Back in 2012, the YouTube channel The King of Random posted a video on how to make your own spot welder, mostly out of parts scavenged from a microwave oven.
As I didn’t have a spot welder and could pick up a used microwave for under ten dollars, I decided to give it a try. The most time consuming part of the project was probably disassembling the microwave, mostly because I wanted more than just the microwave oven transformer (or MOT) when I stripped the microwave for parts. Once I had the parts I needed, it was time to rewire the MOT, which went pretty much as explained in this video.
Cutting the weld on the MOT, drifting out the transformer coils, replacing the primary coil, adding the heavy gauge wire, then epoxying the MOT back together were all accomplished with little trouble. However, since I don’t have a brother with a warehouse full of scrap, I went to a big box store and bought the 2 gauge wire along with some other components.
The main purpose in modifying the secondary coil on a MOT is
to convert the transformer from high voltage/low amperage to low voltage/high amperage.
This allows for high current which can be focused on a small point, enabling it
to fuse metal together.
The rest of the project was fairly basic wiring and
carpentry. I used the power cord from the microwave along with the power cord
standoff to supply power to the welder. I already had a light switch and cover
in stock, so I used those.
Rear view of the author's spot welder, showing power cord and switch. |
As suggested in the video, I used one of the door sensors and some wire scavenged
from the microwave as an activation switch on the moving arm of the spot
welder. This adds a good safety measure as the welder won’t send power to the
tips until I close that contact.
Side view of the author's spot welder. Note the switch on the top arm. |
Unfortunately, the heavy wire I purchased isn’t as flexible
as that used in the video, so I can’t separate the top arm to spot weld larger
or more awkwardly shaped pieces. Since I wouldn’t be removing the arm, one
change I made to the design was adding wooden spacers between the sides of the
main housing and the arm so that it’s less likely to twist or deflect when I close
the jaws of the spot welder.
The business end of the author's spot welder. |
I could have spent more time and effort giving the spot
welder a nicer finish or giving it a snazzy paint job like in the video, but I’m
more interested in function than form, and my home-made spot welder works just
fine even if it’s not as pretty as some others.
All told, I spent just over $20 on parts and supplies for
this project. It could have cost more, but I already had most of the items in inventory
or the scrap bin.
In Memorium: Grant Thompson, The King of Random, died on July 29,
2019. May he rest in peace.
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