Oil-cooled welders

Hi folks,
I'm pondering the question of whether I need a bigger welder. I currently have a Cytringan "Bantam" 180 A oil-cooled machine. It's
almost identical to the more common Pickhill and Oxford "Bantam" sets. Perhaps users of these British oil-cooled machines could give me their thoughts here?
I have build a lot of stuff using 3 mm thick mild steel. My current welder copes with this comfortably. A while ago I switched to using 6011 electrodes instead of 6013 because I wasn't happy with the strength of the welds I was getting and was also having some problems with slag inclusions in awkward welds. 6011 electrodes are giving me much stronger welds, but need a higher open circuit voltage to strike an arc. So now I am using the 80 V terminal on my welder instead of the 50 V terminal.
This is still fine for welding 3 mm and 4 mm steel with 3.25 mm electrodes as it gives an output up to 120 A. But I have bigger projects in mind. I want to make a chassis for my phase convertor and a frame for a hydraulic press. These will require at least 6 mm steel. I want the welds to have a similar strength and stiffness to the parent metal. In other words I don't want to be using thicker steel for little gain. So I want to keep using the 6011 electrodes which I've been very pleased with. But I'm not sure that I'm going to get adequate penetration in a single pass using 3.25 mm electrodes on my current machine. I'm not sure if I should move up to 4.0 mm or 4.7 mm electrodes. And I don't want to be struggling with a task of which my welder is barely capable.
So does anyone have strong feelings about whether or not my welder is up to the job? If I was to get another machine I would almost certainly go for another Oxford-style oil-cooled machine. Probably a 300 A @ 50 V / 200 A @ 80 V machine. A fine current adjustment would be nice too. I believe there's a machine in the Oxford range which roughly meets this specification. I also like the really old cube-shaped English Electric machines, but I'm not sure that they have an 80 V output. Anyone in the Midlands got an idle machine they want to sell?
Best wishes,
Chris
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Christopher Tidy wrote:

Would you not do multiple passes on 6mm? With properly vee'd plates this would surely be the way to ensure proper penertation and sound weldment. Im not qualified, though I have taken a welding course at the local college, and there we were taught to use multiple runs on 6mm plates. In that case wouldnt the smaller electrodes do fine, even if it takes slightly longer to make the completed weld.
Dave
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On 27 Sep 2006 00:14:39 -0700, " snipped-for-privacy@bem.fki-et.com"

A 180A set is going to struggle with some varieties of 4mm rod, others it will be fine. Try a different variety of 6013, Murex Zodian Universal are good and easy to use, though I prefer Vodex (harder to use) for verticals. Both are pricier than some, but the cheaper rods often have more flux which is more likely to give you trouble with inclusions. As for welding 6mm plate, I would use 3.25 for most welds anyway, with multiple passes where needed. I'm not a qualified welder, but have done many hours of welding 6mm plate, & used nothing more than a 180A Oxford for about 20 years. BTW I've got a 250A Oxford set looking for a new home. It's old & scruffy, it has dual voltage and fine control, it works fine but there seems to be a *very* slight oil leak from the tank since I put fresh oil in it 6 months ago. I presume that if you're thinking of a 300A set you have a 3-phase supply to run it?
Tim
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Tim Leech wrote:
<snip>

I was hoping to avoid multiple passes if possible. I find that single passes are neater and less trouble, especially on short welds like the ones I'm planning. Maybe that means I need more practice at welding, I don't know.

I was really looking for something trouble free, but I'll bear it in mind. Whereabouts are you? Dutton is somewhere near Warrington, isn't it? Any idea of a price you're looking for?

No, but I'm under the impression that the RT300 is the biggest Oxford that can be configured for single phase. I might not use it at 300 A right now, but I was thinking that if I'm going to have two Oxfords, I might as well buy some extra capacity now, rather than regret not having it later!
Thanks for the advice.
Best wishes,
Chris
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On Wed, 27 Sep 2006 09:36:10 +0000, Christopher Tidy

75 quid? There must be a few quids' worth of copper in it, at current prices <G> The oil leak is *very* slight, I've washed it off a couple of times to try to find the source but no luck. The level doensn't go down noticeably, but there's a 'damp' patch on the floor after a few weeks.
BTW it's too heavy for a normal car boot.
Tim Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
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Tim Leech wrote:

Sorry I've taken a while to reply. I've been away. 75 sounds like a fair price. As I said, I was really looking for something completely trouble free - I already spend lots of time fixing machines <G> - but I'll bear it in mind.
I bought some 4 mm electrodes today to try out on my 180 A machine. Some 6011 and some 6012, both "Weldrite" brand. I asked about Murex Zodian and Vodex, but the local welding shop isn't a Murex distibutor, so they didn't have them. Hopefully these rods will give me a better idea of whether or not I need a bigger welder.
I'll let you know how they work out.
Best wishes,
Chris
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