Introduction: DIY Thermic Lance Kit - Cut Steel With Burning Iron

I came up with this project in an effort to replicate industrially made thermic lances in a small, mobile form factor. In this way I can throw them easily in the toolbox of my truck for use on road trips or on the trail in case of emergency. Their use commercially is usually for demolition purposes as they have the ability to cut through incredible thicknesses of steel. Both because of the extreme heat they produce as well as their ability to oxidize and burn whatever material they are cutting, in addition to the simple melting action that would be provided by a torch.

The video I have embedded above will provide the clearest demonstration of the lance kit I have created, but I will also include some written descriptions in the following pages.

Step 1: Principles of Combustion

Picture of Principles of Combustion

The function by which a thermic lance works is the rapid oxidation of iron into Fe2O3, iron oxide (rust). The same reaction occurs when steel wool is ignited and spun on a wire, creating a large amount of sparks as molten iron is thrown into the air. In that case the steel is able to oxidize quickly enough to sustain a combustion reaction because it has been very finely divided into strands, creating a large amount of surface area to react with atmospheric air. A thermic lance has far less surface area so it requires a much higher concentration of oxygen to sustain combustion.

Step 2: Materials

Picture of Materials

Industrial thermic lances would usually use the oxygen supply from large cylinders made for oxy-acetylene torches, but the purpose of my kit is to be portable. For that reason I have chosen to use disposable oxygen bottles. These bottles are equipped with a reverse thread, made so to prevent someone from threading them into a torch or fitting not made for use with oxygen. To attach to these cylinders I purchased a fitting made to adapt them to a 1/4" hose output. These usually are used for certain aspects of homebrewing, so they may be available locally at a well equipped brewing supply store. I purchased mine on ebay.

A length of 1/4" vinyl tube is also necessary, and can be connected directly to the hose barb on the tank fitting.

The lances themselves are simply a 5/16" diameter automotive brake line, approximately 2-3 feet in length. I purchase them in longer lengths then necessary, then cut them in half to get two lances for a better value.

Step 3: Construction

Picture of Construction

Whether or not the brake line used for this project is purchased as a double length and cut in half, at least one end will need to be cut off to remove the flare. This will allow the line to fit snugly inside the 1/4" vinyl tube on the oxygen fitting.

Igniting a steel brake line is a difficult task, even with the assistance of pure oxygen. A commercially made thermic lance would typically require a secondary oxy-acetylene torch in order to produce a flame hot enough to get the reaction started. For my lances I realized that fine 0000 grade steel wool with the assistance of a pure oxygen supply would burn more than hot enough to get the job done. A small portion of wool is inserted into the open end of the lance to prepare it for use.

Step 4: Ignition and Use

Picture of Ignition and Use

The steel wool that has been inserted into the end of the line can be easily ignited with the standard flame from a lighter. If the oxygen supply is slowly turned on while the wool burns it quickly increases in temperature, enough so that the end of the brake line is able to catch fire itself. At this point so long as the oxygen is flowing the lance will burn from the end, allowing it to cut through whatever material it is directed against.

I have found this design to work very well. The primary concern is for safety, as using a vinyl tube to carry oxygen poses a very real risk of the tube catching fire, whether by a leak or a wayward droplet of molten iron. For that reason it is important to wear full safety gear, including welding gloves and mask. An oxygen rich flame has the ability to burn through any organic material quite quickly, even leather, so that can pose other risks. No one should attempt working with thermic lances of any kind without previous experience and training using oxygen supplied cutting methods.


Old World Projects (author)2017-11-04

Are there any known alternatives to breakline that we can use? Copper pipe?

joshiii92 (author)2015-10-11

I like your idea. My Dad has done a lot of welding & cutting in his time, he used to tell me that if someone does a lot of underwater cutting it can make your bones turn like chalk - not really sure what he meant. You can buy arc air gouging carbons (copper coated carbon rods) quite cheap. I think the gouging torch is the same, it uses oxygen and a DC welder. I remember seeing it being done once, its super loud and really, really messy - molten metal spraying everywhere.

Anyway, awesome idea.. :D

Volkivich (author)joshiii922017-01-29

I think your father may have been referring to a condition which can affect any diver who spends considerable time under pressure. The condition is called osteonecrosis which is similar to osteoporosis but is where the bones actually decay & die. Bone rot is a slang name some divers use. It has nothing to do with welding underwater, but is a result of prolonged exposure to high pressures while underwater. It mainly affects professional divers who spend long amounts of time working in these conditions.

KennyM1 (author)joshiii922015-10-20

Not oxygen just compressed air and a plasma torch is much better these days

What he means is probably bone necrosis but that can happen with any kind of diving.

padawan101 (author)2016-09-25

looks SUPER Cool but for some reason the video is restricted for me :(

inspecter gadget (author)2016-08-29

howdy, you have a very impressive arsenal of innovative instructables!!! I was impressed with your thermal-lance... and others. As I too have in the past stumbled upon this characteristic of steel, while I was at my experimenting with a gas&hair torch at my engineering firm. I also felt compelled to publish an instructable, my first ;) I thought this may interest you? I'm sure you have seen it before as there are many on the web. Keep up the excellent work!!!! I G

Cool, I'll take a look.

inspecter gadget (author)2016-08-29


dlaing2 (author)2016-01-22

links on where to buy?

PipoL1 (author)dlaing22016-08-03

PipoL1 (author)2016-08-03

Please take a look:

CristianG44 (author)2016-06-15

im an iron worker and i need to cut some 1" rebar thats embedded in very thick concrete. researching thermal lances. your video was very informative!! very awesome. thanks!

StevenG21 (author)2015-12-08

I think you are bang on the money in regards to Thermic lance's basic construction , it's great to have some 1 to break down the DIY process , let's just call it a ( After Market Design ) especially for someone who is just starting out in engineering and needs to spend as little as possible for tools , well done.
If I can add my 2 cents worth from an engineers point of view .
Would a 12 v battery be good for the ignition process rather than a lighter?
Secondly how about making up a manifold for the disposable oxygen bottles right up to the point of running brass tubing instead of a vinyl hose and you could gang up 3-4 disposable oxy bottles incase of having a lengthy cut.
I may be wrong but I thought of a couple of suggestions that may work.
PS , did you trial run it I'm interested to know what was the th of material you were able to lance?
Regards Steven

BeachsideHank (author)2015-10-08

Very interesting method. I was wondering how to cut and shape profiles on railroad track when converting to an anvil design, this promises an economical solution, so thanks for posting it.

RussellG10 (author)BeachsideHank2015-10-19

question,did you ever work out the fastest way to cut RR track?..a recently closed down rail line has discarded some lengths of track,in a fairly remote area..Heavy as you know they are,it is NOT practical to move the entire length (impossible is closer to being accurate).so juice can be run,counting out transporting a gen.cutting torch or other such complications due to its remoteness ..any suggestions would be helpful..i considered a Thermite concoction and its still looking like the closest ,quickest and effective manner..then again,working out the proper amount of thermite to cut this much (very hard steel) is another problem altogether ...wouldnt want to have to travel out twice and put together 2 cutting mixes...anyway..Thank you

phb (author)RussellG102015-10-30

I work on the railways, in maintenance and work with the welders/track crew constantly.

To cut rail, they use demolition saws with a cutting disc (think of a huge angle grinder, with a cut off wheel and that's basically what it is) but they use a jig to attach the saw to the rail whilst they're cutting it. In that configuration, even though they're actually demolition saws, they're known as 'rail saws'.


Alternatively, if they don't need a neat cut, they'll get out the oxy acetylene torch and blow through the steel.

Thermite is, in my observation anyway, only used when welding a new section in, and isn't used for cutting rail. Given the temps it gets to it might be doable, but, personally, I wouldn't. There's too much potential for things to go really, really wrong

BeachsideHank (author)RussellG102015-10-19

No I did not, but I'd advise you to leave it alone, it is a Federal offense to remove or otherwise acquire railroad track without a bunch of documentation to accompany it, even scrap yards will turn you away without it. Long story short, no track section is ever "abandoned" in the eyes of the (U.S.) law, this goes back to the days of the old west when locals would appropriate some lengths for personal use- you can imagine the danger when a train expects there to be track where the is none, highballing along at night and then...

Just use a 9" [230mm] friction cutting disc in an angle grinder and remember that if the railroad track has had lots of heavily-loaded trains pass over it then the manganese in the track will have work-hardened. Try to get some new/er rail track if you can because it'll be a lot softer and easier to cut through and shape etc.

Thanks for those tips, I'll keep them in mind.

spiritwalker6153 (author)2015-10-13

I was wondering about the wisdom of using a vinyl tube for the oxygen supply. Is there something better out there?

KennyM1 (author)spiritwalker61532015-10-20

Of course there is you should use the oxygen hose from an oxy/fuel rig or just oxygen line they are green (in the united states)

Chakazuluu (author)2015-10-13

But in making repairs on the road with steel it seems that this process would burn the steel up & not make it weldable...

KennyM1 (author)Chakazuluu2015-10-20

Not for that purpose

Harriett Elizabeth (author)2015-10-20

brilliant and inspiring...will try it in the spring when have my workspace fully set up.

Bud in PA (author)2015-10-20

Where did you get the valve to connect the 1/4

Where did you get the valve ?

nickeyjoe (author)2015-10-16

You may want to replace your low surface area lance with iron or Al foam.

nickeyjoe (author)2015-10-16

If once you get this started, if you could convert to just air. could even pump in carbon fiber. The reaction's specific is the same regardless of reaction chamber. As the heat in the chamber goes up, lower concentrations of O2

nickeyjoe (author)2015-10-16

Looks hot. Like a good way to build a rock rocket. Burn two tunnnnel/ ava tubes in a rock. Have them intersect forming a "T". The right side of the cross bar is .1" the Left is .01". When the system is running flow water in the .01" hole. It wil ltravel down the .01" tube and explod when it hits the superheated rock at the intersection producing thrust out the .01" tube/tunnel.

Using this method you might be able to make very small, light extreamly controlable

An extension of this is a thermite rockes engine

isaac_alaska (author)2015-10-14

how much can you cut with a single bottle of oxygen that size?

carlos66ba (author)2015-10-13

Fantastic! One thing to do in my bucket list.

trike road poet (author)2015-10-11

Would this burn a hole through a cinder block for say, passing a pipe through? Or a concrete structure?

RandyS16 (author)trike road poet2015-10-11

Be careful, seen an experiment where the cinderblock exploded bc of water content and super heating...was not the intended result.

3967 (author)RandyS162015-10-13

can you give more information about this, do you have some links please?


lhunton (author)trike road poet2015-10-11

This guy cuts into concrete pretty easily. My guess is that since its actually melting the material that it should work just fine. Though messy and a masonry bit would probably be a lot cleaner and easier.

acarnes3 (author)trike road poet2015-10-11

I'm not 100% sure but it seems like a cinder lock could possibly break or be destroyed by something like this.

3967 (author)2015-10-13

hello, is this save to use without a

? gretings

rfitzgerald (author)2015-10-11

I once had a professor at college demonstrate the thermic lance to us. It was significantly larger at about 10 feet long and about 3/4" in diameter and I was so impressed! they told us they are quite well regulated in this country to prevent improper use (for robbing banks apparently, considering what it's capable of I'm not surprised!). As you say this one was connected to a larger oxygen bottle and lit with an acetylene torch. A very impressive tool indeed when he cut through a large block of granite in front of us I couldn't believe it!

A quick question, do you purchase a special type of brake line for doing this? I always thought brake lines were usually made of copper tube?

all brake line is steel. copper is much too soft to contain the pressures involved.

moon161 (author)handyhippie652015-10-11

Cupro-nickel cunifer metal is one exception to steel brake lines.

handyhippie65 (author)moon1612015-10-12

that stuff is interesting. i have to replace the lines on a 52 plymouth. i might just try this. thanx.

Brake line is copper plated steel. Plating on the outside prevents rust.

i am a mechanic, among other things, and i've replaced many brake lines, and never seen one that is copper plated. i've seen stainless steel, but never copper plated. it must not be OEM, or is a new technology. the newest vehicle i work on is 10-15 years old.

ben82brai (author)2015-10-12

Brilliant a real top idea, definitely on my agenda Benb

Razor 911 (author)2015-10-12

wow this is awesome thanks could be very usefull in the event where there is no power to use a grinder. Nice job

iusolivent (author)2015-10-12

Awesome! THX!

zappenfusen (author)2015-10-12

Is there any sane oversight of these comments?

antioch (author)2015-10-12

But does it cut through bank vaults and armored trucks doors?

kamalS14 (author)2015-10-12

That was very helping aid and important information keep up the good work

ironsmiter (author)2015-10-11

works wonders for cutting rough holes through heVy plate. You can see it a lot on some demolition sites, where they have to deal with structural iron.

"Professional : Amature after practice and a piece of paper with writing on it"


kwhit190211 (author)ironsmiter2015-10-11

At demolition sites what you see is usually not a o2 lance in operation. But, a long handle oxy/aceythlene torch in action. Be it a straight torch or the usual 90 degree head. Using a 02 lane to cut thin metal 2" and below is just to cost prohibitive. You blow through oxygen just to fast using just lance cutting.

About This Instructable




Bio: I like turning boring things into awesome things! Usually on video.
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