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LEARN TO WELD - PART 1

LEARN TO WELD - PART 1

15th May 2016

How to

Basic weld repair is in the scope of many DIYers. All you need is the right kit and instruction, and the patience to learn and practice the skill, as Alisdair Cusick explains



Welding is probably the most common repair that’s farmed out to a specialist. There’s good reason for that – it’s is a tricky job that needs the correct equipment, skill and experience to do correctly. Getting it wrong could cause more damage than good. Do it badly, and it’ll need doing again a couple of years later. But basic welding can be learned, the equipment is affordable, and with perseverance most of us can become capable of a serviceable weld repair.

Here, we explain the basics to give you a flavour of some typical applications of welding that you can try as your skills and confidence develop. This is not the route to becoming a qualified welder but, if you want to learn more, or supplement your skills, now is the time to enroll on a local evening course. There are plenty at local colleges around the country, running through autumn and winter. You might progress through basic chassis repair to delicate and highly skilled body work, but you’ll at least gain an insight into what is involved in executing the correct repair, and what makes up the garage bill.

WHAT WELDING MEANS

At its most basic, welding is the joining of two pieces of similar metal by melting and fusing them together. It also involves the addition of more material – a welding rod, or filler wire – which melts and fuses into the joint. There is much to get exactly right to ensure the joint is strong and serviceable, and that’s where the skill and correct equipment comes in. Skill comes with practice – we can all learn to play a tune on an old piano, but does anyone want to listen to it until we’ve really practiced and become a competent player?

So it is with welding – don’t expect to buy a very cheap set of equipment, and decide your first experience is the time to weld in a new rear crossmember, a boot floor and the bulkhead outrigger to get the vehicle through an MoT. Instead, spend time on learning and understanding the basics, checking the work, and then build your confidence and skill until your welded joints are as strong as the original metal. There are various welding processes that we can use, but they depend on several factors. These include: the materials being joined (usually mild steel, but also aluminium or even stainless steel), the item and location of the subject (thin bodywork or thick chassis plate,) and also the working location (in a workshop or outdoors). Each has an effect on the choice of welding equipment and  process used and, with the right choice and skill, it is possible to weld anything from 1.2 mm car bodywork to inches-thick steel structures.

The more extreme the situation, the more complex the equipment and skills needed. For vehicle work there are three main welding processes to choose from: Metal Arc welding (also known as stick welding), Metal Inert Gas (MIG), and Tungsten Inert Gas (TIG). There is also Gas Welding, which has its place but, for DIY repairs, there are other simpler and faster methods to learn on.



Metal arc welding
Arc welding uses a rigid steel electrode rod which is encased by a flux coating. The end of the electrode is held a few milimetres from the workpiece. Electrical current passes down the electrode creating the arc as it jumps the gap between the electrode and workpiece, creating enough heat to melt the end of the electrode and the workpiece, fusing the materials together.
The flux outer coating burns off, controlling the oxygen in the weld area, but leaving slag to be chipped off the finished weld. Arc is useful outdoors because, unlike MIG and TIG, there is no shielding gas to be affected by wind. With Land Rover repairs we usually have access to power in a workshop, so arc is only really used for thick chassis work, rather than bodywork.

Metal Inert Gas (MIG)
MIG is the process we’ve probably all got in our heads when we think of DIY welding. It uses a feed of gas to shield the arc, thus keeping airborne contaminants and natural gases away from the weld zone, giving an improved weld quality. The electrode is in the form of a steel wire which is fed into, and melts into, the joint. As you press the torch button, gas and wire is constantly fed as you form the joint. MIG is a quick process to use, though it does create spatter, which can melt into glass or damage bodywork, even ignite combustible materials.

Tungsten Inert Gas (TIG)
TIG shares much in common with MIG, in that both use a gas to shield the weld joint at the arc. Whereas MIG’s wire feed is the electrode, which melts into the joint, TIG uses a fixed tungsten-point electrode that is not consumed. To form the joint, a filler wire is hand-fed into the weld joint. It is a skilled process, but produces a neater weld than Arc or MIG, as there is no spatter, and the heat is almost pin-point in its application, minimising panel distortion. TIG is most often used for welding stainless steel, or very thin aluminium or steel. Its downfall is in being slower and trickier compared to MIG. It’s the choice for aluminium body panels.

Gases for MIG and TIG welding
The purpose of gas is to shield the molten arc from oxygen, nitrogen and hydrogen, which are naturally present in air. This helps prevent porosity in the welded joint, and controls spatter. Commonly MIG and TIG welders usually use a mix of CO2 and argon. Other options include helium and oxygen, and people develop preferences to their own favourites. It is possible to even use just CO2, but that typically causes excess heat and increased spatter over a welding-dedicated CO2/argon mix.

WELDING WITH MIG

Ideally AN aluminium body would need TIG welding, but MIG is most practical for the inner steelwork and chassis, and perhaps TIG for experienced welders. TIG is the neater, more artisan method, but requires the most skill – a case of melting the pieces to be joined using the torch in one hand, while feeding the filler wire in (at the correct speed and place) with the other. Indeed, to start welding, many suggest learning on TIG, then going to MIG, as you’ll then have an appreciation of the process and may, therefore, have fewer issues. MIG is a simpler and faster process, more suited to the home welder.
Get to know your machine by carefully reading the instructions. They will suggest the best amps and wire speed for the thickness of plate you are working with, and the best wire size. The notes will also explain how to feed the wire through to the welding tip and trim off the wire end using side cutters. Position the torch close in, wearing a visor and protective clothing, and press the trigger. The wire will arc, but will also feed out automatically, so you need to move the torch as it does so. In the first instance try a simple tack weld with the torch held in one position – it takes only a second or two. When making a longer run of weld, move the torch along the join at a speed that allows the metal to fuse together. Aim for a smooth profiled weld – it’s just a matter of practice to get the speed and distance correct.
Too slow, and the weld profile will be shallow: too fast, and the profile will be high and narrow. Everything stops if you release the trigger. You’ll eventually get to learn from the sound during welding when it is going right, with a nice, domed, penetrating weld forming. Let’s look over the shoulder of Kingsley Cars’ welder, Steve Fuller, as he demonstrates some simple practice excercises, and some problems you can expect in getting a handle on the basics of MIG welding.



KINGSLEY CARS
Our thanks to Oxfordshire-based Kingsley Cars who have helped with this feature. Kingsley Cars is a respected specialist in Range Rover Classics with a reputation for body-off restorations involving comprehensive weld repairs (currently 16 Classics are being built up). Kingsley’s 15 employees also provide a complete garage service for all Land Rovers, including bespoke conversions.

CONTACT:
Kingsley Cars Ltd, A40 Eynsham By-Pass, Eynsham, Witney, OX29 4EF www.kingsleycars.co.uk  Tel: 01865 884488

 

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A typical gas MIG welder. The gas bottle is at the rear of the unit. The earth strap (top) is secured to clean metal near the area to be welded.

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