I had no idea making a DIY welder would be so easy to do. And, it's pretty much FREE!

Additionally, the stick welder you get is definitely better than anycheap commercial welder you can buy.
Why is this homemade thing better than something you can buy? Because when you factor in shipping and labor and the little bit of retail markup - the companies that make typical cheap buzz boxes will skimp on copper as much as possible. Whereas you can use enough copper in this to make something really juicy, and still spend less, to nothing, compared to a store-bought arc welder.

So here's what you need to build a welder:
- Two beat up old microwaves
- Some 10 gauge wire
- Wire nuts

People throw out microwaves all the time, if you keep your eyes on the curbs.
Or, you can get microwaves at the local thrift store for $10 each.
Try the warehouse that processes donations - they have to pay to get rid of tons of broken ones.

Stuff you need for welding:
- Welding helmet ($16 and up)
- Welding rods ($6)
- Vice grip or purpose-built electrode holder ($6 for either)
- C clamp for grounding clamp
- Gloves
- Thick nonflammable (leather) clothing that will cover your arms

Disclaimer: High Voltage ELECTRICITY and lots of CURRENT! Heat, electrocution, and DANGER! You could die and you could go blind.

That said, try this at home!

See this for a lot of welding safety tips

Here are the really good how-tos that this project is informed by:
build a 70 amp welder
the tiny tim welder by tim williams
home made welding machine (via afrigadget)

Dan Hartman's how-to is good for reference, too.

And here's the quickest way to make a DC welder with a bunch of 12 volt batteries.

Step 1: Dissect the Microwaves

Invite your non-hardware oriented pals over to help help dissect your donor appliances.
They'll love it. David Grosof donated one of these microwaves under the condition that we take it apart together.

Good safety tip:
You'll find a gigantic capacitor inside the microwave. It looks like a metal can with two tabs on top.
Short it out to make sure it doesn't have any leftover charge on it, before you poke your hands anywhere near. Just put a screwdriver or something metal you aren't connected to, across the two metal terminals shown here.
<p>your fucking nuts mate.. fair play to you......</p>
<p>One thing you need to note is that newer microwave ovens have a solid-state switching supply which is useless for this Instructable. You need to get older ovens. How to tell? If the oven is lightweight, it is the newer type. So go for the heavy ones.</p>
<p>These are simple enough, but one thing I have not been able to come across is a DIYer addressing the current limiting. 10 gauge wire, even at 1000 feet is less than an ohm impedance, which would put your primary at 120Amps - way too much for a household circuit. Secondary windings should use even greater gauge and have even less resistance, that it becomes negligible. So the only room left to bring down the amperage must be the inductance/reactance from the transformer itself and the resistance of the metals you are welding, which is not much either. Unfortunately, I have not studied transformers in depth yet, and do not know what kind of impedance the transformer would have on the circuit. If anyone could help, I would appreciate it. I'm looking to make a 300A welder with a ratio of somewhere between 50:1 and 37.5:1 </p>
<p>If a microwave transformer is used, and the magnetic shunt is not removed, then there is current limiting. The magnetic shunt adds an effective series inductance which will limit current even if the secondary is short-circuited.</p>
<p>I guess I don't understand what you are asking for . 300A is pretty high output for a welder . Of all of my experience welding , ( 40 years ) I have never needed that much current . You don't clearly explain what you mean by &quot; ratio &quot; ( voltage ratio ? ) . If you want the welder to function , you will need 35-40 volts output . At a 37.5:1 voltage ratio , you would need to feed the primary with somewhere around 1300 to 1500 volts . ???? Anyway , try studying electrical theory , such simple things as Ohms law , Watts law , and Kirchoffs law , basic transformer theory is not that difficult once you get a handle on it . </p><p>Cheers !</p>
<p>yes, I am familiar with all of the basic circuitry laws. I have been collecting microwave transformers and have 4 or 5 now that I can use to build an arc welder. Your 35-40V rule helps. My predicament lies with the fact that professional grade welders (~$500 range) seem to go up to around 250A on a 120VAC (RMS) rail, which I want to duplicate.</p>
<p>My original comment was inquiring as to what reactance (which I have not studied much about) was limiting the power draw from the household outlet. 120V*15A=1800Wmax from standard circuit breaker. This translates in a perfect world to 1800W/35V=51.42A left for the transformer. This is where my problem lies - not enough.</p>
<p>But again, the 1800W is only acquired by some form of impedance (reactance, capacitance, resistance, etc.) which must come straight from the imperfections of the microwave transformers in every DIY arc welding tutorial, thus making values unpredictable. Else, the Amperage could be infinite.<br>Also, sorry to hijack this thread.</p>
<p>Duty cycle is an important consideration with welding machines , which would be really difficult to predict with a homebrew handwound transformer . In this article , the author checked to see if the transformer was getting hot . I guess it depends on how you plan to use the welder .This guy explains duty cycle pretty well for commercially made machines :</p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/X0ut4KRwP44" width="500"></iframe></p><p>Things to take into consideration . When welding , depending on what you are working on , chances are that you would &quot; burn &quot; a rod and lay down a bead , then let the metal cool and chip the slag . 30% duty cycle or even less should be adequate for most home projects . The authors transformers were in open air , if you put them in an enclosure ( recommended ) you may want to add a cooling fan . The temperature rating of the insulation on the secondary winding would be important too . Varnish coated &quot; magnet wire &quot; might be a better choice for the secondary winding rather than plastic insulated wire ( better heat transfer ) . But this project appears to work just fine , without a lot of cash outlay , I like it !!</p><p>Cheers , take care , and have a good day !...73</p>
<p>Hope you have had a chance to study up on Transformers. You will find that it is the 'Turns Ratio' that determines the voltage and current of the Secondary. </p>
For most transformer 'problems' like this, it's ok to consider PowerIn = PowerOut. So Vin x Iin = Vout x Iout.
<p>You are right but you MUST first have the specifications of the transformer secondary winding wire gauge to ascertain maximum load carrying capacity. You don't want a situation of the secondary overloading resulting in fireworks !</p>
<p>Voltage yes, Current is dependent on a lot of factors such as transformer inductance, resistance, frequency and magnetic flux coupling</p>
this is stolen from Grant Thompson, who made a much prettier one
<p>Another good safety tip would be not to try this at all. It is illegal in Australia, and I would imagine also in many other countries. There is a very good reason why, ONE mistake can kill you.</p>
<p>It is not illegal in Australia to work on electrical equipment (at least not in Victoria) that is not permanently connected to fixed wiring (eg powered using a flexible lead and plug).<br>There are restrictions on working on fixed wiring (eg house wiring) over a certain voltage (120Vdc and 50Vac) which then require a licensed electrician to perform the installation.<br></p>
<p>It must be the only state in Australia where it is not and I can guarantee that in Queensland it is. i agree with the voltage limits, but in most states it applies to everything not just fixed wiring. The minimum required is a restricted electrical licence. I also have doubts that it would even be legal to plug it in, as it is not an approved electrical device </p>
<p>So you are saying that we all need the government to protect us from ourselves? I can not stress this next point enough, &quot;I emphatically emplore you to speak for yourself. I don't want or need the government or anyone else telling me what's best for me. I can make those decisions just fine on my own. I also think it's a disgrace to come back here and try and make somebody else feel guilty or responsible for their sons death. Tragic as it is there is only one person responsible for his death and that is the deceased himself. nil nisi bonum but he obviously had no business messing around with electricity. It is probably safe to assume he shouldn't have had access to sharp objects, power tools and equipment, motor vehicles, motorcycles, chemicals, strong cleaning solvents or foods high in cholesterol. If he had never seen this instructable he was bound to fiddle with something sooner or later that would've killed him regardless. Perhaps putting other lives in danger as well. He should've kept his helmet on and stuck to fiddling around with his crayolas and coloring books. </p>
<p>The regs in Victoria changed again last year (2014) which does muddy the waters somewhat. There is a general statement in some of the documentation for Victoria that you have to be licensed or authorised (in some way) to work on appliances or replace plugs etc. but there seems to be no specific rules that can be referred to. The closest seem to be the requirements for appliances to be Tag tested and tested if being sold second hand or where required periodically as part of non-domestic use.<br><br>The application of the restricted license is for disconnection/reconnection of devices to fixed wiring.<br><br>Appliances sold to the general public must be certified but again, there seems to be no specific requirements for a home built device not offered or made available to the general public.<br><br>Having said all that, I agree that playing with equipment like this is very dangerous and, if something does goes wrong, you could end up in serious trouble or worse, dead. </p>
<p>To paraphrase my favorite lyricist ( Bob Dylan ) : </p><p>&quot; anything is legal , as long as you don't get caught &quot;</p><p>Cheers !</p>
<p>You live in a sad, sad nanny state then. </p>
On July 5, 2011 our son was accidentally electrocuted to death in our driveway. He was building, what we and the police believe to be this apparatus. The last website on his computer was this one and there was a microwave oven that was partially disassembled on his bed. He was not wearing gloves. He was 20 years old and is expecting a baby. The loss we have suffered is great. We feel that your site minimized the actual danger involved when working with such a powerful high voltage piece of equipment. Your warning disclaimer was followed by the statement: &quot;That said, try this at home!&quot;. Further down your site states &quot;Invite your non-hardware oriented pals to help dissect your donor appliances.&quot; Twenty year-olds tend to see themselves as invincible, and danger and death sometimes doesn't seem real to them. Your statement, &quot;You could die...&quot;, really did happen- to our son.
<p>and people choke to death in restraunts so the obvious solution is to: not eat in restraunts without proper training and adult supervision </p>
<p>This is an internet hoax by a sick individual.</p>
<p>Hoaxed by a troll. This never happened. Show me the news clip.</p>
<p>Hello Sandra .nunn</p><p>Being a parent , and grandparent myself , I am deeply saddened to hear about your son . I haven't posted any &quot; instructibles &quot; , but I have made comments to those who have , and always stressed the safety aspects of them . Working with any thing that is over 50 volts can be dangerous , and people should not attempt some of these projects without proper training in electrical safety , and should heed the warnings . BUT that unfortunately doesn't bring your son back . I don't know what to say at this point . </p><p>Take care </p>
<p>I feel so sorry for your loss Sandra ! May God rest his young soul.</p>
I read your comment about your sonshorrible accident and I am now deeply moved to express my deepest condolence. I am a father and my son means the world to me.. The loss of your son is a tragedy that hurts even to imagine. I will take this as a serendipitous lesson and will reaccess my aproach to safety. I will strive to be wise and to practice patience. Thank you for helping us. Farewell
<p>Regardless,this is not safe-I've been jolted with 50,000 volts working on a HE Ignition on a GM pick-up-it wasn't the shock that hurt,it was my head hitting the car hood after I got zapped.</p>
<p>I really fell sorry for your loss Sandra.</p><p>This project and others are inherently dangerous.</p><p>Only a fool will use a microwave oven transformer and they will put out around 20,000 VOLTS far far more than what is need for welding.</p><p>Also another stupid piece of very very bad advice from this poster is to &quot;short out&quot; the capacitor; YOU NEVER EVER SHORT A CAPACITOR. You can and most likely have an explosion. You have to either use a resistance load or say the capacitor is 12v charge light in auto stereo BOOM Cars use a light bulb rated for that.</p><p>Capacitors to put it simply is like a battery; where a battery is designed to release its charge SLOWLY a capacitor is design to release most of its charge very fast. Also depending on the capacitor type it can store THOUSANDS OF VOLTS and yo touch the terminals on a charged capacitor IT WILL KILL YOU...</p><p>This project and others I have seen are very very dangerous and a little bleep disclaimer won't fix that.</p><p>This web site needs to ether filter out these dangerous &quot;projects&quot; of put them in a &quot;restricted&quot; location on this site and to get into it you have to prove you know what you re doing.</p>
<p>you're just kidding right? </p><p>A capacitor's function is to maintain the voltage potential as in smooth out the ripple left behind when converting AC to DC a capacitor accumulates no more voltage than its charged with. An inductor on the other hand will - think magnito or choke. An inductor's function is to maintain current. The power supplies I made as a kid used a pi regulator where there was a cap in parallel after the bridge rectifier then an inductor in series followed by another cap in parallel. I played with 15,000 (fifteen thousand) volt transformers making Jacobs ladders. Adding homemade caps using window glass and aluminum foil sandwiched together. </p><p>Get it together and do some learning, I did. I ended up with 5 credits in electronics and had offers from HP and Raytheon, in Sunnyvale the summer between my junior and senior year. </p>
<p>Well AnonA2, it appears either you didn't read (or understand) the instructions or you don't know much about transformers. Very clearly Stasterisk describes how to <u>REMOVE</u> the secondary windings and REPLACE them with fewer turns and heavier wire than the primary. The output is now in the order of 35V.</p>
<p>Yes voltages under 50Volts are normally considered safe . If some idiot grabs hold of the mains connections , they will get zapped . The biggest concerns with arc welding is not electrocution , but thermal burns from the inherent heat ( don't grab hold of the metal before it has cooled ) , &quot; sunburn &quot; from welding without your body being properly covered , or eye damage from not wearing the proper shade of eye protection , a # 10 shade is normally what I have used . To people who weld , these are &quot; standard operating procedures &quot; . A novice probably needs a little training . </p><p>Cheers , take care , and have a good day !....73</p>
<p>I would advise any person who is not absolutely sure of how to work with AC or DC to ask a professional. They can both kill if attention is not paid to the project. Just take some time to understand Voltage (electricity), frequency Cycles/second), amperage (current), resistance (ohms), etc. It can be a fun project with a little care. Never be afraid to ask as terminology can sometime be frustrating for someone who has never worked with certain projects. No such thing as a dumb question.</p>
<p>There is no problem shorting a microwave cap. True they hold about 2,000 volts but the worse you'll get is a big flash and maybe a bit of black on yr screwdriver. Be careful though. This is not for amateurs. I'm a qualified and trained microwave engineer and was taught vigorously to make sure the caps were shorted out before any attempt was made at repair.</p>
<p>I love the simplicity of this welder and the clarity of the construction steps. Once I have a garage I am sure that this will be a weekend project. Then there will be many welding projects to follow!</p><p>As for accidents, safety, microwaves, capacitors, and high-voltage:</p><p>Accidents happen. If they result in death or permanent injury that is always sad. </p><p>Safety is primarily the responsibility of the person doing the work. Safety at its heart is common-sense guidelines on avoiding accidents. This fact is no comfort to survivors of egregious accidents, even persons who injured themselves non-fatally. We humans seek to place blame where our love is not already placed, and when someone we loved (or even KNEW) dies in an accident, it is even harder to accept the fact that the victim was at fault, or even that nobody is to blame at all.</p><p>Microwaves were likely chosen because of their ease of identification and their dispose-ability that makes them both easy to find and commonly available: I am sure there are many other devices with large transformers that could be used. The part of the microwave that makes it a microwave isn't used, so the magical mysterious microwave forces are not in play.</p><p>Shorting a large capacitor is common practice in the field, even though it is less sparky and probably better for the circuitry if one uses a resistor (like an incandescent light bulb). It is much safer to do this than it is to work on the circuitry with a possibly charged capacitor!</p><p>High-voltage... some comments talk about 2000 or 20,000 volts, but the transformers are modified to be unable to provide such voltages. I've worked on projects that are based on a &quot;flyback&quot; transformer that operate around 45,000 volts. You wear rubber gloves and unplug the thing (not just switch off) before making the next change. Voltage like that can arc across 2 inches, and I've seen it arc through some cheaper wire's plastic &quot;insulation&quot;. Scary, sure, but I learned that electrically charged air can be used to create lift, and the plasma glow is really pretty. My experiments and calculations yielded an interesting result: using this for lift takes about 1 kilowatt per kilogram.</p><p>Yes, it can be dangerous to build this Instructable. However, the hazardous-ness of a miss-used tool, even if said &quot;tool&quot; is instructions or plans, is DIRECTLY PROPORTIONAL to the tool's usefulness. You've never heard of any &quot;Handsaw Massacre&quot;, and handsaw accidents are usually just minor flesh wounds, while &quot;Chainsaw Massacre&quot; (fictitious but understandable) and chainsaw accidents often leave people with permanent injury or disability.</p><p>This Instructable is AS dangerous and AS useful as Arc Welding. It is still a valid Instructable, clearly follow-able and many people have had good results.</p>
<p>Very well said. Life, at times is dangerous. We learn and teach in order to mitigate that danger. One can pick up a commercial welder form a box store and stop their heart if they do something stupid. But you can do lots of stupid things. <br><br>Its a shame to see all of the negative and ignorant comments on here. </p>
<p>Oh yeah , </p><p>like I said before ,</p><p>A person needs to know what they are working with , and the dangers involved , before working with it . It kind of reminds me of an old 3 stooges episode , where they were supposed to be plumbers/pipefitters . Curly Joe took a conduit apart and said &quot; Here's why you can't get any water , your pipes are all full of wires ! &quot; </p><p>Cheers !</p>
<p>I agree . A person needs to gain some knowledge of what they are working with , and pay attention to what they are doing . I am retired now , but over the years when I was working , I was an electrician qualified up to 69,000 volts , a welder ( stick, mig tig with various metals ) , Machinist ( milling machines , lathes and other tools ) , operated heavy equipment , Chief engineer at an AM/FM broadcast radio station , worked with dangerous chemicals , Taught electrical/electronic theory to a multicraft industrial maintenance crew ( they all did well , I was proud of them !), and done a lot of other things too . Not bragging about my skills , just saying that I have been exposed to a lot of potential danger over the years . I have done a lot of things , and have NEVER had a serious injury , because I paid attention to what I was doing . Oh , I cut my finger a couple of times , put on a &quot; band aid &quot; and kept on working ! Yes , safety is a big concern , proper training would help a lot !</p><p>Cheers , take care , and have a good day !!...73</p>
<p>My daughter loves her welding class at school. Looks like a good father/daughter project. Thank you for the great work.</p>
<p>You are asking people to handle mains electricity, a 2000v secondary and a capacitor that can hold a charge for over 6 months without even a clea picture of how to discharge it. I attended a Microwave training course for a major electrical retailer in th UK and the tutors where nervous as the previous day a TRAINED electronics tecnhnian had been killed through not paying attention This project is moronic in the extreme as only trained people truly understand the danger of working with these transformers and capacitors and even they make mistakes. Another TRAINED technican fried his arm wth a radio transmitter. Stay away from these high voltage projects, you are totally irresponsible.</p>
where did you get 2000 volts? these are step down transformers. and there is no cap. he says numurous times the voltage is around 36v. this is essentially how most yesteryear welders were constructed. my old stick welder from the 70s is basically a multitap stepdown transformer with some cooling vanes and fan on it.
They are not on Microwaves they feed 12v to the heater and 2000v to the anode, this is the type of ignorance that makes it so dangerous. Also anyone testing a Microwave that has been scrapped risks radiation. I servced these for over 20 years I DO KNOW WHAT I AM TALKING ABOUT
<p>If you actually were a trained appliance tech, then you would also know that microwaves do not produce &quot;radiation&quot; My lord you must think everyone is stupid. Electricity is inherently dangerous in the wrong ( untrained unskilled unsafe) hands. I might know a thing or two. Twenty years in a cogen power plant, as a welder, electrician, pipefitter, and mechanic. Just sayin' be careful, and if you don't understand the workings of a microwave oven, you probably shouldn't be taking them apart.</p>
<p>Am a tech as well, but the Radiation part is False if its NOT POWERED! and its 6V for the filament(heater) and 1000V HT all AC volts after the diode and capacitor doubler you get 2kilovolt(2000Volts) its small capacitance stores less energy that you CAN SHORT safely!! Been Fixing these things for 25yrs! BUT anyone without electrical/electronic knowledge should Stay AWAY!!</p>
<p>This instructable is very cool and informative, but in this type of project you must be more careful to indicate that there is a very real danger here, in unexperimented hands it could lead to &quot;undesirable effects&quot;. Continue your good work!</p>
A good way to boost the output is to use 3 or 4 transformers.
This has to be THE stupidest article I've seen on instructables. It is my sincere hope that 'instructables.com' deletes this article. A guy I went to high school with died (on his birthday, believe it or not) because he accidentally touched a capacitor while working on a microwave. He left behind a wife and son, that was 21 years ago.
What is the polarity (current) on this thing?
<p>holy non bbc 2 word! you are crazy. You are not supposed to short out a capictator.</p>

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Bio: Hi! I'm Star Simpson! I'm a real me! See more at [http://stars.mit.edu stars.mit.edu]. photo by [http://bea.st ... More »
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