FREEZING WEATHER, FREEZING garage. Ah... the joys of winter restoration work. But at least there's the heat from the welding torch. Better spin this bit of body repair work out a bit longer.
Get the floor-pan nice and red, then warm the hands for a while. Well, that's one distinct advantage of gas welding over MIG, MAG, TIG and all those other fancy named electrical boxes.
The other advantage is the versatility of an oxy-acetylene set. As well as welding steel and aluminium, it'll braze, solder, cut, shrink, free off rusted nuts, light cigarettes...How curious - that floor-pan has suddenly taken on a peculiar curved shape. Surely it was flat before? Most odd. Presumably that's what they mean by distortion. Unfortunately, distortion is part and parcel of gas welding.
Dealing with it successfully is what distinguishes the expert welder from the rest of us. Most home restorers can make two pieces of steel stick together and will probably produce a joint that's plenty strong enough for the purpose. Anticipating how the metal is likely to move, and then hammering the weld in just the right place to correct it, is another matter entirely, though.
If you're thinking of investing in a welding set, it's worth noting that professional restorers always use oxy-acetylene in preference to MIG for visible areas of bodywork. Although gas welding isn't as quick or as easy, the professionals like it because they can hammer down the welds. A MIG produces hardly any distortion but the weld is a hard, raised bead which can't be dressed. On external panels it must be ground off - and that weakens the joint. A gas welded joint, on the other hand, is soft enough to be planished, and a pro can work on it with hammer and dolly until virtually no body filler is necessary. There's a real art to this, of course, but the basic skills can be acquired with practise.
Playing around with scrap panels is probably the best way of learning how to manipulate hot, twisting steel. It'll be found that butt joints tend to close up after the first few tack welds, and that these have to be spread by hammering in order to get the edges back into their original relationship. If an attempt is made to weld a long joint in a single run, straight through from one end to the other, the steel will bow and the result will be a curve - useful if that's what was wanted, pretty disastrous if it wasn't. However, once understood, this shrinking effect can be used to advantage - without press tools it's about the only method that's available to the amateur for making double curvature repair-panels.
Proper oxy-acetylene welding sets currently cost from around £300. That will buy the trolley, hoses, gauges and torch, plus the first year's bottle rental. Incidentally, be wary of cheaper kits which use non-refillable fuel-gas bottles ('Mapps' gas or similar). Replacements prove expensive in the long run, and the tiny bottle inevitably runs out right in the middle of a job. The genuine kits accept BOC Portapack bottles - BOC enjoys a virtual monopoly on gas supplies at this end of the market. Their only real competitor, Air Products, isn't properly geared up for the DIY user and has far fewer outlets. BOC charge an annual rental of just under £50 for the Portapack bottles, with a gas refill charge of around £25 the pair. There's a German company now offering the same size gas bottles on outright sale in this country. The initial purchase price corresponds to the cost of three years' rental so it wouldn't take long to recover, but getting them refilled might prove awkward - arrangements haven't yet been finalised apparently.
It goes without saying that safety is paramount when dealing with explosive gases. The correct lighting-up and shut-down procedures must be followed, and a fire-extinguisher should be at hand. BOC issue various safety leaflets and they've sponsored a "Video Skill Guide on Gas Welding" aimed specifically at the hobby user. Classic enthusiasts who are thinking about buying welding gear would be well advised to join an Adult Education night class on the subject. As well as being taught the relevant skills, proper safety procedures will be covered, and there's also the chance to try out various types of equipment before taking the plunge and buying your own.
It may be that MIG welding turns out to be right up your street - but just remember that you can't warm your hands with a MIG!
David Landers
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