First time welding thin sheet metal with gas! Concave tack welds

[dobson156]

Yeah, it just stabs at the metal if it can't conduct straight away.
A flap disc will be much easier to use than a grinding disc, as it'll "spare" more of the steel, as opposed to making it (even) thinner!

All the Best,
CJ

I'd already hit it with a prep disc, but this was to remove the paint not specifically trying to brighten up the metal.

Do you find a flap disc cuts down welds faster than a grinding a normal disk? The welds I did on the car today were pretty ugly and will need a lot of grinding down and it seemed to be taking an age even with a decent Norton grinding disk. I've got some flap discs in a variety of grits, I can try them tomorrow.

 

[dobson156]

There’s not a huge amount of gas coverage, as evidenced by the smoky residue left around the welds, but it’s not so bad that they’re all porous & rough-looking, plus those mini-regs are notoriously stingy with flow, probably mainly so that the gas lasts a tiny bit longer!

The manual suggested 2-3litres per minute. I set it to 3 with the trigger pulled. That said I am working outside so that probably isn't helping, I'll up it to more like 4-6.

Another thing I am probably getting wrong is that whilst I am trying to keep the gun about 1/2 from the work surface I do have a tendency to wonder - I guess that's inexperience.

 

[a111r]

Too low. 6 LPM gas flow as a minimum. Outside use will need more (unless it's really still weather).
Don't trust the regulator to set it, get a flow gauge (pea shooter) for the shroud. Those small regulators are notoriously rubbish.

Two more tips:
3. Look towards a 10L rent-free cylinder and a 'proper' regulator. Like Hobbyweld 5.
4. Buy Aldi/Lidl £20 angle grinders, so you have them to hand to use (wire cup brush / grinding disc / cutting disc / flap disc) without having to swap them back and forth continually.

 

[eddie49]

Do you find a flap disc cuts down welds faster than a grinding a normal disk?

Use the edge of a thin ( 1/2/3mm ) cutting disk, just hit the top of the weld bead, or the tacks/spot/plug/puddle welds.
Additionally, get a powerfile ( "finger file" ), or try a double-cut tungsten carbide burr in an air or electric die grinder.
Flap disks tend to slide over the beads and thin the surrounding area.
There is a thread about this topic:

Grinding down welds on sheet metal

Hi just wondering what the best practice / best tools would be to take down a weld on automotive sheet metal to get a seemless finish. I have been using a 5 inch angle grinder with a 120g flap disc but I don’t feel 100% consistent and am paranoid about taking it down to far or unevenly. 5 inch...

www.mig-welding.co.uk

 

[Spot the welders dog]

Hi, I have a MIG151en and I am trying to weld 1.0mm mild steel sheet, I am using Argon-CO2 mix gas and 0.6mm wire.

I tried "1 3 MAX" and it worked but the "bacon crackling" sound seems a bit intermittent when doing tack welds. I then tried "A 3 MIN" and the bacon sound didn't change a huge did but the I noticed that my tack welds were concave, almost looking like donuts, and if I held the trigger down a moment more it'd blow through.

Any idea what's causing the concaveness? Is it too much power?

To be honest I find Clarkes "A B C" adjustment settings kind of baffling.

Me too A few years back I was curious enough to poke a MM into my Clarke MIG and came up with some figures.

AFAIK when you choose button '1' and either 'MIN or MAX', button '2&3' become redundant. Switching to button 'A' allows the further choice of either '2 or 3' (min/max).
It looks like you maybe bypassing '2' Min/Max range.
If you have a MM It would be interesting to see what you ranges you discover - esp if there IS any change using button '1' whilst switching between button '2/3'.

 

[Justme]

The manual suggested 2-3litres per minute. I set it to 3 with the trigger pulled. That said I am working outside so that probably isn't helping, I'll up it to more like 4-6.

Another thing I am probably getting wrong is that whilst I am trying to keep the gun about 1/2 from the work surface I do have a tendency to wonder - I guess that's inexperience.

Outside I use 16lpm

 

[dobson156]

Ok I did a little more welding today.

Using a 40grit flap disc was WAY quicker at griding down welds! Haha what are solid Griding discs actually for?!

I ended up having to back the welder right off to the its minimum setting to stop it blowing through the steel on the car.

So either the steel is thinner in this part of the car OR it's a subtly different type of steel which makes it more prone blowing through. When I was welding new metal to new metal it was MUCH more forgiving. I do worry now that I am welding these 2 different steels that the weld might not be penetrating very well into the new metal. Oh well, this isn't a structural part.

 

[dobson156]

AFAIK when you choose button '1' and either 'MIN or MAX', button '2&3' become redundant. Switching to button 'A' allows the further choice of either '2 or 3' (min/max).
It looks like you maybe bypassing '2' Min/Max range.

From the manual. But I doubt those widings are to scale! I don't really fancy going in with a multi meter!

 

[dobson156]

Outside I use 16lpm

When I say outside, I am squeezed into the boot of a car, but the car is outside! My bottles wills last not time at all at 16lpm, but a I guess good welds are more important, I'll try that tomorrow.

 

[Richard Stowe]

Too low. 6 LPM gas flow as a minimum. Outside use will need more (unless it's really still weather).
Don't trust the regulator to set it, get a flow gauge (pea shooter) for the shroud. Those small regulators are notoriously rubbish.

Two more tips:
3. Look towards a 10L rent-free cylinder and a 'proper' regulator. Like Hobbyweld 5.
4. Buy Aldi/Lidl £20 angle grinders, so you have them to hand to use (wire cup brush / grinding disc / cutting disc / flap disc) without having to swap them back and forth continually.

Go for bigger bottles the small disposable's are useless

 

[bricol]

4. Buy Aldi/Lidl £20 angle grinders, so you have them to hand to use (wire cup brush / grinding disc / cutting disc / flap disc) without having to swap them back and forth continually.

I'd be unplugging and plugging in grinders - and then unplugging and plugging in the one I really wanted.

Never really struggled with only owning one at a time - I'm either cutting, or grinding, or flap wheeling or . . . not all of them at the same time

 

[dobson156]

to be fair, I've been thinking about multiple grinders. I really fancy a paddle switch grind for those jobs where it's on and off, on and off. The bosch on I've got is decent but turning it on is a 2 handed operation.

Any advice on butt welding when on of the two materials has a tendency to blow through much faster than the other?

 

[a111r]

You can measure the welding voltage range safely and easily with a DVM, between the torch tip and return lead.

The speed control on those cheap grinders is a novelty to me, as is the owning of multiple tools for an easier life.

Butt welding of different thicknesses and dissimilar on car repairs, that's acquired after some time practising; you have to bias the arc upon the thicker / other material.

 

[Country Joe]

I'd already hit it with a prep disc, but this was to remove the paint not specifically trying to brighten up the metal.

Do you find a flap disc cuts down welds faster than a grinding a normal disk? The welds I did on the car today were pretty ugly and will need a lot of grinding down and it seemed to be taking an age even with a decent Norton grinding disk. I've got some flap discs in a variety of grits, I can try them tomorrow.

Yeah, I don't really ever use grinding discs to take a weld down - I used to use them, but find the flap discs easier.
And yes, it seems quicker for me to use a flap disc.

The manual suggested 2-3litres per minute. I set it to 3 with the trigger pulled. That said I am working outside so that probably isn't helping, I'll up it to more like 4-6.

Another thing I am probably getting wrong is that whilst I am trying to keep the gun about 1/2 from the work surface I do have a tendency to wonder - I guess that's inexperience.

I wouldn't expect 2-3 litres per minute to be enough, even if you were inside.
For a couple of reasons (ok - financial mainly!) I've recently been using co2 as a shielding gas - and it doesn't seem any more spattery than the mix I'd been using.
Having said that, it could be the gap - as I've only used MMA for the last few months.
Quite a big heavy cylinder, but it was only £60, and seems as if it'll outlast me, or until such time as I need a new one, then it'll be another £60 - that's if it hasn't gone up in price during the time it takes me to use it all up.

All the Best,
CJ

 

[Spot the welders dog]

View attachment 283145
From the manual. But I doubt those widings are to scale! I don't really fancy going in with a multi meter!

Never seen that diagram before but it does confirm what I'd thought..
*I only probed the torch/return leads because of a thread some years back asking how 'Clarke' switched power - either 1,2,3MIN - 1,2,3Max or 1min1max,2min,2max etc and was curious.
**As a example; I find '2min' and wire feed around 6.5 works for me to blob together panel work.

 

[Country Joe]

*I only probed the torch/return leads because of a thread some years back asking how 'Clarke' switched power - either 1,2,3MIN - 1,2,3Max or 1min1max,2min,2max etc and was curious.

That's just what I'd (have to) do - but would very likely forget the sequence, and have to do it each time I used it!
I reckon it needs a dial for the slightly older folk amongst us- like me!

In fact, why don't they just do that anyway - surely a potentiometer would be cheaper that a bag of switches - or it it a Clarke USP, type of thing - where it sets them apart from (at least, most of) the rest of the crowd?

All the Best,
CJ

 

[a111r]

It's down to cost, CJ. Not just Clarke, either.
Those three rocker switches are cheap compared to a nice rotary switch with six or seven positions, made up of many components (carrying mains voltage).

 

[Spot the welders dog]

That's just what I'd (have to) do - but would very likely forget the sequence, and have to do it each time I used it!

Tbh Joe, I only done it to find which way round the buttons worked and never thought about it since! 2 Min and fast wire is my happy place