexguy2008-07-02

What NOOB mean. I kind of have an idea though...

knexguy (author)bannana inventor2008-07-02

1: Noob means newbie, someone new at something. It is a term generally used by people on the internet. 2: WHAT'S THE IDEA?

bannana inventor (author)knexguy2008-07-02

Thanks. :D

knex_mepalm (author)2009-05-10

it's ok but still worthless against the knex rifle131029 which means to the power of 131029 normal rifles. I shot a bb through 2 bricks! I'm going to post it soon

knexguy (author)knex_mepalm2009-05-11

Erm... get off my Instructable spammer. Also, that is impossible. It will probably be in line with the other countless useless creations on this site... But go ahead, prove me wrong. I hope you do.

knex_mepalm (author)knexguy2009-05-17

It uses an engine though anyway I'm sorry I spammed I was reckless then but now I'm working on a slightly stronger one with better grip cause the recoil hurts a lot. it's not useless it's "different"

knexguy (author)knex_mepalm2009-05-17

Engine? And recoil is pretty much impossible for a K'nex gun.

knex_mepalm (author)knexguy2009-05-19

" PRETTY MUCH IMPOSSIBLE." Beacause of the extreme force hitting the bullet there will be energy waves shifting the environment making it have recoil. *UPDATE* I found out it's not recoil, its just the rod flying back and hitting on my arm when I forgot to install the safety. Sorry 'bout that. AND PKTRAUCER, I will post video but im testing it 100 times to make sure that It can shoot like that

 Um, I'm 100% sure that the power of 131,029 rifles is enough to reduce ANY K'Nex creation to a pile of broken plastic, but please, by all means, continue to tell us about it. We need to know EXACT details for when K'Nex become illegal for children and felons to own because of their potential as a firearm.

 The rifle bit has 45 rubberbands attached to a rotating motor which spins the bullet at incredibly high speeds. The fornt of the knex gun is roughly 11 pieces thick and sort of airproof, then another bit at the back is 7 pieces thick and still air proof is pimping 150 fps of air through the gun, at the end is the bullet. The bullet is 14 melted bbs together and then with a wire sticking  into it making it constantly molten, when shot the bb, goes whizzing through the air at 450 kph and at 950 degrees C and wham into the brick. The end. The front of the gun breaks off every time is test it.

 #1:fps measures SPEED, not air pressure.
#2:If the bb's were "constantly molten", they would flow(because molten metal, being a LIQUID flows.)through the gun, melting it to unusable plastic chunks.
If you still stand by your words, it  won't bother me.

BlondGuy101 (author)knex_mepalm2009-07-27

I greatly look forward to that

PKTraceur (author)knex_mepalm2009-05-18

Umm...i'm not totally sure, but that's physically impossible. Knex is plastic. AR-15 is metal, and shoots lead at approximately 2800 fps. An AR-15 can barely if not at all, go through two bricks at 50'. Please, don't spam instructables with things like this. Post a video to show me, prove me wrong, that your knex rifle 131029 can go through two bricks. -PKT

leeboy09 (author)2009-05-29

yes it was ace

m1n1j1mmy (author)2009-02-08

ive seen better... but its still pretty damn cool a knex knife that shoots its own blade :-D

knexguy (author)m1n1j1mmy2009-04-09

And how many of the 'better' ones were posted before this?

knexguy (author)m1n1j1mmy2009-02-09

Well, this is 1 and a half years old.

TwistedParadox (author)2009-04-08

I was watching the Punisher a few days ago and I was trying to find a fblade which could be fired. w00t for this!

knexguy (author)TwistedParadox2009-04-09


leeboy09 (author)2008-12-21

yeah its realy AWSOME!!! your a knex master

knexguy (author)leeboy092008-12-21


leeboy09 (author)2008-12-20

i think this is awsome your real good ive never built an instructable lol

knexguy (author)leeboy092008-12-21

Thanks, have you built it?

About This Instructable




Bio: short, blonde Some of my favourite quotes: DJ Radio: and I wonder why the hell we have different languages, and not just one main language ... More »
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