Machine Marts Buyer's Guide To Welding
There are several methods for joining two pieces of metal together, but welding offers one of the strongest and most permanent. To weld two pieces of metal the edges of both must be melted, additional molten material introduced and then they are allowed to cool together as one. Obviously very high temperatures are required to melt the steel.
Traditionally, for mild steel, this has been achieved using an Oxy-Acetylene (Gas) welding torch or an electric arc to melt the metals to be joined. However gas welding has the drawbacks associated with storing and handling large cylinders of flammable gases.
Arc welding can be a tricky art to master, moving the welding rod or stick along the weld at the correct speed, whilst feeding it in towards the work piece as the rod melts, but being careful not to touch the rod on the metal and cause the arc to cease! Despite all this there are many people who have the necessary skill and use this method of welding for agricultural repair and maintenance and similar applications. The welding current (amps) available governs the thickness of metal which may be welded.
Machine Mart sells two types of arc welding machine.
Both these types of welder use a 'Stick' or 'Rod' to supply the additional filler metal to the weld. These are coated with a flux compound to prevent oxidation of the base and filler metals.
The AC (Alternating Current) machines, start with the entry level 'Easy-Arc' range with machines providing from 40 to 185 amps. This makes these the ideal choice for the DIY'er or home enthusiast. And the Turbo Arc Industrial range, which, as the name suggests, are designed with the professional automotive and maintenance user in mind. These machines cover the range of 40 to 400 amps.
The second type of Arc welder available from Machine Mart is the Arc/Tig welder. This uses newer 'Inverter' technology to convert the mains AC current to DC (Direct Current) making this an easier to use type of welder. These machines are also smaller and lighter than the AC models.
A more recent innovation in the world of welding is the easy to use MIG welder. Machine Mart has a wide range of these machines to suit the occasional amateur user, the busy enthusiast and right through to the professional automotive and industrial welder.
MIG welders use an envelope of inert gas to protect the base and filler materials from oxidization during the welding process. The filler material comes in the form of a thin wire which is fed at a constant rate into the weld. The wire feed rate and current ampage are both varied to suit the thickness of the metal being welded.
For basic DIY work where the machine will not be used for long periods or required to weld particularly thick material Machine Mart sells the Clarke Weld MIG range which cover from 24 to 100 amps. The Clarke Weld MIG Turbo range machines have the advantage of a cooling fan, allowing longer periods of continuous use making these machines suitable for the professional user. These machines cover from 30 to 400 amps. With the addition of appropriate wire and gas most of these welders may also be used to weld Aluminium or Stainless Steel.
Machine Mart also sells the Clarke Weld dual purpose range, which can be used without gas; by using a flux cored welding wire. The majority of these machines can also be converted to use gas.
For situations where there is no electrical supply, Machine Mart also sells Welding Generators for the industrial user.
The following table is an approximate guide to the size of machine required to weld various thicknesses of mild steel.
Health & Safety When Welding
Safety in the workshop should always be a priority. Of course your own is important, but welding can also affect visitors and other workers around you.
Electric welding produces an arc which is much brighter then the flame used in gas welding and also generates large quantities of both UVa and UVb radiation.
Care should be taken to ensure that no one looks directly at the arc without suitable eye protection. The helmet type head shields offer the best protection as they not only have the correct darkened glass welding lens and protect your face from the UV rays, thereby preventing an embarrassing sunburn type rash. Radiation may also be reflected by white walls, for example. Welding head shields should conform to BS 679, the lenses are graded indicating their darkness
8 or 9
up to 100a
10 or 11
100a to 300a
12,13 or 14
It is also important to protect the rest of your skin not only from the UV, but also from splatters of molten metal. Overalls should be fire retardant and gloves and footwear made from leather offer the best protection.
Rings and other metallic jewellery should not be worn at these are a capable of creating an arc with the welder.
Your work area should be kept clear and you should avoid trailing cables across the floor, where possible.
The floor should also be dry- you are using high current electricity! For that matter, avoid touching the electrode too!
You shouldn't weld near gas bottles, high pressure air lines or flammable materials and remember to allow time between cleaning the work piece and welding it, if you have used a flammable cleaner.
There should be good ventilation, to remove the fumes created when welding.
If welding is being carried out on electrical equipment, it should be turned off and disconnected to avoid damage.
Welders up to 130a may be connected it the mains with the 13a, 3 pin domestic plug supplied, larger machines should be connected using the appropriate industrial connector. You should always ensure that your electrical supply is adequate.