On the surface, the spot welder is a simple device. If you release enough current through two pieces of metal very quickly, they will heat up enough to melt and fuse together. However, as with many things, the problem lies in the details, and building a suitable spot welder requires both solving these details and paying attention to the basics.

We haven't shown any of our friends on [Make It Extreme], where they have as many build tools, and they also use them to build other things, if not more. However, we expect this sturdy-looking spot welding opportunity to appear in future videos because it looks really good and works very well. The electronics are seemingly simple-just rewind the microwave oven transformer and a simple timer switch to control the current pulse. Ingeniously, they used a pair of transformers to greatly increase the current-they estimated the current to be 1,000 A, allowing the machine to weld materials up to 4 mm thick.

With the completion of the electrical end, the rest of the construction is concentrated on the housing. The key to high-quality spot welding is the solid physical pressure between the electrodes, which is provided by the lever compound connection and the long solid copper electrode. We have to say that the sweep of the lock handle looks very ergonomic, and we like the way the handle is closed to activate the current pulse. Extra points for the appearance of the finished carbon fiber. The video below shows a demonstration of the build and what it can do.

Most of the spot welders we have seen are downstream in the food chain and are specifically used for welding battery packs and so on. However, we do remember another very professional spot welder.

I was moved by the narrative and mentioned that my own spot welder is a very old business unit, and I put a 555 timer in it...

You could have used it, oh wait.

Look for Amana ovens made in the United States. The oldest magnetrons are less efficient, so a monster transformer that easily cuts off the high-voltage secondary is used to make up for it. The earlier ones usually have larger transformers than the newest ones. 1500 watts. Lothar iron core.

But some old "tanks" are still running. Please don't slaughter a running one.

Because if it is still running now, if you take good care of it, it will still be running decades later. This is something that modern equipment cannot do... These old, high-quality and repairable objects are hard to argue with. Use, when junk modern things can provide good enough parts but can’t really be repaired, it’s such a waste of things you can repair...

Oops, my refrigerator is older than mine, and it is still intact (although its status light is broken, I haven't had time to consider replacing it) but the newer one (but out of warranty) needs some repairs, now all The internal rails and plastic are damaged, and every time the ambient temperature rises and the pump tries to run, you can hear the sound of its dying...Although the rated efficiency is high, it does not seem to reduce a power pig...

Decades ago, Consumer Reports warned readers not to buy "efficient" furnaces, because the higher maintenance costs and frequency of maintenance outweighed any savings.

This is the best spot welding video I have seen so far. I have been collecting some microwave oven transformers myself, but have not yet started making spot welders. I want to know whether to connect two of the secondary windings in series or in parallel. This video is very clear.

**Good and reliable** Other mandatory details of the spot welder (built on this basis in most cases) are the timer and the mechanism for applying force after welding is complete (rule of thumb: keep the fixture closed until the red dot disappears. Premature exercise may weaken the weld)

Those "Fotek" relays directly from China/Ebal/Amazon/etc. are mostly fake. If you buy the 25A version, then you are lucky to have a 10A TO220 TRIAC inside. Lots of YouTube videos about these.

However, complete spot welder timers are also common in Ali/eBay/China. They have impressive triacs, but given the current status of suspicious electronic products in China, I'm not sure if they are worth the money.

One thing I would do differently is to add a foot pedal, or at least there are some simple ways to add a foot pedal as an additional accessory. Before spot welding, two hands are usually required to position the part. If necessary, a foot pedal with a slight clamping force can even be used as a third hand.

The foot switch problem could be solved by the slave/assistant/7-year-old daughter-available at the time. But yes, sometimes they are not there, so the foot switch will be very convenient.

If I want to change anything, it is to improve the connection to the cable. A single grub screw may be sufficient, but a super clamp or bolt crimp may be better. In addition, voltage, current, and resistance are measured, and some adjustments may be made and some graphs are drawn. But it boils down to the nerd rather than the welder...

You have to be quite prolific in breeding to always have a 7-year-old daughter, and at that age you may only have 6 months to remember the extra half. As we all know, this is rounded to 8... it sounds pretty good. Expensive for me, time consuming and noisy...

So no one will comment on the drilling and tapping of transformer cores?

This is my idea! But it looks like he has polished the outer core of the core, which may weaken the effect anyway (this is why he may need two stages in the first place!)

I have a smaller commercial (cheap imported) spot welder. Pop the circuit breaker on the 20A circuit each time. A small series resistor had to be added. Can't imagine what kind of wiring he has to allow him to run two microwave transformers. The inrush current is large. In addition, the cost of 3 feet 1 inch copper bars is twice the cost I paid for the entire device. Ouch.

I also want to know-it looks outrageously expensive. Of course only the contract needs to be copper? Using solid copper to make those huge arms seems to be burning money.

110v is an American thing. It is 230v in Europe and there is no problem running any welding machine from a residential plug. (Technically the rated current of the plug is 16A, so it is about 3600W, but a high-quality socket/plug will definitely cost more, especially in the short term, using a 20A circuit breaker is about 4400W, which is more than enough for rod welding or tig welding .

uncertain. My 200 amp welding machine and plasma cutting machine are plugged into a 50A 220v socket. It may not be necessary for the entire 50A circuit (this is the standard for American welders), but I would not say that a 20A circuit breaker is sufficient. A 200 amp welding machine is not very big either. Most amateur-grade MIG, TIG and stick machines have a maximum capacity of 200 amps.

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