Arc welding 0.8mm sheet steel

Having just read the patent I think I see what the diode does. When the electrode is pulled back by the spring, interrupting the current, the collapsing magnetic field induces a high voltage spike in the solenoid coil, producing a spark from the tip of the electrode down to the workpiece. Kind of like a petrol engine's ignition system, except in this case the buzz box and diode provide the DC power for this Duck Dodgers' Ray Gun gizmo.

Tune in to next weeks' episode - TIG welding with a spark plug!

simondrains said:

Here, George - is this your bit of kit?

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Yes, that's identical - the 'stitch' unit as I think Eastwood describe it. It's the upper of the two photos on their web page, as also sold by Frost and on ebay.co.uk:

I've just remembered where I have seen this gaget before, sold by Rawlplug in the UK so long ago I can't remember when, advertised in the car mags for welding repairs and was claimed to work off a 12 v car battery

Chris.

Here it is, this is the rawlplug version. I haven't actually tried it yet, it was given to me, I wouldn't waste money on it

I tell 'ee what, I bet the electrode quality will make a big difference to the weld. I'd trust an aldi/machine mart special as much with this machine as I would without.

That's it, havn't seen one for so long I didn't think any still existed. But did they work? One way to find out.

Chris.

I'll give it a try when Ive got time, but too busy doing proper welding at the moment.

I had hoped to post the results of a butt metal join using the Kel Arc device before now but I need to work outside and it started raining before I'd got very far yesterday. I'm sorry for the delay. Please do post any results and images from any tests which any of you manage to run with one of these tools, or any other means which you find are successful in joining thin sheet steel (0.7-0.8mm) using a cheap arc welder.

Have you considered spot welding? A couple of turns of heavy copper cable around the welder transformer core should get you enough amps to do spot welding on thin material. On paper very simple - in practice worrying about 1000A. Plenty of videos on YouTube of home-made spot welders (microwave oven transformers seem to be popular for this).

mishka said:

Have you considered spot welding?

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Yes, that's something else I have an interest in! I hope to report results in due course, based on using very cheap components, as you might guess.

With that Kel Arc 'pulse' welding device, I was interested in your take on how it probably works. They say you can shut off the pulsing and just use the diode if you want. I haven't tried that yet. But I wasn't aware that diodes acted to reduce current, like they say or imply. Any thoughts?

GeorgeB said:

With that Kel Arc 'pulse' welding device, I was interested in your take on how it probably works. They say you can shut off the pulsing and just use the diode if you want. I haven't tried that yet. But I wasn't aware that diodes acted to reduce current, like they say or imply. Any thoughts?

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If you're feeding it from an AC source then the diode will only conduct during the positive (or negative, depending on which way round the diode is connected) half of the AC cycle. In effect the effective current ('effective' in a heating sense ... mumble RMS mumble) is halved.

That's starting to make sense to me now (though the ray gun seemed another good explanation).

So the diode halves the current by getting rid of half the electricity. And to stop the arc going out the vibrating brings the rod closer to the work to maintain the arc than pulls it away to give a better length for actual welding. Added to that a coil discharging a little bit every now and again to maintain the arc? Is all this going on at 50Hz then or is it cleverer still?

I would have said 50Hz as that's the mains frequency (unless your stateside then its 60Hz)

I'm pleased to report that the Kel Arc welder seems to do what it says on the tin in that it makes it quite easy to work on thin steel sheet (0.7-0.8mm) without blowing holes. They say in the instructions that you need to practice and I clearly do need a lot more practice, even in basic arc techniques on thicker metal, let alone with the Kel Arc.

I cut a small piece of steel sheet (about 3" long) in two with a hack saw. The gap was therefore the width of the blade. After 2 or 3 runs with the Kel Arc, the metal was joined and the most important thing for me is that I blew only one hole at the end. That's the least of my worries. I'd increaed the amps from about 45 to 80 in an attempt to get better penentration and it still didn't blow holes. The avoidance of nearly all holes is a major breakthrough for me, without any copper backing. Here is the test piece:



I then decided to turn the arc welder's current back to the minimum (45 amps) and try 'capping' the weld with a 6013 rod, on it's own, without the Kel Arc. The underlying weld must have helped me avoid blow holes then, as well. I am sure a competent arc welder could have laid a perfectly neat bead at that point. The messy appearance is a reflection of my lack of much basic skill:



The avoidance of holes is the good news but the rear of the panel shows grossly insufficient penetration. Again, it's the least of my worries. I can figure out how much to increase power, to get the penetration, in due course:



The reverse side splatter is from earlier experiments.
You can see from the straight line that there is only one hole, at the end.
I didn't bother tacking the join in advance. The three spots (pentrated joints) seen on the reverse are from the Kel Arc.

Well well!

George - interesting start. Next time you do it, i'd suggest tacking, as that will help stop the prep gap from closing up, so improving penetration. (as you will have noticed, there is no gap at all anymore)

simondrains said:

Well well!

George - interesting start. Next time you do it, i'd suggest tacking, as that will help stop the prep gap from closing up, so improving penetration. (as you will have noticed, there is no gap at all anymore)

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Simon - many thanks for pointing out why the gap had closed. I noticed and wondered how/why. I was going to buy or make some 'Intergrips' like Frost sell but was keen to try out the Kel-Arc again a.s.a.p. I can't understand why penetration was better on plain sheet rather than joining a gap.

I'm pleased to have made a move forward in dealing with thin sheet on an arc welder. Once I've cracked the fundmentals like no holes and penetration, I'll try and move towards improving the appearance and uniformity of the weld.

mishka said:

Have you considered spot welding? A couple of turns of heavy copper cable around the welder transformer core should get you enough amps to do spot welding on thin material. On paper very simple - in practice worrying about 1000A. Plenty of videos on YouTube of home-made spot welders (microwave oven transformers seem to be popular for this).

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Mishka - as a direct result of your post, thank you, it reminded me to get on with my idea of trying to build my own spot welder. Many accounts on the Internet are for welding battery termimals but my sole focus is car body panels. The other suggestion of using a joggler fits in well. I'd like to compare 'proper' spot welds from my DIY device (if it works) with 'spot' arc tacks as I mentioned before, all on 0.7-0.8mm steel sheet. If this goes much further, I'll open a new thread under 'projects'. Four turns of thick copper wire produced 2.4v which might be about right given that the Clarke spot welders say they work on about the same voltage. Yes, there should be at least 1000A available. Scary!

The Clarke devices quote 3000A plus and times from 0.1 secs to over 1 second. If it's a function of time and current that means I might need 0.3 secs as the minimum. I hope to be able to hold some sort of 'switch' closed by hand for anything from 0.3 secs, rather than need complex timing devices before the device is even proven. For all I know it may immediately blow a 13 amp fuse, or even my 30A cooker socket.

If you decide to buy one of those contraptions, don't forget to pick up a set off ear defenders! I had one of those, very weird noisy thing to operate.

metaljoiner said:

If you decide to buy one of those contraptions, don't forget to pick up a set off ear defenders! I had one of those, very weird noisy thing to operate.

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Do you mean a Clarke-type spot welder? I didn't expect any noise so thanks for the warning. Is that from the shot of current or the mechanical clamping action, or what?

probably from the energy from the spark its self