Here's for interesting discussion. I was talking with someone about Thermite when I ran across this. "Although the reactants are stable at room temperature, when they are exposed to sufficient heat to ignite (usually by igniting with a burning magnesium ribbon, but other methods are used as well, such as potassium permanganate and glycerine, or a sparkler), they burn with an extremely intense exothermic reaction. The products emerge as liquids due to the high temperatures reached (with iron (III) oxide, up to 2500°C (4500°F) although the actual temperature reached depends on how quickly heat can escape to the surrounding environment). Thermite contains its own supply of oxygen, and does not require any external source such as air. Consequently, it cannot be smothered and may ignite in any environment, given sufficient initial heat. It will burn just as well while underwater, for example, and cannot even be extinguished with water, as water sprayed on a thermite reaction will instantly be boiled into steam. This, combined with the extremely high temperatures generated, makes thermite reactions extremely hazardous even when appropriate precautions are taken. "The thermite reaction can take place by accident in industrial locations where abrasive grinding and cutting wheels are used with ferrous metals. Using aluminium in this situation produces an admixture of oxides which is capable of violent explosive reaction." I use my bench grinder for all kinds of metal and I know I have ground aluminum and iron on the same wheel. I don't clean around it very often so I know there is a decent size pile of aluminum, steel, iron, brass, etc around the grinder. Just curious if anyone has ever heard of or experienced a fire from it? I realize the risk is probably pretty low, but the point is I never heard of it at all before now. Anyone else?
Problem lies with particle size, density, and Al/Fe ratio. I wouldn't be worried UNLESS you switch between the two often and let a pile of really fine dist accumulate behind the grinder! I did set some steel wool on fire with a grinder, rather interesting, but I wouldn't want to do it again! Thermite leaves an iron (or alloy) deposit -- very useful for dropping down gun barrels (to make the useless) and to weld broken railroad tracks together!
You should only grind ferrous metals on a bench grinder (at least with a grind stone). I have no idea about the thermite (other than that scene from Star Wars when they walked into Jaba The Hut's bar, and pulled out the handheld thermite bomb to make a point. "Bwaha. This bounty hunter is my kind of scum!") Anyway, non-ferrous (no sparks when grinding) metals will load up the wheels. It makes for an un-even grind when dressing steel, but it also makes the wheels off balance, and at worse can cause the wheels to be so off balance they'll come apart (explode!) at high rpm. Since most bench grinders are set up somewhere between dick and gut high... -Brad
When i was in school someone in a beginning sculpture class thought they would grind the aluminum with a grinder then go grind some steel welds down. Yeah it exploded. I told them it wasn;t a good idea, but they didn't care. Person was fine, but alittle scared. Anyway thermite sounds like it could be cool to watch burn if it was under control.
Cool info, and always wondered the same thing after first hearing about it. Dad has an old thermite grenade from the military, used for dropping down the barrel of another tank? Might have to talk him into setting it off...
had a little chunk of it go up on my chop saw--wasn't particularly exciting (wasn't alot of build up) coolest thing I ever saw was a moron use a cutting torch over a chip tray on a rotor lathe--imagine a REALLY REALLY big sparkler. and yes, it had to burn itself out. fire extinguisher just sorta compounded the situation.
That was AWESOME!!!! Jeezus, that makes me want to start finding metal shavings from all the brake and machine shops in town! -Brad
How, why and where would most of us come across Thermite. I've never heard of it so I don't think I've got any in my shed.....have I? Pete
I worked around the stuff for over twenty years before I retired from BNSF, we used it to field weld rail together. The only explosion I ever saw was intentional when one of the guys on my crew tossed an aluminum and slag overflow ingot into a creek from a bridge we were working on. It blew water and mud a good 40 feet into the air and we all got sprayed with the junk. Well...you have to keep yourself amused at work somehow.
Call almost any chemical supply house. They'll have powdered aluminum and powdered iron that you can buy. Nice clean pure stuff. These are used for many different chemcial reactions, for certain chemical tests or sometimes as references or standards in the lab. Put the iron oxide out on an open tray in a humid environment until it is good and rusty. DRY THE IRON POWER IN AN OVEN. Mix with aluminum powder then figure how to light it in a safe place without it exploding. Really folks, this isn't anything to mess with. Aluminum powder (especially the high grade "prepared" stuff) is NOT that stable and shouldn't really be messed with. Oxidizers can set the aluminum off in a big way unexpectedly...no match required. -Bigchief.
Pretty much anyone tinkering in a shop has the components. It just takes an ignition source. Agreed that it is not something to be playing with. You could burn your shop down. The result is that once ignited NOTHING the average person has around will extinguish it. You'll have molten iron spitting everywhere. Its an unquenchable fire that can burn under water. Pouring water will only make it more violent like a grease fire. I had no idea about the risks of grinding aluminum. My bench grinder is a tiny one, but it is about the height of my nads. The thought of grindstone shrapnel hammering the family jewels is enough to make me give it a second thought.
I've wanted to make thermite since I was about 11... But, Im not sure how "legal" it is to make this shit... I think it's a pretty serious offense... Also, if you have a legit thermite grenade you should probably try to get rid of it... I'll take it... hahaha... But seriously, those fuckers are dangerous... You saw the video... But even more seriously, I'll take it... By the way, that TV show looks cool as shit.... I guess it's English or Aussie...???
I first posted a warning about mixing metals in a polishing / grinding shop a long time ago. There is no safe formula. Piles of mixed filngs, swarf, or buffing dust only have to reach the right mix at any one point. a little moisture and you're in trouble. I saw a dust explosion probably 28-30 years ago in a polishing shop. 5 dead. If you hit aluminum with the right abrasive, it will spark. It's quite freaky too as the grinding wheel get's the sparks going into all kinds of orbits. How ever,telling people where to source the necessary chemicals to make thermite is nothing short of damned irresponsible. I don't believe we have any members of Al Quaeda on the HAMB, but advising people you don't even knoow, where to source materials to make bombs on the internet is dumb.
My High School Chemistry teacher lit some off for the class. It was a pile about as big as a plain M&M, in the middle of a litter box full of sand, and he lit it with a magnesium strip. We all wore welding goggles to watch it burn... It was impressive. When all was said and done, one lucky student got to take home the ball of glass that it made; It was the size of a softball!
OK, OK, OK the secret is out. We're busted. Now EVERYBODY is gonna have the stuff in their back pocket. Down boy! We're not giving out the plans for an atomic bomb here... All it takes is enough brains to type the word Thermite into a Google, Yahoo or Answers.com search mixed with a teensy bit of resourcefulness and any halfwit dumb enough to try and light this stuff off can find what he needs to torch a hole halfway to China. If they can find the HAMB, pictures of tits (nice ones even) and the formulation of a dozen grades of gasoline on the Internet in less than 15 seconds then they're surely capable of finding anything they want to know about just about anything. ...including the mis-use or malicious use of dangerous materials. ....all without any help from us. -Bigchief.
There are no large chip piles in a clean shop. Chips in a mill tray or power hacksaw tray are soaked with coolant, taken out every day, in a clean shop. When a grinder stone comes apart while grinding aluminum, it breaks in pieces, but doesn't 'explode'. The flying debris is no danger, if you wear goggles or face shield, etc. Dynamite is more efficient; bigger bang, less work.
The reason why grinding wheels can and do explode is many of them use aluminum oxide as the core abrasive. Silicon carbide is probably the most popular but aluminum oxide is being made in both larger and finer grits all the time. We have it in one form or another from 26 grit through to sub micron. Heat build up is the other reason. Try throwing cold damp polished pebbles into a good camp fire.
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