How to Make a Spot Welder

Written by jessica reed
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How to Make a Spot Welder
Store bought spot welder. ("Spot Welder." [Online image] Available, 4 Jan. 2009.)

A spot welder is an essential tool for any welder or mechanic. It allows small areas to be welded easily in your home workspace. For those who understand welding and wiring, it's possible to build your own spot welder at home, which means there is no need to buy an expensive commercial spot welder. You'll get the personal satisfaction of working with a machine you created with your own two hands, and you'll save a lot of money by using components you already have in your own garage.

Skill level:

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Things you need

  • Microwave oven transformer
  • Saw
  • 4 foot 4-gauge grounding wire
  • Plywood
  • Bolts
  • Drywall screws
  • Copper pipes
  • 8-gauge copper wire
  • Drill
  • Springs
  • Offset cam

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  1. 1

    Set a microwave transformer so the secondary coil is on the top and the primary is on the bottom. This should usually be when the transformer is set on its base. Use a saw to cut the secondary coil off. Be careful not to cut into the primary coil. Wedge out everything from the transformer except the shunt and the primary coil.

  2. 2

    Push the ends of a 4-foot piece of 4-gauge grounding wire in through the slots where the secondary coil was. Bend the wire around and push the ends through the sides opposite of where each entered. Bend around the front and feed back through the opposite slots again. Keep winding until you have three or four coils. Let the ends stick out the back.

  3. 3

    Create the jaws of your spot welder. Use a long piece of plywood as your base. Use two pieces of plywood, one thick and one thinner, and attach them on their sides to the base. Push the screws through the base and into the boards to get them to stay. Leave just enough room for your copper pipes to fit snugly inside.

  4. 4

    Attach the bottom copper pipe using drywall screws. Drill holes in the copper pipe and screw it to the base, making sure one end is snugly inside the boards you built in Step 3. For the second copper pipe, insert a small piece of plywood to separate the two pipes. Use a spring under the top pipe. Attach the top pipe at the back of the boards by putting the screw in sideways. This allows the copper pipe to swing down on the spring. Use an offset cam to push the pipe down. The spring will cause it to open back up.

  5. 5

    Install bolts in the end of each copper pipe sticking out from the wooden base. Make sure to align them directly above and below each other so the tips touch when the top pipe is pushed down. Attach your microwave oven transformer behind the wooden base holding the copper pipes. Push the ends of the coil you created into each of the copper pipes. Use 8-gauge copper wire to wrap around any exposed and unconnected wire from the coils to the copper pipes. Apply power, and your spot welder is ready to go.

Tips and warnings

  • Never leave any wires exposed. They can create a shock that can be deadly.
  • If you have never worked with wiring or welding, do not attempt this at home.

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