& here is what I said....
Sir, I didn’t realise you hadn’t previously used
your MIG welding machine to produce satisfactory welds.
I am a skilled welder & have got some bad habits, such
as ‘making do’ with the wire size that I have in my wire feed unit at any particular time, rather than change
to ‘the perfect set up’ for every single job or bodywork situation.
I personally prefer to use 0.6 dia solid wire on car bodywork
for the following reasons:
Rust & paint is always cleaned off the surface first, without
‘thinning’ the steel, (I don’t use grinding discs!) but it does not
always leave perfect pit free steel, & the ‘weld energy’ using 0.6mm wire suits my weld quality requirements perfectly as regards penetration & weld bead profile.
Especially suitable on thin 0.8mm thick panels!
When I come across a very thin part of a panel, or panel edge,
& accidentally cause a ‘burn through’, I am able to very quickly
use ‘back step’ or ‘stitch up’ techniques & procedures to immediately
repair the damage or hole, & continue welding without having to stop or have another ‘repair procedure’ put
into action in order to complete the weld.
This is not always easy while using 0.8mm wire, as obviously
you are welding at slightly higher amperages & the very edge of a hole may not be quite so tolerant to 50amps as it is
There is nothing worse than blowing a hole near a panel edge or ‘thin bit’ & then
having to mess about stitching it back together to fill the hole, & ending up with an unsightly lump of weld metal to
‘dress back’ to ‘acceptable appearance’, as I have professional standards that I do not
'Chasing’ a hole for an inch or so, is just not on.
However, for the purpose of your sanity & patience, &
mine, & considering your capabilities, I think you may be better learning MIG welding by starting
on heavier 0.8mm solid mig wire & then move down to 0.6mm when you feel more confident.
All the car bodywork that I encounter is usually attached to
an ‘older’ vehicle that needs major panel work replacement & repair, but this doesn’t
mean that 0.8mm wire can’t be used.
We are talking about what’s known as ‘short
circuit weld transfer’ here, primarily because as the solid MIG wire hits the weld pool, it ‘short circuits’
the electric welding circuit that you are
creating between your welding power source
(open circuit until the MIG torch trigger is pressed) & the weld pool
on the job you are welding.
As the short circuit occurs, the wire melts
back to create an open circuit, & a droplet of molten wire is propelled into the weld pool via the ‘weld
plasma’, (across the arc) but considering that the wire is continuously fed, this is obviously a ‘forced situation’ & the process is repeated many times per second (up to 60
in this example).
So in reality, when you press the torch trigger & start
to weld, you are depositing a fast ‘stream’ of weld droplets & the ‘crackle’
that you are hearing is the electric arc transition from open circuit to short circuit.
Right Trevor lets get started on the
On new or old 0.8mm thick regular panels, select about 55amps
to start with, this is far too high for a ‘but weld’, but fine for a close fitting ‘spot
weld’ or ‘tight plug weld & even a vertical down ‘close fit lap weld’.
You have to start somewhere with amp settings,
so I always go too high, try a run & I nearly always have to trim down the amps to suit the wire feed
I normally select the wire feed speed at various
‘known settings’ on my different MIG welding machines, but this is actually around 95
inches per minute (ipm).
(But more usually I will set the wire feed
speed at 80ipm & work from there, adjusting the amps up or down to suit the wire, as I know my
machine parameters pretty well)
I can hear you saying that your MIG welding machine has no
readable settings outputs, just dials & switches!
Don’t worry Trev, my machines don’t have digital
panel meters either, as I will not pay for fancy ‘bells & whistles’ unless vital for a specific application!
So, to recap on the ‘start-up’ settings
for 0.8mm wire, set your machine to supply 55amps of welding power. (suitable for thin 0.8 panels)
Turn your wire feed speed control so that you will get far
too much wire delivered when you press the trigger!
Ensure that your ‘argon mix’ shielding gas has
purged through your machine & MIG torch & that the delivery pressure is set to at least 10ltmin,
& that you have no draughts at your ‘practice joint’.
If your Argon gauge is not selectable for delivery pressure,
you only need to know that gas is actually coming out of the welding torch bezel sufficiently to exclude
atmosphere from the weld area (specifically the ‘weld pool’), you are not looking for masses of gas like an airline
blowing up a tyre!
Find some scrap steel that is at
least 3mm thick, that’s right 3mm thick. (call it your practice plate)
Grind a clean line down the 3mm practice plate/angle
iron/whatever, & do a quick short weld run in the flat position.
Did the wire just fly out of the MIG torch & glow red instead
Good, now just reduce the wire feed
speed by a TINY amount & do another test weld.
Same result again?
Good, reduce the wire feed speed
Do another test weld & analyse the result.
Reduce the wire feed speed again by a TINY
Do another test weld on your practice plate
& analyse the result.
You are always looking to produce a satisfactory weld at a
set amperage to suit a given wire diameter & steel thickness.
What you are doing here is starting
at a known (previously defined & proven) good amperage for 0.8mm wire &
0.8 thick steel sheet (55amps), & now you are doing test welds to ascertain if the wire feed speed is
too fast, or too slow. (always start too high & trim down).
So, keep trimming the wire feed speed down
until you can produce a good clean weld with out the weld bead being too pronounced (overly heavy weld metal deposition).
It is without doubt that you will find the
point where you have the perfect wire feed speed at this amperage, & because you are using
a 3mm thick ‘practice plate’ you will not have a line of ‘burn holes’ to look at, as you would ‘practicing’
on 0.8mm thin sheet!
You will also now recognise the sound of the
sharp, crisp, weld crackle noise, as this is a good indicator that you have arrived at the optimum short circuit setting at your selected amps.
You are now ready to transfer your
‘practice plate’ settings to the same material as the job that you want to weld up.
But, patience must persevere, so it is still practice time
for the moment!
Now do the exact same procedure on thinner
Don’t change the amps yet!
Try a quick ‘flat position weld run’ on a bit of
new panel work (or scrap/offcut sheet) that has another bit of sheet lying flat
on top of it so that you are producing a ‘lap weld’.
(Your ‘panel practice joint’ should be clean of
rust, paint etc & they must be a close fit with no big gaps between them).
Therefore, you should, in this instance, be aiming the arc
at the centre of the joint to start with.
Practice on heavier material first if you have too, but you
must grasp the fundamental elements of starting from known amperage
values, setting wire feed speed too high, then trimming down
the wire feed speed until you find the optimum weld parameters.
It is then much easier to use & apply the weld settings
to any thickness of material, as you literally have a working
example in front of you, & it really is straightforward to make MINOR
adjustments to the wire feed speed first,
to ascertain suitability as regards penetration or deposition etc, BEFORE
you start adjusting the amperage up or down & then restarting the systematic
wire feed speed adjustment.
Incidentally, Trevor, if you do have a voltmeter on your MIG
welder front panel, & I have just explained all this for nothing, please set it to provide 15.5
welding volts, give or take ½ a volt, as the welding volts are essentially controlled
by the wire feed adjustment (just to confuse you further!) & are directly relevant to the amperage you have selected (55)
in order for you to get the optimum weld setting parameters every time!
& while we are on the subject of confusion, when you go
to your welding products supplier to purchase 0.8mm solid mig wire, specify a ER70S-6 grade wire, as the
deoxidisers & silicon are beneficial for old car bodywork & it gives a nice ‘fluid’ weld
puddle, with great weld bead appearance.
The more regular ER70S-3 grade is a tiny bit
cheaper, & is also suitable for all positions, but I personally find that the weld puddle is a bit on the ‘stiff’
side for body work.
Your Argoshield Light (BOC gas trade name) shielding gas is
fine for these wires.
& just to make your MIG welding life a bit easier with
car body work intricacies, nooks, crannies, & internal corners; try this:
Cut the end of your MIG welding torch bezel down so that your
copper contact tip is sticking out past the bezel by about 8mm.
Your solid MIG welding wire should have a ‘stick out’
length of approximately 6mm at the settings you arrived at using all of the above set up procedures for 55amps.
This is sometimes hard to maintain if your machine has ‘burn
back control’ which I don’t think it has, but these manual values are a good guide to use.
Sometimes a beginner will be better with 8-10mm ‘stick
out’ & will rapidly learn to control the optimum parameters that allow fast
& continuous welding without any stoppages, such as ‘birds nesting’ of the wire feed rollers,
which can be caused by various poor settings.
If you have correctly set your weld parameters but are having
continuous ‘burn backs’ which cause your mig wire to become melted onto your copper contact tip, check
these next things first before condemning the settings that you can now expertly & quickly arrive
It is vital that you can test & eliminate causes of problems
systematically & immediately without specialist electrical test gear or otherwise!
Before you even start to swear at your MIG welder, double check
that you didn’t just accidentally bump the wire feed control! (I am guilty of this!)
You can do a quick test weld after each step in order to isolate
any potential problem, but complete all steps to rapidly identify any weakness, especially in the welding
circuit, but not inside your MIG welding machine mains voltage control panels or transformer housing!
These things may look obvious at first glance, but this ‘markthewelder
mig checklist’ solves 99% of welding problems, after first arriving at correct weld parameters.
Immediately after burn back occurs, touch the end of the contact
tip lightly with your angle grinder (if the MIG wire has bonded to the end of the tip),in order to reveal fresh wire &
give the torch a quick rotational twist to see if the wire will release from the tip.
You can do this hundreds of times if required, before the contact
tip becomes unusable, my welder trainees are testimony to this!
If no voluntary wire release, slacken off wire feed roller
tension to allow free movement of mig wire (& leave it slack for the moment).
If no voluntary release, remove tip & replace with a fresh
one, as you will not have burn backs in the future!
(Some welders use 0.8 tips for 0.6 wire & 1.0 tips for
0.8 wire & 1.2 tips for 1.0 wire) (just a tip!)
Moving to the MIG wire feed rollers,
first check that the central wire spool carrier has just enough
pre-set tension to stop the spool from ‘freewheeling’ & allowing the wire to unroll or become displaced.
- Double check that the drive wheel (or wheels if you have a
four roller unit) is the correct way around to suit the wire, as the wire diameter rating is etched onto the opposite side of the roller to the corresponding correct groove. This is so that
the installed drive wheel drives the wire via the inboard most groove, but the diameter rating is visible from the outside
of the machine! (strange but true!)
- Then check that the idler wheel (the plain one with no groove)
is free to turn on its bearing or spindle & has no foreign matter stuck to its working surface (this is often missed).
If your MIG wire leads from the spool & through a nylon
‘leader tube’ via a plastic leader sleeve,
- check that the wire has not worn through the leader sleeve
to the extent that the sleeve has gone thin at the tube end.
This can allow the sleeve to move too far inside the leader
tube & foul the MIG wire or cause the wire to misalign onto the drive roller when drawn from the spool.
- If it is grooved at the tube leader end, cut it back to full
thickness or just reverse it on the wire & re-insert into the leader tube.
If you temporarily re-tension the wire feed rollers, you should
be able to see that the wire is perfectly aligned centrally at the lead in tube (from the spool)
& at the torch leader (normally brass tube or similar).
If you suspect side friction on the wire, or any
other misalignment problem, rectify it now.
(Check of course, that the rollers are correctly assembled
& the wire is in the correct groove properly).
Ok? Now that you have eliminated
problems at the machine end,
- manually feed the MIG wire from the spool, through the feed
rollers & up through the torch liner & through the contact tip.
- If it went no problem, great.
- If the wire would not pass from the torch liner into the contact
tip, ascertain that you have cut a ‘reasonable’ end on the mig wire by pulling the wire back out of the torch
using the spool & trying a new tip over the end of the wire.
- If the tip fails to fit, fix the problem now.
If the wire fits through the tip, but fails to pass from the
torch liner into the contact tip,
- remove the liner from
the torch & examine the cut end of the liner (all good torches are user serviceable).
The torch liner is made from plastic coated coiled spring steel,
much the same as an old type ‘net curtain’ wire.
The ends are difficult to cut perfectly square, & this
is what normally causes the wire to misalign at the contact tip, or be cut so that the wire struggles to pass through centrally.
& yes they leave the factory like this!
Now that your MIG wire has an optimum feed path,
This ‘liner adjustment’ also applies to Teflon
coated liners, & is especially beneficial to users of aluminium MIG wire, as the tiniest
bit of ‘wayward end barb’ on the liner can ‘scratch into’ the aluminium wire & cause endless
An easy way to check for a suspect cause of
the liner end problem, without dismantling, is to disconnect the ground clamp welding circuit cable, press
the torch trigger & bend the torch backwards, sideways etc as the wire is feeding through. If a foul up occurs all by
its self, you have just found yet another cause of wire feeding problem.
A visual way is to remove the contact tip, feed the wire through & look for evidence of scratching on the wire, this does not
apply to mild steel solid wires, but flux cored MIG wire driven by really sharp grooved drive rolls suffers from easy foul
ups, as the small nicks from the ‘wheel footprint’ on this tubular wire are
just asking to be snagged! (Especially if the drive rolls are not set spot on)
Now that the MIG wire feeds through everything feely, it is
time to restrict it by tensioning the feed rollers correctly.
I have read about, seen, tried & tested lots of variations
with all kinds of MIG welding wires, & here’s what works with solid wire:
Assemble feed rolls & back off tension,
feed enough wire through the contact tip so that you are able
to grip the wire with pliers or similar.
Increase tension on the drive rolls
until you are not able to easily pull the wire through the torch.
It is as simple as that, in my opinion.
You are aiming to have the wire tensioned between the rollers
enough so that it cannot slip if it meets slight resistance, & you will soon realise the complexities
of that statement should you be unfortunate enough to have burn backs, birds nests or other wire feed calamities that I will
endeavour to help you avoid in the first place!
This gets a bit more complex when using tubular flux cored
wires running through four wheel drive serrated drive wheel systems, but in the main I never have high tension
applied, as crushed wire is a definite situation to avoid at all costs.
& if you apply the same principles to aluminium MIG welding
wire, you will not have any wire feeder problems.
I should have mentioned this earlier,...
but while messing about with spools of MIG wire, you will find that a small pair of Vise Grips (the kind made in the USA)
are absolutely essential to prevent your MIG wire from defiantly escaping from the reel, due to the effects of the way it
is coiled onto the spool.
Always clamp the grips onto a loose wire end
to save a major disaster.
You will only accidentally create a mig wire 'birds nest' once,
& you will remember the Vise Grips forever!
Cutting back the wire that you have damaged with the grips
is not half as bad as rewinding or untangling a big wire spool!
& while on the subject of dodgy MIG wire, avoid ‘cheapest
brands’ that have no manufacturer’s production labels!
Yes, I have tried them out of curiosity, No, I will never
use them again! Period.
Further to MIG wire quality, it is actually made to very stringent
Apart from the complex chemical compositions,
that I will mention later, the wire auto unwinds due to the ‘cast’ properties, which is the diameter
of the wire after cutting a length of 3 metres & placing it on a flat surface, then measuring the diameter
of it as it rests freely on the floor.
Try this yourself, & you will also see that a part of the
coil will be raised off the floor by approximately 24mm at the highest point, & this is called
the ‘helix’ properties of MIG welding wire.
For example; 1.0mm wire
should have a minimum ‘cast’ diameter of about 370mm.
While these references may seem non relevant
to a MIG welder, I have seen cheap MIG wire cause all sorts of welding problems, as the wire exits the contact tip but does
not feed perfectly straight into the weld pool.
Again, strange but true, & covered in depth by AWS
Purely for your benefit, this is mostly noticeable when using
oversize contact tips & training MIG welders to produce heavy spray transfer welds on precision
butts etc, but you wouldn’t be using oversize tips in the first place, would you?
just check that the MIG wire drive feed rolls are tensioned
spot on, & you should be in business with pretty much all bases covered.
There are lots of other technicalities that are very worthy
of mention for your continued MIG welding success, but I will wait until you get going before
preaching any more topics!
Should you have any further questions, please just ask.
PS any feedback or comments is always welcome, negative positive
my desk is manned every evening