I bought a Plasma cutter last year and wrote a feature about it for "Brit Chopper" magazine. Whilst this is a UK based tale, it should apply everywhere, and I hope it will help. To be quite honest, this is the best thing I've bought in years. This is a direct copy of the feature, click the pictures to enlarge.
PLASMA CUTTER
You’ll see elsewhere that my latest project is a car, and a hell of a lot of sheet metal work is involved, so I decided the best tool for the job would be a plasma cutter, as I’d owned one years ago. How do I explain how a plasma cutter works easily, when I’m not actually sure myself? I always thought they were a pretty recent invention, but they were developed during World War 2 to speed up the cutting process. In layman’s terms they use an electrical circuit to excite the atoms in compressed air, turning it into a superheated gas, “plasma” which is directed through a small nozzle. The plasma is negatively charged, and a positive lead from the machine is connected to the item to be cut. Once a supply of compressed air is added, it’s ready to go. The plasma stream will cut through virtually any metal with virtually zero distortion, and on sheet metal, will cut so fast it has to be seen to be believed. It literally blows the metal away and is a super-clean process leaving very little slag. Depending on the model you have, it will happily cut from wafer-thin to 1” plus, and the output power is adjustable. The plasma stream is actually visible as it exits the nozzle.
So…..it’s definitely what I needed, and I borrowed one off Mexican John. Now, my old one was big, but this one was huge, but I was grateful of the loan, as they’re expensive bits of kit, but the only problem was that it had been in storage for years and wouldn’t let me play, and anyway, I’m not happy borrowing other people’s gear, so I decided to hit eBay and try and buy a used one. That really opened my eyes, because the price had come down so much over the years and stuff that would have cost £2000 ten years ago was now £200…..brand new, so I started browsing after getting a few pointers from the lads on our forum. The choice was vast, and looking at the adverts, one thing became blatantly obvious, these were all the same(ish) units with different cases or stickers on them, and I was 99% sure they all originated in China, which didn’t particularly worry me. I had worked out what I wanted mine to do, and that was to cut from 20 gauge to 8mm thick steel without approaching the machine’s maximum power, and last for the duration of the car build. I settled for a “CUT 40” optimistically rated at a 10-12mm cut by the suppliers. There were also CUT30’s CUT50’s etc, the numbers indicating the power, and mine had to run on single phase.
eBay’s great, but I try not to buy tools etc. second-hand, I always wonder why they’re selling them, if they work well, keep them I say, so I decided to go for a new one. After checking out loads of prices, they seemed to come out at between £160-£200 plus carriage. I’m also not a fan of haggling, being outbid or, in the excitement of the auction, paying more than I meant to, so a quick look at all the suppliers was in order. I decided on a firm called “Cobel Engineering” mainly because they were the closest (incase it furked up on me) and rang them, asking to speak to the gaffer. They usually auction all their stuff, but I said “Let’s cut to the quick, what’s your best deal”? He started at £265 and we settled at £210 plus £25 next day delivery, and I was happy with that as it had a 12 month guarantee and I knew where they were. Right….product test.
The carrier dropped it off and my first thought was “Fucking hell, it doesn’t weigh much, I reckon I’ve bought a load of crap”. It was also a lot smaller than I expected, not much bigger than a large battery charger! As usual, it was a self-assembly job, but nothing a 6 year old couldn’t do having read the translated instructions. However, its manual did explain its small dimensions and both baffle me and make me laugh at the same time, like this bit…
”This cutting machine is manufacture with advanced inverter technology. With high-quality component MOSFET and PMW technology, the invertor converts DC voltage, which is rectified from input AC voltage, to high 100KHz frequency AC voltage; as a consequence, the voltage is transformed and rectified. Therefore, it results the much more small sized of the main transformer and lighter in weight of the inverter welder, which rates the performance of welding by 30%” and also “Connect the copper screw on the cutting torch to the output terminal of the one-knob of the front panel and fasten it towards clockwise direction to avoid gas leaking”.
Phew, lost me there mate, but anyway, I managed to hook it up, and somewhat sceptically switched it on, expecting a puff and a bang. Bloody hell, was I surprised, I tried it on some 18 gauge and it sliced through it like a hot knife through butter, and then I tried it on some 6mm plate and it did the same, but a little slower, and for the last few months it’s worked faultlessly and done everything I’ve asked of it (and more). It came with two spare tips and I’m still on the first one, having cut up all the 4” x 2” box section for my chassis with it as well as loads of heavy duty brackets. I was expecting it to gobble up air, but it uses hardly any, and I’m only running it at 80psi. It still cuts nicely at 40psi so I reckon you could happily run it off a small hobby compressor. Once the pressure gets too low, it will cut out. I’ve hooked it into the 30 amp supply, and the only problem I’ve ever had is the odd blown 13 amp fuse in the cutter plug after a real long heavy cut.
It took a day or so to get used to it, and one tip I can give you is to route both the airline and torch leads away from where you’re cutting (after I burned a hole in the airline). I tried wearing a welding mask, but couldn’t get on with it, a pair of dark shades or welding goggles are fine, but personally I don’t use either. With sheet metal it will cut as fast as I can pull the torch along, and I use a piece of 2” x 2” angle iron as a guide on straight cuts. Freehand took a bit of getting used to as my hands tremble slightly (hic) and on thick stuff it will bevel, but once you’ve got it sussed it’ll cut through at 90 degrees by angling the torch. Different steel thicknesses require different “pull” speeds. It will leave a bit of slag on the reverse side, but it’s easily chipped off, with all that’s needed to give it a perfect finish being a light sand with an angle grinder. I’ve used it on 6mm aluminium and it’s amazing. One advantage of its light weight is that it’s easily moveable about the workshop, but as it has a 3M torch lead, I don’t have to move it very often.
So….to sum it up? Brilliant, excellent value for money, I don’t know how I’d have managed without it, and it’s probably reduced the time spent cutting and grinding by 75%. It’s amazing how the size of electronics has been reduced over the years, whilst at the same time, efficiency has increased tenfold. I took the cover off so I could show you what’s inside, expecting to not see a lot, possibly a transformer at most, but it’s completely crammed with electronics. Take a look at the picture of my CUT40 sat on top of Mexican John’s old machine. You’d expect his to be ten times the power of my puny looking bit of kit, and here’s the amazing thing…..John’s is only a CUT30! Don’t be afraid of foreign imports, some of it’s bloody good.
