Introduction: Tomato Cage or Wire Spot Welder Using Microwave Transformer

I have a large garden and grow lots of Veggies that need tomato cages. They really take a beating,get caught in tiller, get bent, Welds break and to use them they get bent more, more welds break etc. And the prices to replace seem to be just getting out of hand.

I try to build all my projects with recycled parts, So this project cost me $0, I build 1 part at a time, then go scavenging for next needed wanted parts, sometimes I get something totally different, Usually for the better.

I got real interested in building one when a site "" showed a person in a foreign country that I could not understand the language or comments that followed. Watched several more other related videos, Where have I been? I was really impressed! However trying to spot weld 2 wires balancing on a ground wire was just not going to work, So this one is different as I used real heavy copper lug ends from real big old buss fuse for contacts, Tore apart an old microwave oven and salvaged transformer Modified by removing secondary wires adding welding wires, A power cord and assorted wires. Attached some boards to build base, Added an old push to start power button, Tested made a couple small changes, When repairing the tomato cages you must lightly sand to get good contact or else the wires just get hot without welding.

Please do not ever power up Magnetron

Please do not power transformer before the "LETHEL" secondary coil have been removed

You should wear some kind of glasses

Wear gloves as the welds stay hot longer than one might think.

Step 1: Modify Transformer

There are two ways to remove secondary, one is by cutting off with hacksaw and drilling inside part out. this leaves the core in original condition, I did not choose this way as one slip with the hacksaw......

The other way is to cut the two opposing welds with a dremel or abrasive blade then pry E and I apart. Remove secondary and primary coil , It took some effort as they are in pretty tight and are shellacked at the factory. Some duct tape was used to insulate the replaced primary coil, My vice and small blocks of wood were used to seat the coil

Then use a short length of welding cable as it is very flexible ( I did not measure as it was what I had). Two wraps around core keeping as tight as reasonable. I used a stainless steel hose clamp to hold the E and I part together. (I will be using some epoxy at a later date to hold the E and I together) Then soldered a bolt lug to each end. Testing with a meter showed 2 volts and 7 amp draw. Now onto the actual welding part.

Step 2:

I needed some sort of heavy copper to make the contacts, so I started hunting my original in my head ideas was the copper bolts from an old starter Solenoid, However on another treasure hunt found an old electrical panel that used to power this place up to see what was there, Picked up two huge old fuses that had escaped scavengers, Perfect..... Took them apart cleaned the copper using salt and vinegar and some stainless steel kitchen scrubbers, Went on to build the levers, roughly drew out pattern I was looking for, cut on band saw, and sanded, Using the thickness of the copper lugs as a guide. Used a sharpie marker to shade part that needed removed then trimmed the inner side and outer of arms so the lugs would match when closed. Then roughly drew out the trimming and drilling that needed done on the copper. Because I was going to be fusing wire I did not want it pointed so used a hacksaw to flatten the top edge. Used a file to form an X shape which didn't work well and had to later file parallel groves so they would bite into the wire. Drilled 1/4 holes at the end of the arms, used a long bolt and two large washers only on each end no center washer (needed no side way play) Attached the copper to the arms, Had to shim the back of one so the tips would line up when clamped shut, Attached two short welding cables with lugs attached ( taken from a battery bank no longer used) I recommend soldering all the lugs as the crimped ones get warmer than the soldered ones. Removed the copper that extended below as there was going to be a base attached later. Used Zip ties to hold cables from moving next to lugs, Assembled all parts as shown in last picture.

Step 3: Final Assembly

Added a 36 inch 1 X 6 for a base, screwed down the electrode assembly, then transformer. Attached a momentary start/stop button, It was taken from an old roller controller that used to operated 3 phase warehouse heavy equipment, It has two buttons one always on the other always off. In testing sometimes the electrodes would stick, The off button removes power while the on button momentarily supply's power. Wired in series fit the bill. Used the original microwave power cord . Attached start button to base, cleaned up the wiring insulated exposed wires with tape and shrink tubing, I was going to put on an antifreeze jug to hide the electrics when Found a 5 gallon bucket that the bottom had froze halfway off, Used the table saw to remove top and bottom ribs from bucket, Took inside to measure how much I needed, cut using table saw then drilled holes and attached cover, Finally as I was cleaning up, the handle from the bucket was screaming "use me"... "use me..." Project now has a handle. Watch the videos at the top with welder being used, they are very short but straight to the point. Figuring how to put videos on you tube was my hardest part. The welder weighs just shy of 20 lbs, is 30 inches long and 7 inches high. Nothing was purchased except the solder, zip ties, tape and shrink tubing. My recycled parts were used throughout. When being used it is heavy enough that it doesn't slide around. I will be adding some sort of removable bolt on regular pointy spot welding like tips at later date So this could be used like a regular spot welder. If I had to build another one I think it would be just like I built it. providing that similar parts were available, Thank you for reading this far, Any tips or suggestions are always welcome . Please consider voting for this.

Build a Tool Contest

Participated in the
Build a Tool Contest