Thursday, August 5, 2010


There are four types of welding equipment which the DIY restorer might typically consider. These are Arc (often called 'Stick'), MiG, Gas and Spot welding equipment. Arc welding equipment is comparatively cheap to buy but has severe limitations regarding the thickness of metal it can be successfully used on. If the metal is less than '/.3 in. thick (i.e. all body panels) the fierce arc welder will quickly burn right through the metal which it is supposed to be joining! Arc welders are best suited to use on heavy section agricultural vehicle metal and are useless for the vast majority of car restoration work. An accessory called the Kel Arc Body Welder is available, however, which is claimed to cut the hot amps from the arc welder and to have a stitching motion which lifts the rod on and off the metal, allowing it to cool and preventing the rod from either sticking to or burning through the metal. The author has not had the opportunity to test this equipment. The costs of the Kel Arc attachment and an arc welder will still be slightly under the purchase price of a MiG welder.
The MiG (Metal Inert Gas) welder is the type normally used by the DIY restorer, and by the majority of professionals as well. It surrounds its electrode (in wire form) in an inert gas, so preventing the metal from burning through. It may therefore be used on the thin metal of car body panels. Two types are available. The more traditional MiG welder uses gas from either a small cylinder strapped to the unit or from a larger, remote cylinder, and different gasses are required for welding different metals. The newer type of MiG (the 'gasless' MiG which can only be used on steel) substitutes a substance contained as a core within the wire for the gas. Because large gas cylinders are expensive to buy, hire and fill and because small gas cylinders have to be replaced frequently at relatively high cost, this newer type of welder appears to offer advantages. The main advantage of the gasless MiG is that it possesses only one consumable (the cored wire) to run out ofl The MiG welder is probably the best type for a beginner.
The author uses a SIP 'Handymig' Gasless MiG welder; a unit which proved quite easy to use and which is capable of first-class results. The cored wire needed for a gasless welder is more expensive than that for a gas MiG, although because no gas need be purchased for the former, the running costs of the two will not differ greatly. As already stated, the fact that there is only the one consumable (the cored wire) to run out is very much in the gasless MiGs' favour, although the author has on occasions experienced difficulties in obtaining the specialised cored wire locally, whilst plain MiG wire is widely available. The cored wire is often (the author believes erroneously) referred to as 'flux cored'. It is essential that you are not inadvertently supplied with standard non-cored MiG wire for use with a gasless MiG, because without shielding gas, this will burn through body panels.
Gas welding is arguably the most versatile of all, and can produce excellent results in the hands of a skilled person. Arc, MiG and spot welders all use electricity to heat a very small area, whereas in gas welding a torch is used to heat both metal and welding rod, and a larger area of metal tends to become very hot as a result. The greatest drawback is that the heat which is necessary tends to warp body panels and can easily give a new panel a corrugated finish! Gas welding equipment can also be used for brazing and for heating stubborn nuts and bolts which refuse to move otherwise.
Spot welders are the easiest to use, although they are limited insofar as they can only be used (unless a range of quite expensive special arms are also available) for joining together the edges of two metal 'lips'. For such joins they give an unbeatable combination of ease of use, strength and neatness. No wire nor welding rod is required, because the spot welder uses electricity to heat and fuse two panels together. Few DIY restorers would go to the expense of buying a spot welder because of their limited applications, and most opt to hire them as and when necessary from a DIY store or tool hire business.
When using a spot welder two conditions are necessary for good results. Firstly, the two pieces of steel being joined must be tightly held together. Secondly, the surfaces must be spotlessly clean. It is nowadays normal practice to spray special zinc-based paints onto the metal before performing the weld, in order to reduce the chances of corrosion occurring.
Yet another accessory which has been available for the Arc welder for some time is claimed to allow users to spot weld two sheets of steel with access from one side alone, whereas the spot welder requires that one electrode is placed either side of the join. The Arc welder accessories have not been tested by the author, and while he cannot personally vouch for them he cannot see any reason why they should not work. It would be vital that the panels being joined were firmly clamped together in some way immediately either side of the single electrode, because the top layer would expand more rapidly due to heat than the underlying layer, so that the two would tend to move apart. Still on the subject of Arc welder accessories, kits are available which enable it to be used for brazing. Whilst the author has heard no comment detrimental to any of these Arc welder accessories, he has yet to find an experienced professional restorer who champions them.
Most welding equipment can only produce neat and strong results if the operator possesses the appropriate skills. The quickest way to acquire such skills is to enrol in a short welding course, perhaps an evening class at a college. Whilst it is true to say that you can teach yourself to weld, it is not recommended that you do so (especially using your own car as a guinea pig).
Because the MiG seems to be the type of welding equipment most commonly owned by the DIY restorer, an introduction to its use follows. If you wish to find out more then there are several excellent books available on the subject.

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