A typical resistance spot welder like this can range in price from around $200 to over
$800! That's a little out of my price range, so for this project let's make this one from
common materials, and for just a few bucks!
This modified transformer is the heart of the Spot Welder, and you might remember it
as the "Metal Melter". If this doesn't look familiar, check out how this was made, and
what it can do, in some of my other videos. I found a practical application for it in
making a spot welder like this one. To get started, I'm going to measure the base of
the transformer, and it looks like it's about 4-1/4" wide. I found a 6' piece of 1x6" common
board that will be perfect for this. Using my chop saw, I'll cut two pieces of the board
so that they're both 12" long, then another piece gets cut at 42". I'm trimming this piece
down with my table saw, so that it's about 1/4" wider than the transformer base, and
in this case that measures out at 4-1/2". Then it gets chopped into 3 different lengths
measuring 24", 12", and 4". Next, I found a 2x2 and am cutting the nicest parts of the
beam into two pieces measuring 13-1/2" long. 2 other pieces are cut at 4" and everything
can be placed together to see how it fits. That's the rough idea right there, and I'd
like to knock down the sharp edges, so I've found a 3/4" rounding bit and routed the appropriate
edges to give it a smoother feel. These front pieces are going to be my electrode holders.
The edge of this scrap piece of wood works as a template to draw a 90º angle into the
top piece about an inch from the end. I don't have a bandsaw, so I'm improvising with my
bench vise and a jigsaw to cut this piece out, and it worked. You'll see what this groove
is for in a bit. The next part is to cut out the pattern I drew onto the back panel, so
I'm going to utilize my vise once again, and use an 11/32 drill bit to cut holes in all
the corners so I can get back in there with my jigsaw. These holes will be for a switch
and a power cord, and all this panel needs now are two pilot holes drilled in the appropriate
places for the switch. I'm thinking I should give this a paint job, so all the panels get
sanded with an orbital sander, then laid out for priming and painting. I'm thinking black
and yellow. With the paint drying, I've gathered up a few components that were saved from the
same microwave I got the transformer from. To see all the amazing things I got from that
project, make sure you check out my video on salvaging a microwave I found in my neighbors
trashcan. I'm going to use the power cord, these wired spade connectors, the door handle,
and this contact switch. Aside from the wood, the only parts I needed to buy were a single-pole
light switch, with matching cover, copper offset terminal lugs, a couple of 1/4 thick
screws, 2 small nails and a length of 6 gauge solid copper wire. The copper wire gets marked
off in 1" increments, and two pieces are cut off using the wire cutter on my pliers. These
are going to work as my welding tips. The copper lugs have an adjustable screw that
can be loosened to insert the solid copper wire. When it's tightened back up it looks
like this. Alright the paint on the wood panels is dry, and I've added the switch to the back
panel to make sure it fits, so the next step is to flip it over and press the power cord
down into the hole at the bottom. The thick piece at the end of the cord prevents it from
pulling back through the hole. I'm ready to piece this back together, so I'm drilling
a couple of pilot holes into the bottom, and securing the back panel with a couple of screws.
Now the front 2x2 supports are added and the Metal Melter is placed on the base about an
inch back from the supports. I'll add a screw to one of the corners to help keep it in place,
and at this point I'm ready to rig up the electrical system. Taking the green wire from
the power cord, I'm stripping open a gap in the plastic to expose the bare cord. This
will wrap around the grounding screw on the power switch. The end of the wire has a hole
I can use to insert another short screw, and work that down into the opposite corner of
the transformer base. Not only does this secure the Metal Melter in place, it also grounds
out the transformer core at the same time. Ok, I've exposed the copper on the black wire,
and that will get connected to the bottom terminal of the power switch and screwed down
tight. This salvaged spade connector still fits onto one of the transformers primary
terminals, so with that on, the other end of the wire can be connected to the top terminal
of the power switch. Now the switch can be screwed down permanently, and a cover plate
added to protect from electric shock and make it look nice. The other spade connector that
was salvaged goes on the left terminal of the primary coil, and we could finish the
electrical here, but I want to add one more switch, for convenience. This switch still
has the original wires and connectors from the microwave, and I've just added a wrap
of electrical tape to make sure I don't get shocked while touching it. I'll strip the
end of the white wire, and twist it together with the other white wire coming off the primary,
then use a wire nut to cover the connection. Now the black wire is joined with the white
wire coming from the power cable, and the electrical system is complete. I added this
microwave door handle to the top panel and am screwing it on to see how it holds up.
The alignment looks good, and when I pick it up it seems to support the weight without
any problem. Alright, with the cables laying out the front, it's time to close up the side
panels, and I'm doing that by drilling holes and adding six screws on each panel, to make
sure it's held securely. The next step is to construct these electrode holders. I chose
to use a 3/16th bit to drill a hole into both tips of the 2x2's, which you can see got painted
yellow. The hole is big enough to prevent the wood from splitting when these screws
go in, yet small enough to hold them secure. This is the top piece and I'm going to add
the switch to the side, about 1/2" from the tip. It gets set at a slight angle and the
two small nails are hammered down into the holes already in the switch. Now the 2 beams
can be slid into the front of the casing, with one under the wire, and the other overtop.
To secure them in place, I'm using some scrap wood to keep them an equal distance apart
as I drill a hole through the side of the casing, and into the beam. I've pushed a nail
into the hole, and now you can see this top piece is able to pivot freely. It should be
obvious now why we needed that notch near the base. The bottom beam also gets a hole
drilled on either side, as well as it's own set of nails to keep it from sliding around.
The welding tips can be attached now, so we push one of the hex screws through the hole
in the lug, and then join it to the right side cable. That gets tightened securely into
our pilot hole, and all that gets repeated on the top. The misalignments can be fixed
by bending the lugs slightly inward, and now we've got perfect contact. To finish this
off, I'd like a way for the top beam to stay suspended on it's own. So to address the challenge,
I'll add a couple of screws and a thick rubber band. This system is finished! My very own
spot welder, and for less than $10 in materials. Let's see if it works. Power cord plugs in,
and with the electrode tips touching, I'll press the button to engage. But nothing's
happening. That's because the safety switch is still off. Let's try it again. This time
when I press the button, the system hums, and when the tips touch, I see the high-amp
sparks I was hoping for. I don't have any sheet metal handy, so I decided to try using
these washers for my first experiment. The pressure holds them I'm place hands free,
and with the system energized, it only takes about 3 seconds to fuse them together. I'm
trying it again with a third washer, being careful not to touch these, because they're
extremely hot. Surprisingly, it even worked on thicker welds like melting a washer to
this steel spike. Trying to break them apart by hand was a fruitless effort, so I tried
using pliers and even that was a bit of a challenge, but I got it. That just goes to
show the welds are pretty strong. A feature I really like about this design, is that the
electrode holders can be removed, allowing the user to extend the welders reach, and
access difficult angles. They go back in as easily as they came out, and all it takes
to secure them back in place is a little wiggle and the replacement of the locking nails.
The elastic band is easy to replace, and is doing a great job providing back tension after
I make a connection. I tried welding a couple of iron nails in an "X" pattern, and since
the heat was concentrated in the center, it didn't burn my fingers. The power of the Metal
Melter is still evident in the way the iron is boiling on this nail, and if allowed to
continue, the nail melts down into a little ball of liquid metal. When it's time to replace
the electrode tips, just loosen the tensioner, remove the spent electrode, and replace with
a fresh piece of your copper wire. If you do it this way, you can get 12 tips for a
buck! Because the wires not that expensive. Well now you know how to make my version of
a spot welder from easily accessible, and low-cost parts. If you liked this project,
perhaps you'll like some of my others. Check them out at www.thekingofrandom.com.