I recently had a project that a spot welder would really come in handy for. A search on good ole You Tube yielded this plan by Grant Thompson that looked pretty good to me. https://www.youtube.com/watch?v=vrlvqib94xQ So I made one and I have to say it works pretty good as long as I give it time to cool after a half dozen or so welds.
This is the microwave transformer with the secondary winding removed and replaced with 2 windings of # 4 cable. View inside the box. Side view Business end with microswitch. This measures 1-1/2 volts across the contacts which would give 80 amps current minus internal losses. Not sure how often I will use the removable front arm feature but I can see how it could come in handy for certain tight places.
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I was going to add some pictures but it looks like that feature went away? EDIT: Disregard this post please.
Ok Don. I see what you have built and it is a great project, BUT I know you didn’t build it just because you could. Tell us what project you have coming up for us!!! I love all your projects whether it is the Tracker, charcoal tractor, or you wood chunkier.
I have been thinking of a project using a micro-wave coil also. That capacitor worries me. Were you able to discharge it using insulated pliers and how do you know if the insulation is good enough. I don’t mind getting burned while welding but I am no fan of electric shocks. I want to make an electro magnet using the coil. I understand the magnet when using DC electricity, but can you just plug the coil into an AC source. Will the coil dissipate the electric energy so that the wires don’t just melt? TomC
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HI Don M It looks simple and heavy duty,do you have an overload on the primary.I bet that will out last any of the so called cheap china models.next thing it could use is a screen on one side and computor fan on the other side too keep the heat down,the last battery charger i fixed,i installed a pop switch on top the transformer,with epoxy,to keep it from burning up trying too charge dead battery’s too long.
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Hi Kevin, It seems like the only place it gets hot is at the business end where the points touch. I did about 10 spot welds in 16 gauge metal and I smelled the heat of scorched wood where the lags went into the 2x2 arms.
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Hey Tom, I will spill the beans when I get a little farther along with my “project”. I bet I got more patience than you 
Thanks for the capacitor reminder. I never thought of it - but I didn’t touch it either. I think shorting it across with a screwdriver would be safe?
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Hey Don. If you want to dissipate the capacitor energy gently, take an incandescent light bulb base, install a low wattage bulb in it (ideally a 7 1/2 watt), and connect the two ends of the capacitor and you’ll get a short span light that drains the cap completely.
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I would use my Ruger 1022 at a safe distance…
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Cool project Don, I saw that a while back thought it was something I should have but like most things got put off till forgotten. Only thing I don’t have is a spare microwave. Coincidently the one he pulled out of the trash in the video is same as above my range.
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Help! I need to weld an alum wheel off the caddy or find another! When I hit that rock it bent the wheel, I bent it straight but it cracked!
I have some 4043 alum rod but it’s supposed to be ran with DC machine, mine is AC. I don’t have any other way to weld alum, what’s the different between AC and DC? When I try to weld alum with 4043 rod w/ my AC machine it just sparks like not enough heat so I turned it all the way up and same thing. Any ideas?
Has anyone welded alum with that 4043 alum rod??
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I welded aluminum with my ac/DC buzz box a long time ago. Don’t remember the rod. Seemed easy to weld. Heated it up first with the rose bud. Next burned the rod fast it goes. A rim might be a problem because of the size. DC is just like a battery current. AC is back and forth like house current.
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Thanks Jeff, my welder is 220, runs off of house current, does that mean it’s AC?
That 4043 is the only alum rod the store carried, it says on the package DC only, must mean it cause my machine won’t run it! My rim is only cracked about an inch long, from the outter most part down to where the bead sets on the inside. Can alum be welded with a AC stick machine??
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Hi Herb, I have always only used DC to weld alum. As far as I know it has to be welded DC whether it be stick, mig, or tig
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Ok, i know some plugin 220 machines are AC/DC like Jeff’s, I guess mine is AC only! At the risk of sounding ignorant can a AC machine be changed to run dc??
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Go on the net at youtube and I think you will find they have rod that you can weld aluminum with a propane / or map gas. If you don’t have a DC welder you have no other alternative that I know of. TomC
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Start searching around. Lots of folks have talked about welding aluminum DC vs AC.
http://bbs.homeshopmachinist.net/threads/41664-Does-aluminum-require-AC-or-DC-for-welding
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Hello brother Herb . Have ever thought about this?
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Thanks guys that was all helpful, Wayne that might be worth a try!
I do have my little 110volt Hobart, a guy gave me a few spools of alum wire years ago but l’ve never tried to weld alum with it. Does that work? What kind of gas would a guy use?
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Herb Here is a good youtube on welding / brazing aluminum.
/yhs/search;_ylt=A0LEVjVgRKRWxRcAeTCl87UF;_ylc=X1MDOTU4MTA0NjkEX3IDMgRmcgN5aHMtaXJ5LWZ1bGx5aG9zdGVkXzAxMQRncHJpZAN6SFhpNGtPcFJIYWIuNnEwYVBOSklBBG5fcnNsdAMwBG5fc3VnZwM1BG9yaWdpbgN1cy5zZWFyY2gueWFob28uY29tBHBvcwM0BHBxc3RyA3lvdXR1YmUgYWx1bWludW0gd2VsZGluZwRwcXN0cmwDMjQEcXN0cmwDMzYEcXVlcnkDeW91dHViZSBhbHVtaW51bSB3ZWxkaW5nIGFuZCBicmF6aW5nBHRfc3RtcAMxND
Opps! I thought that was awful long. Look it up. The guy was brazing the rear axle out of a lawnmower. That would be more like what you are doing than those guys welding a couple of thing aluminum TomC
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Hi Herb 100% argon for alum. I did forget tig weld alum is AC
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