I have noticed that questions coming from the new blokes to this Metal work forum section of the board where relative to Mig welders. In most cases our motivation as the struggling home owner DIYER it’s about saving a quid.
Mig welders have their place fellas, but really for a lower cost and versatility you can’t beat a MMAW electrode machine. It doesn’t take a rocket scientist to learn to use the process. If I could learn it any one could.
For those who are new to the use of the humble stick welder, I thought I would offer a few helpful hints to those new “would be “carpenters in steel.
Designing and Selection of material
Flat bar, angle section steel, sections of round, square and rectangular tube are the most popular steel types. The thing to remember is to design with the particular welding process in mind. If you design too lightly you may end up burning through the thinner material. Try to limit your thinnest section to 3mm or better. It is also wise to consider the joint configuration. Tee joints are preferable where you can weld a fillet. If you must have a butt edge joint consider a bevel on one or two of the edges. Amateur welders have a habit of welding a bead on top of a butt joint and if its not too pretty, end up grinding it off flush with the surface. The result a micro thin depth of weld that fails eventually....
Selecting the correct electrode and adjusting machine amperage.
Big time amateur stuff ups emanate from a failure to use the correct electrode and or setting the amps correctly. When I was a 1 st year apprentice my boss taught me this way
Backwards SAVAGE. No he was not upset at me .It was all about this
E- Select the correct grade of ELECTRODE for the work- For us if it’s branded 4112 its ok for mild steel (for the Americans its 6013)
G- GAUGE – the old fart way of identifying electrode wire diameter – To us it’s in metric 2mm, 2.6mm 3.2mm.Most home welders use 2.6 and 3.2 mm
A- AMPERAGE setting for the diameter electrode you have chosen in the above
2 mm = 70 to 90 amps, 2.6mm = 90 to 100 amps, 3.2 mm 110 to 130 amps
Note these settings are approx only because of variables such as household input voltage- its not always 240volts and can vary down as much as 10% down, your house wiring and YOU. Yes, you can vary the input
(slightly) as you weld. - more shortly
V- VOLTAGE – The heat input into the welded material which causes the bead to flatten. Hold the arc too far off the job and the voltage increases. The trick is the hold arc closer and you will automatically increase the amps – Also affected by poor connection to the work - Keep it clean of rust and dirt and spatter.
A- ANGLE – Lateral (Side) angle and Drag angle. Side angle is variable and related to the joint position as required. Drag angle – No more than 10 to 15 degrees off 90. Too much drag angle = too little arc penetration.
S- SPEED of travel. Look at the ripple pattern of your welded bead. If normal its about the curve of your finger nail, sort of crescent shaped. Too fast and its shapes like and arrow formation. Too slow and ripples are very slightly round almost flat.
Before you weld
I will assume you know how to set your helmet from previous posts. It is best to make a test run on piece of scrap of the same type and thickness you are going to weld on. It is better to have to ditch a piece of scrap, than the job you taken hours to prepare, if you have mis set the welder adjustments.
Check your earth connection is secure and clean. On some fiddly work I make a little arc strike block to strike on and jump quickly to the start of the weld while the rod end is still red hot....
Tack Welding and Assembly
Irrespective of the section or type of steel that you assemble your welded project from it is essential that the collection of assembled joints are all completely tacked first to minimise any distortion.
A tack is a short length of weld anywhere in length between a dot of weld and 25 mm ( actually they can be longer , but not usually for home construction.) A good rule of thumb is small beads require short length tacks and longer beads need longer tacks..
Select your electrode and then increase the amperage by 10% of the welding amperage that you will use. The purpose behind this is to keep the tack flat and allow deeper penetration. It increases the capability of the tack to bite in and hang on when assembly requires some re direction of components with a BF hammer. Higher amps keep the tack in a flat profile and make easier to weld over the top of the it .Flip down helmets were mentioned in earlier post. The tacking procedure is where they become really essential.
Include an arc striking block quite near to the position where you need to weld. There a two purposes here. One is prepare the end of the electrode for “ arcing “ removing any cracked or spalled rod ends. Number two is to get the electrode end red hot reducing the electrical resistance when red hot, enabling a easy ignition of the arc.
Beginners often make the basic mistake of tacking and welding each joint in sequence. This invariably gives distortion a free rein with disastrous results.
Tacking is a skill which requires practice. Some rules apply
The key is to tack one corner , check it for plumb and /or square and then tack the opposite diagonal corner , thereby locking the joint in alignment.
Having assembled your project and checked it for square . Where possible start the arc at the opposite end to the tack and complete it by welding to the tack. . Avoid starting or finishing a weld on an inside corner, such as would be found on an angle section leg tacked to a frame. Start your bead on an outside leg and weld through and out of the internal corner finishing on the other leg. That way you will minimise slag holes. Set your welder amps adjustment as recommended by the manufacturer.
Make sure you keep your arc length down within a core wire diameter. For those addicted to the well known brand blue coloured electrodes be aware they do not tolerate welding over their own welding slag. In any case clean and brush your tack it reduces the likelihood of inclusions during welding to or over a tack.
Identifying a less than efective welding technique
It might be as well to start at the beginning .
Having trouble in striking your arc. A couple of possible causes are
1.The electrode end broken cracked or chipped. If the electrode end is not covered in flux it won’t strike well.
2. The earth return clamp is not connected securely to the work. It is best attached directly to the work piece. If not all the little balls of spatter on the bench raise the job slightly off the bench surface and decrease the surface electrical contact and therefore lessen the ability of the arc to initiate. Use an arc strike block to strike the electrode and jump straight over to the work , while the electrode end is still red hot. This burns any possible cracked and spalled end off the stick and reduces the starting resistance.
A strike block is simply a block of steel ay 50 x 50 x 10 square. I mount mine on a 10 rod tacked ( tacked-not welded ) to the bench top.Come time when its all built up and unusable – smack it with a BFH and replace it.
