home made super dooper hot knife

[CPT. SPRINGINGTON]

this is going to be a write up on how to make one. This will take me a couple days since I'm working long shifts right now.

If you decide to make one and you are a noob to electronics, be extremely careful. This website or I is not to be blamed for your, uh, disasters.

I'll keep this straight forward... steal your moms microwave and open it up.



you want this thing on the right, it's a transformer. I also pulled the fan to keep the transformer cool in the new box.



you don't need this, but the magnets on it are always useful.



be very careful with this capacitor, mine read something like 2600 volts. This link tells you how to discharge it.
http://www.partselect.com/microwave+dis ... repair.htm



more to come...

[ChaseTruck754]

Looking forward to the rest of this!

[Rmc]

What's it gonna be for? A tire grooving iron?

[poolman]

No pics from the emergency room? lol

[Rmc]

Hahaha! Wheeew...

[Travisfab]

DO NOT EVER TAKE APART A MICROWAVE UNLESS YOU KNOW EXACTLY WHAT YOU ARE DOING!!!!!!!!!!


Microwaves by far are the most dangerous appliance in your house, this post should honestly be deleted. Unless you have been trained by a professional, do not even consider doing this. 1 slip of a screwdriver and you are in the hospital. Not worth it.

[CPT. SPRINGINGTON]

I agree with travis. Microwave transformers can be bought on eBay for cheap, already removed.

as far as deleted that could be debated both ways. this kind of modification is already all over the internet.

Yes this will be a tire groover. I want to be able to take out large chunks and I don't want to pay $400 for a good unit. Technically you can build this for free, but I'm going to buy a couple parts.
Also what I'm doing is not new, lots of people use power transformers for lots of things, you can even make a welder with them. I think I'm just the first person to make a write up on how to make one for a tire groover.

back to the project; you need to remove the secondary winding, if you look closely you can see there's red wire winding in the center, remove that too.




I used a cut off wheel to cut 1 side then punch the wire through. Supposedly you can also grind the welds off the housing and a side will come off, then you can slide the winding off. Either way it will take a few minutes of work.




you want it to look like this, be sure you don't damage the primary winding. After this, I'm going to the store to buy some 4 or 6 gauge insulated wire. Technically jumper cables would work for this next step too.

[Rmc]

This is getting good...

[Travisfab]

All I have to say is some things are worth 400 bucks.

[Rmc]

Lol well isn't a mis-wired exploding capacitor photo worth a thousand words?

[SteveG]

You guys gotta admit. Our resident Capitan posts the stuff no one else will. I don't know anything about taking apart microwaves, but if El Capitan says to be very careful, you can be sure that it is some dangerous sh$&.

We might need to create a section just for the captain. "Dangerous DIY for Dangerous People."

[hobbyturnedobsession]

You also have to admit so far he knows exactly what hes doin.

[CPT. SPRINGINGTON]

Here's the transformer, all you do is wrap the wire around it. I wound it 3 times. Depending on the power output I might have to remove 1 loop from it to lower the amperage output.
Jumper cables had too thin of wire, so I skipped those. Local department store only had aluminum wire in the size I wanted, so I skipped that, but I've seen other people use it.
I ended up using starter wire, which I think most auto parts stores sell. I only had about 8 feet. This wire is going to be like the lead wires on a welder, so 10-15 feet of wire will make things easier.
I also got a light switch with a dimmer built in for the on switch and it controls a portion of the current. Its rated for 600 watts and technically you should use one that is rated for 1500 watts, but I'm going to be cautious and I'm only going to do a set of 4 tires anyways.

more to come

[Rmc]

So your dimmer switch is the current potentiometer got it. Now why the extra loops through the transformer? Does it change the output current max dependent on number of loops? U gonna connect the fat red ones to the transformers primary winding? How do you guage the power output? Fire it up n see if the insulation melts off before u touch the inductive coil your planning on making? I guess I'm making sence I don't know... What are u gonna use for the blade?

[CPT. SPRINGINGTON]

correct on the potentio.
Loops are the voltage. say if my house is supplying 120v and the primary wire has 120 loops, each loop on the secondary represents 1 volt. So it will put out about 3 volts. It's the amps where I'm still learning. If my house outlet is 120v and 12amps, 120x12=1440 watts. So secondary you do 1440 watts divided by 3 volts = 480 amps...

now that I'm doing math... if I have a 600watt light switch at 120v, that only supplies 5amps... with the switch mine will probably put out just under 200 amps.

Which will still work... how much amperage you need depends on the thickness of the material you're heating up.

I went to college for DC but not AC electricity, so I'm not quite sure if the transformer will try to pull more voltage through the light switch to make up for the lack in amperage, as it would with DC. But by the look of other peoples projects, I'm going to assume not.

[Rmc]

Ya I'm not shure on that one, I work with multi tap transformers and industrial ac but I've never delved into the theory behind transformers. I mostly deal with Plc type logic circuits.

[wayfastwhitie]

Less windings should give you less resistance and more wattage, same goes with the length of wire and wire construction/gauge.

[CPT. SPRINGINGTON]

wattage stays the same, amps and voltage will go up and down. amps up volts down, amps down volts up.

I didnt make a box yet and just wired it together. It all works, even the switch works beautifully. BUT my cutting blade is too thick, so my wires are heating up hotter than the blade. I might even have to make a foot on/off pedal to try and control the hot wires, but first i'll try making a thinner blade.




here is my blade I made in 5 minutes. The U part is the only part that heats up because the current is limited to that area between the wires. The rest of it can heat up but only from soaking up the heat, which would take awhile.

[CPT. SPRINGINGTON]

well, the transformer setup works perfect, I just have to find the right kind of blade, I should probably order the real tire grooving blades on eBay.

but I said screw it and ground a knife edge on a saws all blade and went to town, very easy, but a lot of vibrating and you have to sharpen the blade after about 1 tire.