Thread: Spot welding - ideas for a custom electrode setup

I've boxed myself into a corner somewhat and could do with some ideas to get me out.

Have a cheapie spotwelder which works great for 1.2mm panel steel (when you put it on the 2.0mm setting).
Been doing some rust/fatigue repair work on the rear door of my daughter's Landrover, and it involves bent top hat sections with a flat piece spot welded on the bottom to support the open side.

Here's the welder:





Here's where I've got to with the door:





You can see where I've made some of the spot welds, and have marked with a texta where the next ones would go.

I did think about spot welding the flats on the bottom of the hat sections before assembling and welding the pieces in place - but decided not to for various reasons. Because the spot welds are all close to the edge of the flange, I thought I'd be able to just poke the welder in and weld it.
Unfortunately, the length and height of the welder and the short distance to the next member means the electrodes are on about 45deg angle to the surfaces and won't weld. The arms are too short to come in from the outer edge of the door - so that's not an option either.
Worst case is I'll drill some ~5mm holes in one of the pieces and just do a mini plug weld with the mig. I'd prefer to spot weld them if possible though.

I'm thinking of making up some sort of a remote connected electrode arrangement connected by short heavy cable back to the welder
Imagine a small G-clamp with one electrode isolated from the clamp body...Clamp it onto the work, then trigger the timer on the welder.
Clamp doesn't need to have a deep throat as all the welds are close to the flange edge.

Any comments or alternative suggestions.

Steve

Not actually a suggestion, but thought I'd mention my experience.

I’ve never been impressed by spot welds. Car manufacturers do them all the time. They seem to work for them. Robots. The engineers have plenty of practice to ensure it happens correctly. I suppose. One would hope they test their products and manufacturing processes from time to time.

I used to work for Simpsons & Pope. A holiday job while I was a student. One of the jobs I was given was to spot-weld brackets to small hood-like things. I think the item was something to do with a cover for an air vent. Not a crucial component.

I was given some instructions. I asked how they knew the weld took. Oh, yeah, he said. Every now and again drop one of them on the floor. If they stay in one piece they’re good. If they come apart adjust the time or current a bit. Yes, quite a few fell apart when they hit the floor.

Have you tested your welds yet? Try using a hammer and belting the hell out of them.

Yes, definitely tested the welds as soon as I took it out of the box.
With 2 bits of the 1.2mm and set to the 1.2mm setting - the welds would come apart with little effort when pulled apart.
On the 2mm setting you can see the metal go a nice red color very briefly when doing the weld, and significant force is needed to pull the 2 bits apart. Usually ends up with one piece pulling a lump out of the other one.

Steve

Hi Steve, would you be able to get some brass/copper bar and make longer arms for it?
I'd give you mine but it's going to Stawell Monday or Tuesday.
By the way, what brand is your spot welder?
Kryn

I worked in a automotive parts factory for a while and one of my jobs was sorting out the quality of the spot welding. For such a simple looking process, it can be full of traps for the unwary.

For a start, tip size is critical. The idea is that you need to get to a level of Amps per mm2 to get a decent weld. People not familiar with the process crank the amps up if the weld is poor (as Errol's supervisor suggested he do), but if the tips have started to mushroom, all you are doing is supplying more heat to make the softening of the tips happen faster. I used to be able to look at a spot weld and tell whether it was good or not. Haven't done it for years so probably out of touch, but the welds in your photos look a bit marginal. (The tell is the amount of heat discolouration around the spot - it should be pretty tight = high heat; small area) For a small tong welder like that (I have a tong welder too, but quite a bit older), probably the biggest tip size is something like 2mm in diameter, maybe up to 2.5mm.

The plan you have posted may not work all that well. The other part of spot welding is pressure; the material being welded must be constrained so that the weld is under pressure. If you see sparks shooting out when someone is spot welding, that usually is molten metal escaping from the weld and likely shows that the weld will not have 100% strength. I made some extension arms for my welder some time back to weld the bottom seams of a box. I'll head out to the shed later and get a photo or two.

In the meantime, in this video https://www.youtube.com/watch?v=TqcJFPvAxNQ I do a bit with spot welding. From memory, the first part is about spot welding and the second about cross wire welding.

Michael

Thanks Michael.
I knew about the electrode diameter but hadn't thought too much about how they would soften and enlarge. I'll definitely check them.

Understand about the pressure aspect, which is why I was thinking that the G-clamp arrangement might be an option.
My logic was that it would be easy to apply initial pressure, and hopefully enough flex in a lighter clamp that the pressure wouldn't be lost as soon as the metal started to soften. Do you think I'm missing something?

I do have some brass round bar here that I could make longer arms out of, but I was concerned about potential resistance from using brass instead of copper, and the longer arms maybe not providing enough pressure.

Kryn - the welder is an AlphaTools brand one from eBay.

Steve

This is my spot welder with the extension jaws I made for it. They clamp either side of an electrode and then another electrode is clamped in the tip
IMG_0981.JPG IMG_0980.JPG IMG_0979.JPG
Rather than make any extensions out of brass, I would suggest Al, as it has way better conductivity. I see your welder has screw on tips, but you could probably make a similar extension to cope with that.

At the risk of encouraging you to follow my (bad) habits, can I suggest that you think about how to adopt your welder to take a through electrode like I have here (although this is stock for this welder). The reason being is that if I have to dress my electrodes, I can just slide them up a bit. Yours look like a tip that maybe can be dressed a couple of times but then has to be chucked away because it is too short.

Michael

Thanks Michael.
Those extensions look great - I'll look into making something similar.
To be honest I hadn't paid much attention to the electrodes, and didn't even pick up they were a screw in type! I'll deal with that in due course too.

Steve

Had a visit from a friend today and I was showing him what I was doing with the door repairs and the spot welding.
I explained the issue with not being able to get the spot welder electrodes in without them being on an almost 45deg angle - therefore it wasn't going to work.

His response was "can you just grind a 45deg angle on the electrodes so they sit flat?"

....... So damn obvious but it never occurred to me!!

After he left I did exactly that. Took a bit of faffing to get a round face on a conical electrode and have the 2 opposing faces match up nicely - but I got there in the end.
Worked perfectly, and I got the remainder of the spot welds done easily.

For those wondering about the strength of the welds, after shaping the electrodes I did a test on a couple of small bits of the 1.2mm panel steel.
Welded them and then tried pulling them apart, and even driving a cold chisel down beside the spotweld.
I reckon its more than strong enough for what I need





Steve

Originally Posted by ErrolFlynn

Not actually a suggestion, but thought I'd mention my experience.

I’ve never been impressed by spot welds. Car manufacturers do them all the time. They seem to work for them. Robots. The engineers have plenty of practice to ensure it happens correctly. I suppose. One would hope they test their products and manufacturing processes from time to time.

I used to work for Simpsons & Pope. A holiday job while I was a student. One of the jobs I was given was to spot-weld brackets to small hood-like things. I think the item was something to do with a cover for an air vent. Not a crucial component.

I was given some instructions. I asked how they knew the weld took. Oh, yeah, he said. Every now and again drop one of them on the floor. If they stay in one piece they’re good. If they come apart adjust the time or current a bit. Yes, quite a few fell apart when they hit the floor.

Have you tested your welds yet? Try using a hammer and belting the hell out of them.

23 year's ago i had to pull a damaged front left and rear quater panel's from a Ford Festiva i can assure u those spot welds are so strong it took me day's to peel the rear left quarter shell off the car those spot weld's were so strong if i drilled just off center it gave me grief just trying to rip the rest of the tack off, they blunt drill bits like crazy too

Originally Posted by gazza2009au

23 year's ago i had to pull a damaged front left and rear quater panel's from a Ford Festiva i can assure u those spot welds are so strong it took me day's to peel the rear left quarter shell off the car those spot weld's were so strong if i drilled just off center it gave me grief just trying to rip the rest of the tack off, they blunt drill bits like crazy too

It's the easiest welding method, too.

I have a welder missing an electrode.
To make a replacement, is there any advantage to use copper instead of bronze?

Originally Posted by nadroj

I have a welder missing an electrode.
To make a replacement, is there any advantage to use copper instead of bronze?

Use copper if possible. Spot welders work on resistance, so the lower the resistance in the electrode/ machine interface, the better off you will be

Michael

Originally Posted by gazza2009au

23 year's ago i had to pull a damaged front left and rear quater panel's from a Ford Festiva i can assure u those spot welds are so strong it took me day's to peel the rear left quarter shell off the car those spot weld's were so strong if i drilled just off center it gave me grief just trying to rip the rest of the tack off, they blunt drill bits like crazy too

hey i know this is about a year late- but, you can take a concrete drill, the - type not the + type, and you can sharpen the tungsten carbide tip using angle grinder
and with a bit of frustration it can actually get sharp enough to cut- and boom now you have tungsten carbide drill, which can drill hardened metal- and silly spotwelded stuff.. how many holes in just mild steel can one of those things take would also be interesting to answer.

Hi Guys,

I've reground masonry drills many times in order to use them on hard materials, its not difficult. I also have a set of carbide tipped drills that are intended for drilling hard stuff like the chilled skin on cast iron.

Its also how I drilled 4 mm holes in hacksaw blades !

Years ago, I visited a chap who made reproduction body tubs for early Land Rovers, Series 1 80" models from 1948 to 1953. He showed me the spot welding process he used for the Aluminium panels, the original tubs were a alloy called Birmabright i think.

This guy used a normal medium sized industrial spot welder, it was a back yard workshop set-up in a suburban house block. He showed me how he uses a thin stainless steel ( may have been plain steel ) sandwich between the welder tips and the 1.2mm Aluminium sheet . He made long extension arms for the floor section, it has top-hat shaped pieces underneath. I have pics of all this setup somewhere, I must find them.

This might help for general small spot welding tips ( tips as in help ! )

https://www.autospeed.com/cms/a_113277/article

https://www.autospeed.com/cms/a_113279/article

https://www.autospeed.com/cms/a_113278/article

The chap who made the early Land rover tubs is also a Range Rover /enthusiast collector https://www.landrovermonthly.co.uk/a...ion-australia/