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DIY Soldering Gun? Answered

My 40W soldering iron is a bit too weak. I've been thinking about making a soldering gun, but it confuses me a bit...
Since I don't work with sensitive electronic components, I don't think there's a problem. I also like the fact that I can control the amount of heat easily...

I soldering gun is pretty much a "mix" between a soldering iron and a welder, right? Similar to a hot-wire styrofoam cutter. Maybe I should call it an Incandescent soldering lamp... 
A hot wire cutter is exactly like a soldering gun, except it uses a thicker, shorter, wire that has low resistance...

To make one, what I need is a power supply that can supply: High current, and low voltage (Wikipedia doesn't define low voltage), right?

With a 5V 40A ATX power supply, a switch, and a single core wire that has close to 0 resistance, do you think I would be able to make a soldering gun? A 5V ATX power supply is the power supply with the lowest voltage that I own. 

I don't know the resistance of the wire that I can use, because I don't know what wire to use, and don't know the current it will take. I know I will need the heating wire of the tip to be a higher gauge, so it will have more resistance on high amps, and it will be the one that will heats up.

From what I'm guessing, 5V is too high, and something like 1V would be better. Perhaps I'll find a way for stepping it down to a lower voltage...


There is a Wikipedia article titled, "Soldering gun",

The usual recipe for a soldering gun is an electric transformer,

with a 1-turn secondary winding. The primary winding is connected, plugged into, to the mains power.

I do not, at present, have precise numbers for turns ratio, or the voltage and current in the secondary winding. Numbers for voltage and current in the primary winding, you can get from reading the spec plate, on this soldering gun, if you've got one.

Also the Wikipedia article for "Soldering gun", linked above, mentioned a patent number, USP2405866, and that patent might disclose the numbers we are wondering about. I haven't read it yet.

You know, a soldering gun is not a super expensive tool.

I actually have that model, linked above. Although, I kind of had to modify it a little bit to make into a tool that actually works.

Of course, now that I have mentioned that I modded the thing, I should probably up some pictures of it...

I'll attach those pics as a reply to this post.

While you're waiting, you can read Mr. Weller's patent for an "Electrical heating apparatus", uh, here,

By the way, Weller's patent, US2405866, does reveal some of the numbers you were wondering about, and these are mostly contained in one quote,

"...Primary winding 26 of the transformer is designed to use 115
volt alternating current, although, of course, the invention is not
limited thereto. Leads 27 and 27a connect the transformer to conductor cord 28 attached at any suitable source of electrical power not shown. Transformer secondary winding 30 is designed to furnish 200 amperes at one-quarter volt. In one satisfactory embodiment the primary winding 26 includes 880 turns of #27 wire while secondary consists of 2 turns of #5 B. & S. gauge."

So there you go. The secondary winding is designed to give 200 A at 0.25 V, and the product of those two numbers is 200*0.25 = 50 W

The turns ratio for this this "satisfactory embodiment" is thus, 880:2 = 440:1

In the approximation that this transformer is an ideal (lossless) transformer, this gives, 0.4545 A at 110 V on the primary winding, and 200 A at 0.25 V on the secondary.

Regarding wire size, note that B. & S. gauge, Brown and Sharpe wire gauge, is today more commonly called American wire gauge, or AWG, and it turns out Wikipedia has an article for AWG, here,

and there is a table in that page, listing resistance per unit length for different AWG sizes of copper wire, and that table will come in handy, since you were wondering about electrical resistance in the tip of the soldering gun; i.e. the part of the circuit where electric power is being dissipated as heat.

Recall the current and voltage of the secondary winding were 200 A and 0.25 V. Supposing all of that power is real, dissipated as heat, if it were a lumped resistor dissipating that heat, its resistance would be 0.25V/200 A = 0.00125 ohm = 1.25 milliohm.

In the approximation that all, 100%, of your power dissipation ( heat) goes to the tip, which is the same as saying the tip is the only part of the circuit with any resistance, I can imagine the tip, as a resistor, and I can use that table for copper wire resistance from the Wikipedia AWG article.

For example a 15 cm length of 14 AWG copper wire, has a resistance of

(0.15 m)*(8.286 milliohm/meter) = 1.2429 milliohm

For a perfect design, all the electrical power (100%) is dissipated as heat at the tip, for a practical design, most of the heat goes to the tip. I don't know how much that will be in practice. Greater than 50% would, technically be most of the heat.

I would guess, it would be practical to make a secondary circuit for which 90% of the resistance is in the tip, plus 10% in the secondary winding and connections. Also guessing the transformer could be 90% efficient too, at delivering power to the secondary circuit, for total efficiency would be around (90%)*(90%) =81%, for delivering electric heat to the tip, but really that's just hand waving guestimation.

200A @0.25V? Uh-oh...

The best cheap ones that I could find were these, which can supply ~12A max.



This chart has a ton of info about AWG: http://www.powerstream.com/Wire_Size.htm

If I used, for example, 20AWG wire, at 10cm in length, I would have 0.00338333333 ohms? At 1V, would that be 333A? I don't think so, I think I'm getting something wrong...

I don't really want to make a transformer. I think it's way to difficult for me with my knowledge.

Well, I kind of think the easiest way to get a soldering gun would be to buy one, if they exist for the mains power in your country, wherever that is.

Actually, I just looked at the link RickHarris posted a few days ago, for that Maplin brand thing,


and I do not know what that thing is, but I am convinced it is NOT a soldering gun. To me it looks more like a heat gun.

I am confident soldering guns made for 220 VAC, 230 VAC, mains power exist, although I don't know if they're easy to find, or cheap...

Examples, both from uk.farnell.com

Cheap brand, Duratool(r), £10.56


Weller(r) brand, £56.35, costs five times as much, for some reason.


I read the Wiki article. I wish I had Harbor freight where I live...

If I bought one on eBay, I think I'd find one for ~25. If I bought one where I live, I doubt I'd be able to find the exact same one for under $100...

Ok tell us where you live and that will make answers a lot more applicable.

I don't think it matters, since I can probably get all of the parts on eBay.

So, I promised some pictures of the evil things I did to my soldering gun.

In fairness to HarborFreight(r) Tools, I should mention that this soldering gun (HF item # 04328) worked really well, when it was brand new, a few years ago.

Also most of the problems I had with it, seemed to occur after the first time I replaced the tip, and it is important for me to note, this new tip was a homemade one, made from 10 AWG copper electrical wire, not one of their factory-made tips, made to fit this soldering gun.

So, I guess that was the first mod: a tip made from 10 AWG copper electrical wire, about 15 cm in length. Using a hammer, I flattened the hairpin-shaped turn, the part that touches solder. Although, in retrospect, I kind of wonder if that actually changed the cross-section area, and thus resistance, of that part. Maybe I was just trying to copy the shape of the factory-made tip. (You can see a picture of that on the product page for this soldering gun, linked previously.)

The second mod: I replaced a plastic piece that supported the two big conductors, in the place where they exit the body of the gun.

The reason why I replaced this plastic piece, is because it was getting hot enough to smoke and char. Pics 5 and 6 show what is left of this plastic piece.

In place of the plastic piece I wraped some woven fiberglass cloth, the kind sold for patching holes in cars, around the big conductors.

Then, on top of the fiberglass cloth, I put a layer of RTV silicone seal, to sort of slick down the stray glass threads, and secure it all in place.

The reason why I specifically chose fiberglass and silicone, is because those are materials that can withstand moderately high temperatures.

Anyway, this bundle of fiberglass and silicone, it does seem to stand up to the heat, and I have not had any problems since with melting plastic.

While I am commenting on this soldering iron, I should mention the hex-shaped nuts that hold the tip in place. It seems to me this method for holding the tip in place, and connecting to it electrically... it seems to me this part of the design could be better.

To get big current flowing through the tip, those nuts and the connections underneath them, have to be clean and tight. In fact if you're ever using a gun similar to this one, and it is on and humming, but the tip is not getting hot enough, those connections, the nuts holding the tip, those are probably the part to check first.

In fact I think I tinned, put a layer of solder on, the ends of tip that go under these nuts, and I think it helped keep that connection clean and conductive.

I don't actually remember how I tinned that part of the tip, but I probably used a propane torch, like the kind used for soldering copper plumbing fittings.

I mean, in a previous comment here, you were saying something about your soldering iron not delivering enough heat, and that's why you wanted a soldering gun. Well, I think the next step up from a soldering gun, in terms of more heat, is a propane torch. I mention this just in case you were wondering about that.


Awesome, thanks for the pictures!

Now you're making me want one evn more...

I hope I've provided enough information. It just looks like a big mess to me...

Even if it doesn't turn out perfect, I think I can learn quite a bit from making a project like this...

I have never been a big fan of the soldering gun, too clumsy. As far as I know all of the guns I have seen use a bit of heavy gauge copper wire as the tip and pass a chunky current through it to heat it up.

you would need temperature control to make sure you didn't melt it.

What do you solder that needs more than 40 watts?

I've never used one, but I looks like it's easier to use.

I think my Antex (from eBay) doesn't reach a high enough temperature for solder that doesn't have lead. My other cheap one died a few months ago...

However, if my soldering iron won't fail on me, I might be able to make a project that will win the first (or grand!) prize in the Lamps & Lighting contest.... If it will, I'll have to use my dad's old 20W Weller...

When soldering thick wires. When I tin the wire, it takes so much time, so the insulation starts melting on some types... I hope to use make a more powerful one, because I don't solder enough for it to justify buying a good one... I can also make my own tips for a soldering gun.

Melt what, the wire? I'll have a some kind of switch wire in series with the wire. I'm pretty sure I'll find one that'll be able to handle the current.

Yes melt the copper wire bit on the soldering gun.

I have a weller and an Antex although the temp controlled weller gets the most use. It is designed for lead free solder so gets very hot if I need it to.

So far I haven't had any issues although like Iceng I hate lead free solder, as a teacher we had to use it because of health and safety regulations. Yuck!

I think you will find a temp controlled iron a lot more versatile than a soldering gun.


At least in the UK a soldering gun can be very cheap.

I just looked at the product page you linked to for this, "Maplin Soldering Gun Solder Iron", and it looks very strange to me.

I am somewhat troubled that you, and others, are presenting this thing, whatever it is, as a "soldering gun".

In my experience, a soldering gun,




is this sort of heavy, gun shaped thing, with a u-shaped tip. The reason the gun is heavy, is because it contains a transformer. The reason the tip is u-shaped, is because the tip is part of an electric circuit. The reason it gets hot, is because it has big current flowing through it, 100s of amperes typically, if I can believe the numbers in Weller's original patent. Dang, I just used the word "reason" three times! Well, you know, it's all very, uh, reasonable.

In contrast, the Maplin product you linked to: What is that thing?
The tip looks like black plastic. What is the heating mechanism? Is it blowing hot air? Like a heat gun,

I don't know, man. I thought we were all on the same page on this one. Maybe not. Maybe not.

You know, I think Weird Al got it wrong too. In his song, "White and Nerdy", there is this lyric,

I ain't got a gat but I got a soldering gun


But if I look closely at the official music video for the same song, linked below, at around t = 1m+5s, you know what I see? Well, I tell you what I see. I see a soldering iron, not a soldering gun.

Yeah. Truth. I think Weird Al lost some nerd-cred there, just a little.

In fairness, this music video, as a complete work, is overflowing with other shining, and accurate, examples of nerdiness. For example, there really was a "Star Wars Holiday Special" (see t=2m+29s), and this video was probably where I learned about that film's existence for the first time.

Moving to the UK!

If I inhale the fumes from lead free solder, I get horrible nausea. I'm not sure, but i don't think I have a problem with leaded solder.

I'll just hold the trigger when I want to solder, like a hot-glue gun (In the way that I push the trigger (or switch) to use it when I need it...)

That's because lead-free solder has a much higher melting point. The fumes that come from leaded solder are actually just the flux (which shouldn't contain lead). It's still considered an irritant but it isn't as dangerous as lead. I do all of my soldering outside so that the wind will blow away the fumes.

Depending on how you control the current/ or not you may find the tip goes from cold to red hot in a fraction of a second! Manual control may not be an option. Remember that a relativly small tip hasn't the area to dissapate the heat very quickly.

Also for unsoldering big components, such as relays, and big electrolytic capacitors. Those take forever to ulsolder

You are better off with a temp regulated station.
Mine has only 40W but goes from 150-420°C, enough for bigger electronics parts.
Once you have to unsolder heatsinks and similar it is best to use a hot air gun on the big metal parts first to warm them up.

I wanted to attach a 220V lamp dimmer...

I usually just break the circuit board, or give up, if I see that I can't solder a bi component. I'd love to have a hot air gun (for shrinking shrink tubing too), but I'd use it only a couple times a year, so I don't think it would be worth it...


1 year ago

A year or so ago I was in the same position as you, needing an iron. I had a Velleman 3 in 1 lab kit that had included everything needed for entry level electronics: 2000 count Multimeter, basic LM317 supply, & a decent 55W temp-controlled iron.

It has had a rough life, and through both negligence on my part as well as poor design on its part, basically everything on it has broke more than once. Velleman did not offer any economically repair options, so I did a lot of repairs on it myself. I discovered that the yellow Elenco iron was identical to the iron on the Velleman, and that replacement was pretty cheap. However that replacement didn't even last a year, so I gave up with dealing with all the problems that kit had, and went and bought a more professional iron, the Hakko fx-888d.

However In the meantime, I was literally using low value resistors as soldering irons! I took the dead iron apart to see what about them kept failing, and got to see the engineering that went into it. Soldering irons are, as expected, very simple devices. Not much more than a special soldering tip shoved snug into a steel shaft, with a special ceramic heating element then shoved inside of that. The heating element is as close to the tip as possible. The real difficulty of making a DIY iron with limited household materials was finding materials that had the correct thermal, electrical, and structural properties needed. The ceramic heating element essentially a bar of some sort of ceramic wrapped with nichrome wire, and that is then potted in even more ceramic. In mine, there were 4 wires coming out of the ceramic heating element, 2 for heating, and the other 2 for the thermocouple or thermistor. Often the failure mode of these heating elements is the wire breaking internally, or the ceramic cracking due to physical shock (like accidentally dropping the iron. Oops! :P ) Then the plastic used to hold the entire soldering iron shaft to the rest of the handle is also a bit special. It appears to be a either a very hard epoxy mold, or a molded fiberglass reinforced ABS thing. In other words, that ain't no regular cheap plastic!

So in short, if you want to make your own soldering iron, you will need to figure out how to get the materials that can safely withstand high temps while still providing structural integrity, dielectric strength (electrically insulating), and good thermal transfer I don't know of any common household materials that do that.

Thanks, what I'm looking for is to make a soldering gun, not an iron. I've broken a ceramic to see what was inside once.

Oh, a soldering gun! Somehow I missed that! :P well that is essentially the same thing. I don't know much about them, but you probably will need a higher resistance wire. Look into the tips sold for them, to see what material they are made out of. Most of what I said would hold true for them as well.

A soldering gun is essentially exactly the same as an iron, with a minor difference in operation and ergonomics. Due to the way the heating element and tip are one-in-the-same, soldering guns can be made in higher wattages and deliver more heat.

However, a soldering gun is nowhere near the realm of welding. Welding is an entirely different process.

I was talking about a soldering iron. I myself have also tried to build one. The problems in bold are what I discovered on my own.

I forgot to also mention what to do about a tip. The tip on any soldering iron is generally a nickel plated copper-alloy. It is primarily copper because of its good thermal conductance, but copper by itself cannot be used because when heated it quickly oxidizes, and can no longer reflow solder properly. I learned this when I tried to use a thick copper wire as a soldering tip.

If you must, then you can get away with "tinning" the copper tip and using that, but it will not last long and you will find yourself constantly needing to scrape off corrosion and crud.


1 year ago

You can look into buying a cheap hakko knock off replacement iron and building a soldering station around that, that would probably be a fun (but advanced) project! I recommend using a temperature controlled iron for good solder work and to save your tip's and iron.

While in some cases temp-controlled irons are not necessary (as the case with the well designed unregulated irons like the old fashioned Wellers, that instead rely on thermal mass and reaching a thermal equilibrium with the ambient air) for small electronics is is basically a must. Especially with modern cheapo soldering irons not having any appreciable thermal mass.


1 year ago

Viewing the soldering on your ibles looks good to me. I suspect you are using lead free solder which has a higher melting temperature and probably accounts for the need of a 40W iron..

I use a 25W for most of my work and a 15W princess iron for SMD ICs but I use 60/40 tin/lead solder that melts at 188'C almost exclusively... There are times that I need to use an indium/lead/silver based solder that melts at 154'C and even lower indium/tin 118'C for fired circuit traces on ceramic substrates where leaching would be an unacceptable problem or metalized mylar applications...

BTW a hot wire cutter using a 1/8" welding rod, cut styrofoam with 23_amps at 9_volts AC.


Correct. The soldering iron that I used died a few months ago died.

Antex, the one I have now is the problem: I think my 40W Antex (from eBay) doesn't reach a high enough temperature for solder that doesn't have lead. The solder doesn't melt into tota liquid form, and solidifies on the soldering iron...