Many people with off road vehicles consider other work on their vehicles which is over and above the basic servicing and maintenance, this is usually a variety of modifications which involves fabrication works. Fabricating requires a lot of expensive equipment, which is often purchased over a longer period of a person’s life, in this section we will look at this equipment and determine the most suitable equipment for our hobby. We will decipher some of the technical jargon and some of the misconceptions which are prevalent, and hopefully allow people to make an informed decision when purchasing expensive equipment and not purchase based on advertising myths.
Welding is the mainstay of metal fabrication, it is an old technology which has advanced in recent years with the advent of modern and reliable electronics, and this has translated into reliable and cheaper welding equipment for the home fabricator.
The oldest form of welding was forge welding, blacksmiths traditionally heated metal until it was molten and hammered it together to form one solid unit, this was superseded by gas welding, and gas welding gave more control over the heated area for welding. Arc welding superseded gas welding, this is basically a controlled short circuit of electricity passed through a metal rod, originally these were plain metal and required considerable skill to master, this form of welding remains today, and the rods or electrodes come in numerous types and sizes for most applications. MIG or metal inert gas welding is the most recent upgrade of a technology called wire welding, wire welding used to be done with controlled machines dispensing a flux powder onto the work piece and following it with a continuous wire feed. Wire welding could originally only follow straight lines, but was good for larger straight lines of structural or heavy equipment, MIG allows the user to follow any contour, using the same principles.
TIG or tungsten inert gas welding is more specialised, this basically uses electricity to form an arc and filler rods are fed in by hand, basically it is gas welding with the arc produced from electricity; so a combination of two technologies to good effect.
Welding uses a simple principle, that is to melt metals into a molten state and introduce a filler, that may be an electrode with stick welding, or wire with MIG welding; both form or use a shield to produce a gas around the weld to exclude oxygen. If oxygen is allowed into the molten pool it allows porosity and forms a poor weld which is weak, stick welders do this by having a flux coating on the electrode, this cleans the weld as it is molten, and this rubbish forms on the surface of the solidified weld as a slag. This slag is removed by chipping it with a chipping hammer.
MIG welding uses an external shielding gas which comes from the gun, it surrounds the welding wire to form an oxygen free zone around the molten pool, many gases can be used for differing materials, but for our purposes we will concentrate on steels.
For 240 volt applications we need to look at the electrical supply, this is usually a 30 amp for higher welding outputs needed by us, this may mean an additional electrical supply suitably rated is needed, always check the machine ratings before purchasing. This often precludes the use of a moderately powerful machine from a domestic three pin plug and normal extension cables as these will overheat with the power demanded by our selected welding plant.
Stick welding uses a copper wound or basic transformer, this transforms electricity to a lower voltage, but increases the amperage, it is this amperage which we use as a measurement, the most powerful stick welders will supply around 150 amps of welding power from a 240 volt, 30 amp supply. These are limited to the same supply frequency as the electrical supply, in most countries this is 50-60 hertz; the larger the amperage output the larger electrodes it will handle; these machines provide an AC (alternating current) output. Electrodes are available in standard sizes, these are 1.6mm, 2mm, 2.5mm, 3.2mm and 4mm; this is about the maximum sized rod you could weld with from a domestic electrical supply, using the largest machine you could use. Some machines produce more, but some are dual voltage using single phase 240 volts, others are single and three phase which can weld up to a current on single phase, then you have to switch to three phase 415 volts to obtain the machines higher power output. Some machines can produce up to a claimed 170-190 amps from single phase, look at the duty cycle and you will see these are very low, a number are only domestic use only and do not incorporate the cooling fans for longer operations, or thermal overloads to protect the transformer.
More modern inverter stick welders or inverters are becoming cheaply available, these use DC (direct current) for welding, they are often slightly down on power output compared to ordinary copper wound transformer machines, but DC allows this. AC welding produces a wide fluctuation in power output, this means if the machine is set for 100 amps the output may fluctuate from 80-120 amps, with a DC machine this fluctuation is halved, allowing a more consistent and higher actual welding usable output.
Duty cycle is something confusing to many people, duty cycle gives the maximum welding current the machine can provide if it is welding for 60% of the time; you will find many disparities between different welder manufacturer’s machines here. Duty cycles for welding machines are mainly quoted at 60% duty, but may vary from manufacturer to manufacturer, and from machine to machine.
Comparing two welders currently in production, we see they both provide 200 maximum amps of welding power, but their duty cycle of 60% shows one will provide 102 amps, the other will provide 156 amps. This means the lower rated machine will not weld anywhere as long with as high a power output, so always check and compare the duty cycle when looking for welding machines of any type.
Stick welders are very simple, apart from the transformer they have two leads, the positive and earth, the earth is connected to the piece to be welded; the positive has an electrode holder, electrodes are placed into this and the power is set, you then weld.
Basic stick welders contain very little more than this, but they are reasonably cheap; this is usually because the fittings are cheap, I would always advocate replacing the cables with larger and longer items, the electrode holder with an industrial type, and the earth clamp with an industrial type.
Always aim for an industrial or light industrial type welder, these are fan cooled which gives longer welding times and a higher duty cycle, this means higher outputs for welding heavier items around the home. Many machines come with a thermal trip, always look for this as it switches the welding current off if the transformer becomes too hot, this saves the machine and gives it a long life, my 140 amp stick machine is over 20 years old and still going strong.
Look for a rating of around 140 amps or higher from a single phase supply, this allows larger 3.2mm or even 4mm rods to be used with these machines, this is great for heavier general home fabrication work, or chassis work.
Inverter powered machines are now common and available cheaply, they cost more than an ordinary transformer based stick welder, they can often be multi use welders as many; with a conversion kit, can be converted to run as stick or TIG welders. Inverters are DC welder’s, they are very light when compared to transformer based welders as it is the transformer which contains the weight. Their downfall is the striking of the initial arc, many come with a facility called hot start and any potential purchaser should choose a machine with the hot start facility, most come with a cooling fan and overload protection, an essential.
Inverters are generally sold without accessories for either stick or TIG welding as they are only the power source, this may mean buying the inverter and then the accessories for your preferred welding application.
Where the inverter is used for stick welding all that is needed is the leads and a head screen, for DC TIG welding a TIG kit is required, this comprises an umbilical which contains a gun with the tungsten tips, gas shield, and a suitable supply of shielding gas. Many kits contain a regulator for the disposable gas bottles, using these is expensive as they are small and contain small quantities of gas, they work at much lower pressures than the industrial bottles, so are only suitable for smaller welding jobs.
Stick welding has advantages and disadvantages, these are:
Stick welding has limited uses for automotive work as they cannot be used on very thin metal bodywork or sheet steel, even experienced welders with many years of experience struggle.
Stick welding does not require the metal to be spotlessly clean, it will cope with a small degree of dirt and rust as the rods flux coating cleans the metal.
Stick welding is the most flexible and cheapest form of welding, just fit the right electrode and you can weld a variety of items as well as mild steel; stainless, and even aluminium can be welded with the correct machine and rods.
Stick welding leads can be infinitely long, this means extensions can be made and connected together with suitable plugs to allow you to work away from the welding transformer, great if it is raining, freezing, or snow is on the ground. Leads must be of a greater size or diameter if longer ones are used or you will experience power losses on longer runs.
Consumables are available almost anywhere, they have so few wearing parts that they are very reliable.
Inverter based units have very precise current control due to their electronics.
Buying a Machine
Always go for the best make and model you can afford, ensure it has stepless power adjustment to allow you to tailor your power output, ensure it is a light industrial model for longer operating times, and is fitted with a cooling fan.
Check the power output at 60% duty cycle to ensure you can have the required power output for larger fabrication work; and ensure it is fitted with a thermal overload facility to protect the machine when welding with larger rods.
Where an inverter is purchased, ensure it has the hot start facility for stick welding, and high frequency start facilities for TIG welding.
MIG welding has become popular in recent years due to its wholesale introduction into the general fabrication and repair industries, MIG has many advantages over traditional stick welding, this is generally its ability to weld very thin materials.
MIG welding has a DC transformer unit, a separate gas bottle for the shielding gas, and an umbilical which connects the transformer to the welding gun, it contains a spool of wire which can be of various standard weights and sizes.
Some MIG welders omit the gas bottle in favour of a flux cored wire, avoid these as they are dangerous as they emit boron and other toxic gases, which can kill if inhaled; these are already banned in many countries, and for use in industrial applications in the UK. Boron was the base of many gases used by the Nazi’s in World War One before mustard gas, and used in the concentration camps in World War Two; so we know its ability to kill.
MIG welding operates by using a continual spool of wire which is available in two common sizes for our applications, these are 0.6mm and 0.8 mm diameter, other sizes are available for the larger industrial machines used in fabrication shops. MIG welders have the wire fitted to a spool inside the transformer unit, this is fed through either two or four rollers, from here it enters the umbilical and runs inside a liner, it exits the gun through a contact tip which provides the power to the wire. The gas bottle provides the gas to the gun through a small diameter tube, when the trigger is pressed it opens the gas valve inside the machine to let the shielding gas through, at the gun it exits through a nozzle and the shroud controls its direction around the welding wire. As the trigger is pressed it also powers the two or four feed rollers to start the wire feed at the same time as the gas is fed through. MIG wire comes in different spool sizes, these are hobby (0.7Kg), 5Kg and 15Kg, select a machine which takes a 15Kg spool if it is within your budget, these larger spools work out much cheaper to purchase than three 5Kg spools, or 21 0.7Kg spools, as the 15Kg spool is the industry standard size.
MIG welding has several advantages over stick welding, this is its ability to weld the thinnest sheet metals, thinner than those found on car bodywork, it has less distortion on the thinner metals than stick welding due to using a shielding gases. MIG welding is the easiest form of welding to learn for a beginner, those of us old enough to remember moving from stick welding to MIG were surprised just how easy it was. MIG welding has one major downside that is the metal preparation, unlike stick welding MIG likes the metal to be scrupulously clean, this means time in preparing your weld area prior to welding to ensure cleanliness for perfect welds.
MIG welders come in many forms, and with an array of features, there are the hobby machines which are smaller in power output, and the more commercial automotive and light industrial machines. Avoid the hobby machines, they are always working flat out when welding heavier metals, and are limited to about 3mm plate thicknesses, aim for the 170-220 amp range automotive type machines as their power output and duty cycle is much better than the hobby machines.
Industrial machines at 170 amps will weld metal thicknesses of around 5mm, 220 amp machines will weld material thicknesses of around 10mm thick, so offer a much better welding thickness range than stick welders, so one machine for vehicles and general fabrication.
Hobby machines tend to come with integral umbilical, this means you are tied to the manufacturer for consumable items such as the liner and contact tips required, as these are consumable items; these tend to be expensive. Industrial machines generally have the Euro connector, this simply plugs into the front of the machine and has a screw collar to hold it in place, always go for a model with a Euro connector, and this means sourcing liners and contact tips is much easier and cheaper. Many varieties of consumables are available for the standard Euro connector, liners with PTFE or Teflon coatings, and contact tips can be bulk purchased cheaply, if you know a welder working for a fabrication company, they may recycle a few for you (theft is illegal).
Umbilicals with Euro connectors come in a range of lengths, these can be up to 8 metres long, the normal size is around 4 metres, this is ideal for general welding as it allows the transformer to remain static, hobby machines have much shorter umbilicals. This often means stopping and moving them and their gas bottle while working.
MIG welders come with a basic power setting knob, this may be push buttons or a multi-position rotary switch; this gives the power settings, aim for a machine with as many as possible, in addition some may have a fine power setting switch, this fine tunes the power. MIG’s also have a rotary switch to control the wire speed, again it might be one, or two switches; many machines have auto adjustment of wire speed, depending upon the power selected, some have auto wire speed settings with a fine wire speed control.
It is down to personal choice which option to select, for a beginner I would suggest auto wire speed settings with the fine wire speed control, this gives an approximate wire speed setting for the power selected, basically the wire speed is near where it needs to be.
Other features may include a spot welding timer, this is basically an on/off switch with graduations along it, which when turned on will allow the weld time to be set, it will then cut off when the set time has elapsed, even though you still have the trigger pressed. This is advantageous where repetitive spot or stitch welds are required when fitting panels on sheet steel; or where consistent stitch welds are required on heavier fabrications. Spot weld timers usually operate within the 0.5 – 10 second ranges, but may vary depending upon model or manufacturer.
Gases And Gas Bottles
If you use a MIG or TIG welder you will need a gas supply, this comes in the form of bottles which connect to the rear of the welding machine, this provides the shielding gas to prevent porosity and cool the area around the weld. Bottles come in two main types, these being the disposable bottles and refillable bottles, disposables are extremely expensive, refillable bottles are the industrial type which are commonly seen; avoid the disposable type. If you want a refillable bottle you will need to set up an account with a supplier, the big names are BOC, and Air Products in the UK; but many others also do welding gases. Setting up an account is expensive as they charge an annual fee and then charge for each refill of your bottle.
Many people obtain an empty bottle and have it swapped for a full bottle at local companies or scrap yards, many make a small profit on these transactions, but you will have to find such a supplier who supplies gas from the same manufacturer as your bottle.
Gases for different metals vary, for basic MIG welding on mild steel you can use carbon dioxide, this gives a suitable gas shield to prevent air entering the weld, and some cooling effect for the work piece. Many other sources of carbon dioxide are available, these are pub bottles for pressurising beer and carbon dioxide fire extinguishers, many refillers of fire extinguishers will refill your fire extinguisher cheaply.
Argon/carbon dioxide mixes are available, these are the most commonly used in industry as the introduction of argon increases the temperature of the weld pool for a given power output, they also cool better, and offer better cleaning properties over carbon dioxide. These mixes are called Argoshield and come with 5%, 10%, 15%, 20% or 25% argon mixed with the carbon dioxide; Argoshield 5 or 10 are fine for home welding applications, the number refers to the argon percentage in the CO2.
With any industrial bottle you will need a regulator to control the high pressures in these bottles, this reduces this to a pressure suitable for your welder, this pressure is adjustable; they come as single or two stage regulators, always go for a two stage regulator. These give a more controlled output and having adjustable pressure output means the pressure can be tailored to your machine to save excess pressures being used, and wasting gas.
Do not confuse the often supplied regulator which comes with the machine for one which fits industrial bottles, these supplied regulators are normally only for the disposable bottles, have different fittings, and cannot handle industrial bottle pressures. Do not be tempted to modify them to fit industrial bottles as they will simply explode the first time you switch on your bottle.
Many machines come rigged for the disposable bottles, if you switch to an industrial bottle you will need an adaptor to adapt the small bore gas inlet pipe to the larger bore industrial pipe, adaptor pipes are available cheaply so buy one of these.
Where fire extinguishers or pub bottles are used, special adaptors are required to adapt them to a two stage regulator as they have different fittings, again these are commercially available.
Which ever type of machine you select, you will require a number of additional items; welding produces radiation which is similar to extreme sunlight, this can easily blind you without protection; welding produces great heat as well.
Welding masks are vital, they protect your eyes and face from the emissions, they come in three main types, these are hand held, head screens, and automatic reacting screens.
Hand held screens are the basic type, you simply hold them in front of your face when welding, they allow you to see through the welding filter which is tinted.
Head screens sit on your head, much like a safety helmet; these are hinged to allow them to be lifted when you are not welding and are more flexible as they allow you to have a hand free for holding items in place while tacking or welding.
Both these sorts have a tinted lens or filter, these are available in a range of shades from 9 to 14, these are replaceable and usually have a protecting clear lens placed in front of them, 9 is the lighter shade, 14 the darker shade. Lighter shades are used for smaller power outputs as their light is not as intense as those produced by higher powered machines.
Auto darkening screens are actually head shields which sit on your head, unlike the other two they do not have a fixed value filter; this is very light when not welding and darkens as soon as you begin welding, they are usually adjustable from 9 shade to 14 shade. Auto darkening welding screens are the one to have if costs permit, they allow you to see your weld area and line your torch or rod up before welding, and you just continue, they darken as the arc is struck, to the shade set, and allow you to have a spare hand free.
Welding gauntlets are basically long leather gloves, these allow heat to travel through them, but very slowly so you have time to remove them if you are handling hot metal, and they protect your skin from radiation burns and burns from spatter or molten metal droplets.
As with welding screens they are essential kit.
Overalls are another essential item, these must be cotton only, they must not be many of the man made materials commonly found today as these cannot deflect the molten metal and this simply burns through them. Cotton might ignite if it is plain cotton, but it will only smoulder, one other variant of these are available, these are Proban overalls; Proban are cotton overalls dipped in ammonia which gives them protection from burning or smouldering.
Welding boots are an advantage, these are long enough to come up your legs, your overalls cover them to stop any hot metal going down your boots; in reality and long leather boot will suffice as long as the soles will stand the heat of molten metal.
Consideration needs to be given to the welding area, along with the type of welding you intend to do, if this is on vehicles consideration needs to be given to additional items not listed in the MIG welder’s handbook. Always follow the safety instructions in the welder’s handbook, also consider vehicles have fuel tanks and fuel lines, they are also under sealed and have other flammable coatings to protect them. One of the most prolific causes of fire is previous owners coating the insides of box sections such as inside sills or chassis rails with a variety of coatings such as Waxoyl or Dinitrol, this is very flammable so be aware of these possibilities.
Take the appropriate measures with fire extinguishers and water