DIY: an Ultra Portable Torch Knife




About: Quick and Easy hacks, made for curious people

Hey guys! so its been a while since i've written an ible and i must say, its great to be back! Seems like there's a ton of great instructables recently popping out and i hope this one makes it to your list of favorites ;)

Anyhow, here's a short read about how it was made..

As i was working on my cotton candy machine, here's a little list of problems (aka:opportunities lol) i had encountered back then

Due to the lack of tools at home, i really found it difficult to cut the hard plastic enclosure into a decent circle until i tried heating a retractable cutter blade with a lighter and to my not-so surprise, it worked quite well! but then an idea sparked from that simple combination of tools, what if i built a heating system that could be mounted on a cutter? after a handful of developments andinstantly cauterized cuts on my thigh, i finally realized an x-acto™ knife would do the perfect job! Both aesthetically and functionally.

To me, this is one of the most important tools i've had lying in my workspace so far and i can't wait for you guys to make one of your own! i hope you enjoy this instructable and also find this tool's worth in your next creative ventures, so let's get started!

So, why an x-acto™ knife you ask???

I decided this would be the perfect knife to use due to it's sleek and minimalist design but ultimately because of its body's aluminum construction. As we all know, aluminum is probably one of the most well known heat conductors and a really light metal so it is given that this tool is slightly gonna heat up but then since it's body is aluminum, the heat dissipates in no time therefore cooling is never really a problem.

Hey! what's the knife's main purpose anyway?

Well i designed this knife mainly to cut plastics with precision and at the same time with ease, and later discovered that i can sculpt styrofoam for making lost foam casting and what not, cutting plastic rope without fraying those delicate strands, and also cutting styrofoam without it turning into snow and leaving a huge mess and really bad squeaky sounds.

Here's a late foreword: I kinda had to recycle old pictures cause i ran out of funds to replicate another torch, sorry about that :(

Oh and i recently entered my instructable in these contests: Tools And Guerilla Design! Just take your time and click vote to support this instructable :))

(and if you still didn't know, i really do appreciate your help, thanks!)

UPDATE 3/8/2015 (asia time)

Hi guys! uploaded 2 new demo videos and a handful of pictures, go check it out!

Step 1: Parts, Assemble!

Here's a quick list of the stuff you need

Note: I added links to some of the stuff you might need


  • Screwdriver
  • Cutter
  • epoxy
  • Super glue or any cyanoacrylate based adhesive


Step 2: Disassemble to Assemble (heating System)

in this step you're gonna need:

  • A long nosed lighter
  • A Jet flame / torch lighter
  • Screwdriver
  • Superglue
  • an assortment of wires

So you'll need to open both lighters and once they're both gutted out, see Pic 2 for the parts you'll be needing....if the part wasn't mentioned, you will not be needing it so just put it in your scrap parts for another project.

Okay, did you check out the picture? Good. so glue the torch to its housing then look at image 5, see that hole? put the main ignition wire (the black wire connected to the side of the piezoelectric igniter) through that and bend it just like in image 7.

now you will want to glue the ignition wire (the red wire connected to the metal base of the piezoelectric igniter, see image 9) exactly like in image 8 to the brass part of the torch, DON'T block the hole above it!

Once that's all done, give your igniter a squeeze and see if there is a spark gap between the torch and the wire. If so, Congratulations! Connect your silicone fuel hose to the torch to test and fire it up!

Step 3: Callibration of the Torch-to-cutter Blade and Epoxy

So i guess by now, you probably realized how versatile that little torch is eh? :D

but we're not just done yet, in this step we're gonna need

  • Epoxy
  • A cutter
  • X-acto™ knife
  • Wires
  • Gutted out lighter parts
  • Piezoelectric igniter
  • A protractor (optional)

So to start off, grab your protractor and try to point the torch to get an angle of at least 20° or slightly higher pointing to the blade, then you're gonna want to cut off a portion of epoxy and mix/knead it thoroughly then temporarily fix the torch to the X-acto's grip just so you won't have trouble when adding the rest of the epoxy. (see image 1)

Oh yeah, take note of this: Remember that hole in the previous step i told you not to cover? Well, you still shouldn't. first off, grab some scrap wire then thread it through the torch's hole to avoid epoxy getting in ;) (see images 2-4)

Once that's all sturdy and dry, fill in the rest with epoxy and try to be neat. no worries, you can use the cutter to easily take out the extra epoxy with ease!

Once you're all good, and the heating system's epoxy is hardened, we'll now be making the cutter's ignition!

Knead a bit of the epoxy thoroughly and then you're gonna want to grab some tape to cover the igniter's holes to avoid the epoxy from getting in and clogging the mechanisms (srsly tho you really gotta do this) (see images 5-7)

Oh! and remember those wires we left out sticking off the torch earlier? we'll finally be connecting it to the igniter! so connect the red wire to the igniter's metal base and the black wire to the igniter's wire. (see images 8-9)

After connecting, just coat the ignition with epoxy and you're done! (see images 10-13)

Step 4: Fuel Injection System

Now, as you can probably tell by now, we're basically almost done!

so in this step we'll be neding:

  • The gutted out fuel tank
  • The long fuel hose
  • Superglue/epoxy

Secure the fuel tank with a rubber band to the lower handle of the X-acto knife then glaze a generous amount of superglue in between the two. (see image 1)

Then connect your fuel hose to the main tank to the torch, you may glue it so the hose wouldn't come off too easily (see images 2-5)

and that's about it!

Step 5: A Couple of Videos and Some Good Reads

So here are the videos!

(btw just scroll through the images for the video)


So yeah, i guess by now you figured out that i used this knife in the arduino enclosure instructable i posted a couple of months ago, and my cuts were pretty bad back then although, i sorta mastered my tool and it really gets things done around here

So i'm actually designing a proper enclosure on sketchup for 3d printing so that the cutter wouldn't look too guerilla and to give it a little bit more aesthetics. Wouldn't be able to show it for now, its just that my final exam is coming in a few days so yeah... ya feel?

Notice on the foam cutting test video, the last cut had a nice crunchy sound to it, that was becuase it was sorta losing some heat due to it being spent on the previous soundless cuts

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31 Discussions


4 years ago on Introduction

I just got a new soldering iron and really want to test it out, so I was wondering, could I use that instead of glue or such for some parts of this project?

3 replies
oky jimstephenmack

Reply 3 years ago

yes you can use a soldering iron for this. I have what is called a soldering pen. it has a screw to hold the soldering tip in place. Get some of those small breakoff blades for a utility knife and you will see the end one has a hole in if. just fasten the blade on the pen with the screw and go to work.....break off all the other blades to avoid having too much length and possibly cutting or burning yourself.


Reply 4 years ago

Not really. You could of course try to solder the wires from the igniter, but that's the only thing you could solder on.


3 years ago

Super cool project, thanks for posting it.


4 years ago on Introduction

I would cover the tube somehow. I would be worried that it might get caught on something and get pulled out.

2 replies

4 years ago on Introduction

would this work with an x-acto where the "shaft" is covered in the rubber grippy stuff? does the whole thing get too hot? or no, just the blade?

looks like an awesome project... i picked up all the parts i need and just have this one question about the xacto knife itself before i get started.


3 replies

Reply 4 years ago on Introduction

Depends on the rubber, but most likely that's not the best idea. Saying this mainly because even a solder iron gets pretty warm on the plastic handle far from the tip after enough soldering and this would be only metal.


Reply 4 years ago

hi, justradar! sorry for the late reply. well what you should consider is that if the part where the blade is being held is made of metal, you're good :) oh! if you could send me a picture It would help out more


4 years ago on Step 2

Nice idea! i might just make one of these


Reply 4 years ago

oh, sorry about the glass part, no it couldn't cut glass hahaha


Reply 4 years ago on Introduction

YES it definitely can! although you'll need to do a little bit of sanding, nothing beats the classic scratch method


4 years ago on Introduction

Interesting ible. I use a Dremel VersaTip butane torch, which comes with an X-acto type knife tip (among several others that are very useful).