Soldering with Hot Air

A friend mentioned soldering with hot air to me and that this is quite normal in the electronics industry. Must admit that I had not thought of it before.

hornplates and firebox

The hornplates and tub for my Burrell traction engine needed soldering together. I tried with a large 75W soldering iron and it was ok, but I was quickly losing heat out of the surrounding area.

The soldering iron is only 75W, but my paint stripper is a 1600W hot air gun. This is a very old Black & Decker unit that has been with me for over 28 years and 3 houses.

I insulated the parts being soldered from the mass of the metal vice using some offcuts of MDF.

insulating the metal parts from the vice
old soft solder flux

I’ve had this soldering paste for 20 years and I reckon my dad owned it for 20 years before that. We’ve only every used small amounts, but it works really still and so why not continue to use it?

I use a wooden stick to apply the paste to the hot metal. It rapidly melts and you can visibly see it cleaning the surface of the metals.

draper expert soft solder

Someone asked about the solder. This is my go to solder at the moment, bought at a local hardware store.

Looking at the specification online: Draper Expert SW3, 19227 250g Reel of K60/40 Tin / Lead Solder Wire.

The website says it’s no longer available and that will be because it’s a lead based solder.

I took my time heating the brass thoroughly using the hot air gun. You do have to be careful as the air gun is hot enough to set fire to the MDF. It will also rapidly burn you, so please be careful using this technique and wear protective gloves.

Once hot I applied the flux and carried on heating for a couple of minutes. I then applied the solder along the edges.

While the solder was still molten brushed the edges using a small steel wire brush. This removed all of the excess solder and lumps of solder from the joints.

An open flame can create any oxides on the surface of the metals. The hot air gun didn’t do this on these parts. This is a significant benefit. I will use this technique again.

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