Retrotechtacular: Solder Like Its 1944!

When we first saw this 1944 US Office of Education film about hand soldering, we figured it might still have some good information. Well, perhaps it does, but the 1944 soldering was with a giant iron, and the work looked more like metal bricks than anything we’ve soldered lately. Of course, the physics is all the same, but some of the terminology, like “sweating in” isn’t anything we’ve heard before, although we have heard of sweat soldering.

They do show some electronic soldering on components, including some interesting-looking coils. But the irons look more like a bad science fiction movie’s idea of a lightsaber. The solder is equally huge, of course.

If it Smells Like Bacon…

We liked the soldering iron holder with a magnifier — or maybe it is just a piece of shield glass — that the lady in the movie uses. It would have made a perfect vent hood, too, but in 1944 we are guessing you were encouraged to sniff the fumes. They mention not letting wire fly into your eye, but they didn’t cover safety glasses until well after that part. Not a word about lead safety, either.

The tip on the iron is bigger than most of the screwdrivers on our bench. Other than the scale, we didn’t find much to disagree with in the film. After all, soldering is soldering regardless of the size of the solder joints. Of course, the real excitement comes at the end when they start using a flame to do some bulk soldering of some enclosures.

To the Stars!

If you want a perspective from a decade or so later, check out the NASA soldering film from 1958, entitled “Above and Beyond” that we’ve seen before. You get to follow Harry who, “Oh yes, he’s a ham radio operator.” We aren’t metallurgy experts, but we think, by now, someone understands why solder alloy melts at a lower temperature than its constituent metals.

We’ll warn you, you might see yourself in some of the bad examples which, luckily, aren’t exemplified by our ham radio friend Harry. The soldering irons and tools used look a bit more familiar in this video, including a vintage pair of thermal strippers.

If you think these videos are at the dawn of soldering, you might be surprised. Apparently, humans have been soldering at least as far back as 205 BC.

37 thoughts on “Retrotechtacular: Solder Like Its 1944!

  1. Periscope Film is a treasure trove. So much beautiful & ridiculous old military and industrial gadgetry. Lovely standard broadcasting accent narration. Hand-painted title cards. Glad that channel exists

  2. I knew a lady who used to build aircraft radios for Hallicrafter during WW2…and she said they tested the radio first before soldering anything. I.E. each resistor/capacitor lead was wrapped around the terminal strip so no solder was needed. Of course it made it easier to replace errant components but the main idea was not to let the lead and tin be the only thing holding the part. After radio passed vibration test they soldered everything.

    1. When I learned to solder it was drilled into me that solder was not to be used to mechanically fasten components or wires. Mechanical fastening was done by firmly wrapping the wires.

      1. Soldering is still used for mechanical connections – just not with delicate electronic components! It’s being used as low-temperature brazing when serving as a mechanical bond.

        1. Every SMT component uses solder as the mechanical connection as well as the electrical. And the resultant boards are incredibly g-tolerant and jerk-tolerant, far more than you would ever expect.

          1. Less mass, less inertia. Those SMT connections don’t have to hold much. It’s a different world from what’s going on in that video.

            It’s still good to understand how to solder those old point to point, bulky items. Those techniques will give you longer lasting connections when you solder the non-tiny stuff like the wires, connectors, switches, variable resistors and other controls that still need to interface with your modern PCB covered in SMT components.

          2. Not every SMT part. Many SMT inductors and electrolytic/aluminum caps will happily rip themselves off of PCBs. Sometimes they take the traces with them and sometimes the solder joint breaks. I’ve seen both. The same with larger SMT integrated circuits. Of course we don’t need to worry about it with the smaller parts, but they are so small that mechanical connections are never really considered at all.

      2. Yes. Although, for installations that aren’t going into a spacecraft, a bouncy military vehicle or otherwise need extra mechanical stability but are going to be frequently modified (like a HaD project) sometimes it’s advisable to do a little less of that.

        Perhaps wrap around the tab but don’t go through the hole, or do go through the hole but don’t wrap. Just go straight through, solder and trim. Same goes with bending leads up against the bottom of a PCB for through-hole construction vs not.

        This way it’s easier and quicker to desolder later. It saves you time and frustration and also reduces the amount of heating on the part during desoldering perhaps preventing component failures.

  3. The example is still valid for heavy gauge power cables.

    I have 2/0 battery cables in solar/battery systems at a remote ham radio site and on an RV. The cable is a flexible one for welding, and has about a thousand strands. You can’t just crimp the terminals on, the strands will creep out of the crimp. To crimp them, I first dip the cable end in rosin, and then dip it in a solder _pot_ which I have fed a _bar_ of solder. At this point the terminal can be crimped and will hold.

    Smaller – but still large from a modern perspective – cables are soldered to the terminal using the journeyman soldering iron in the example.

    1. If the strands are slipping, you are not crimping with enough force. A hydraulic crimper will squeeze with enough force to cold-weld the strands together and to the terminal giving a mechanically and electrically superior joint. Crimping after soldering will fracture the joint leaving it prone to fatigue.

        1. > Plus solder has a much higher electrical resistance than copper.

          Why don’t you measure that and get back to me ;-)

          Actually, it can’t possibly matter what the resistance of a really thin bit of solder is vs. copper. This would only matter to a hi-fi tweak, and those folks can hear stuff that doesn’t exist.

          When I solder something, I am going for mechanical stability. Crimping usuallly works, but we have all had crimps fail, most of us don’t really have the best crimpers, and some of the claims made for crimping seem overstated. Like “cold-wellding”.

          On the other hand, lots of people make poor solder joints.

      1. Actually, this was with a hydraulic crimper. Gets to about 12 tons. 1000-strand copper welding cable still flows after all of that.

        I think “cold-weld” is an overstatement. There might not be any air left in the connection, but it’s not anything like welded and will still flow if I don’t do anything about it.

        Crimping after dipping the whole thing in rosin and then a solder pot might fracture the joint, but one wonders why the softer solder fractures and the harder copper does not. Probably they both flow somewhat.

    2. That is so, so wrong. I crimp lugs on class K stranded #2, 2/0, and 4/0 daily without issue. Solder cold flows under pressure resulting in a bad connection. Wire should never be tinned before crimping.

    3. You might want to solder after crimping as well. Solder is subject to ‘cold flow’, wherein it continues to deform and change shape very slowly when it is compressed. This continued deformation of the solder causes the joint to loosen with time, possibly causing a point of failure or even becoming a fire hazard. (That’s one of the reasons why lamp cord is no longer tinned before being screwed down, although the very tips may be tinned to discourage strand separation).

      Of course, the cold flow may be exacerbated by thermal cycling, which is likely to be an even bigger problem in high-current circuits.

        1. I just read that and it was not so much cold flow as shearing the zinc and the outer ring of wires and poor bond between the wires and the zinc due to the wires being galvanized and thus zinc mill scale covered when brazed in. This would leave voids and invalidate safety calculations.

          Furthermore, it should be noted that while steel has a theoretically infinite fatigue life, that is violated by the usage of zinc, and then violated again by exceeding the base design load through heavy retrofits. The engineers involved probably failed to recalculate and account for all the things prior to retrofit. Or presented findings to management and were told to yolo it. Perhaps due to lack of knowledge of prior failures to meet specification.

    4. I use welding cable in the aux house batteries in my RV and I use a hydraulic crimper with the proper sized die, and I have never had a wire creep out of a crimp. You are doing something wrong with your crimping.

  4. I’m not sure what’s with the smug sense of superiority in this article; these techniques are still completely valid. “Solder fumes” are just rosin vapors, and contain little to no lead. As to lead safety, just don’t eat it! Simple as that. Maybe the author just wanted to tell everyone that he can solder small things. Congratulations, I guess.

    1. Probably not much of an issue for the hobbyist that solders occasionally.
      I’m not sure burning a bunch of tree sap near your face is that much different than doing the same with tobacco leaves, just less addictive. For an every-day on-the-job solderer I would think it would be similar to having a smoking habit. And if you are one of those who is still unconvinced that is a bad thing… well I guess we should just be happy you figured out which end of the iron is the handle.

  5. i kind of think the space theme of the second video is kind of out of place. especially considering the apollo guidance computer used welded components and a wire wrap backplane. solder wasn’t good enough.

  6. “They do show some electronic soldering on components, including some interesting-looking coils. But the irons look more like a bad science fiction movie’s idea of a lightsaber. The solder is equally huge, of course.”

    It’s not a bug, it’s a feature. 🙂
    The big soldering iron tip is no problem for applying solder to wires.
    If that’s the main task, then it’s a good choice, even. A tiny soldering iron tip has no advantage here, rather the contrary. The big surface makes the whole procedure easier/quicker, I assume.

    Speaking of those grenade looking coils..
    Big components like those coils aren’t a bad thing per se, depending on the wavelength (big), they can perform excellent.
    Ancient spider web coils have an high Q factory, for example.
    They run cycles around our punny modern day alternatives. 🙂

      1. Well I have heard of sweat soldering, but that has a very specific meaning and, yes, it is often used in pipes. With jewelers, it is a very specific technique where you precoat one piece with solder and then reheat to melt it and stick on the other part. In plumbing, it seems like it is always done with a torch, but I don’t think you usually preapply the solder.

        But I don’t know any of that for sure, that’s just what I remember from way back.

  7. I don’t know about you safety-obsessed nancy kerrigans but lead is DELICIOUS, especially when you make it into lead acetate (I use it to sweeten my wine). I season the lead beads with rosin smoke, too. Like a good smoked ham.

    All seriousness though. Stay away from the acid core flux for soldering, the fumes give me a hardcore headache 🤒 (sick emoji test)

  8. Neat post. I had two soldering irons before I was 12, and am probably up to 8 now, plus a couple of torches.

    About 10 years ago, I bought a mint condition, carton-sealed-with-wax, new old stock Chinese military HF tube transmit/receive set circa 1968. It came with a field maintenance kit which included a small iron hammer intended for heating in a fire… to make solder repairs. Maybe some year I’ll try it.

    1. An iron hammer… interesting.
      Any old HF tube type radio equipment is automatically very cool.
      In relation to welding equipment, old technology with it’s heavy transformers and chokes will run rings around the new inverter based technology machines any day…all day…and night…non stop. Literally. Yes the inverter gear is much lighter and maybe a bit more efficient, but when it comes to duty cycle and brute reliability the old heavy metal units and all their copper will be working long after the lightweight stuff has fried out it’s semiconductors.
      I had a mobile tool set for fixing Harley Davidsons once…it consisted of a hammer and a bigger hammer…

      1. The arc welding kit we used in the 80s when repairing locomotives was easily from the 60s. Huge and oil cooled with a duty cycle that was immense. Even new for the 80s transformer based welders couldn’t keep up with it.

        However for low duty light work stuff at home inverter based welders do the job.

  9. Some years ago I was involved in clearing out an abandoned army base. The mission of the base was battery and communication research. On the top floor of one of the bomb-proof buildings was a large room with long tables with separate soldering stations. At each station was a small sign “UNPLUG IRON BEFORE LEAVING STATION”.
    The coolest thing was a pile of old Radio Electronics magazines left in a corner of the room. They went back to the early 1950’s. There was easily 50 to 100 of them. All tube theory stuff.

  10. A ‘not so smart’ idea that R.Bosch used in the w123 Mercedes climate control board was soldering the blower relay to a ‘circuit board’. Every time the fan came on…it gave the ‘lower contact (NO)’ a tap. After 7 years of ‘tapping’ the solder joint ‘fractured’…
    all it took was removing old ‘brittle’ solder
    and added some fresh lead/tin. I got a cheesecake for that discovery…

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