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**mael** · (This post was last modified: 04-28-2012 10:43 PM by mael.)

I'd like some advice on how to set up a plasma torch.

I have tried to learn how to make one, but I'm not satisfied I've got all the info I need.

Is it an arc which is between the workpiece and a tungsten rod, and the tungsten rod is kept cool enough so it doesn't melt by a stream of high pressure air?

To make one, would I basically have (say) a 35V DC supply forming an arc at several tens of amps which is started by a small HV sparker, and the air will be directed so as to both keep the tip of the tungsten rod cool, and concentrate the arc in a narrow circle?

I saw homemade plasma cutters with large resistors, and this is the part I can't understand ... why the need for a huge resistor?

Am I looking at converting a small benchtop stick welder by running a high pressure line to the outside of a tugsten rod - with an old stove sparker to start the arc?

How to use ... (My guess) ... start the sparker to start the main arc, and increase the length of arc to stop it.

Compressed air must be flowing momentarily before the arc occurs so that the electrode isn't melted. (What pressure air in kgs/cm)?

What am I missing - I've got all the parts I need - I think. Though I'm confused about the resistor, and the other thing is whether I have to get a special head, or if I can adapt some pipe and use some sturdy tungsten rods which were used beore as the starting electrodes in an oil furnace.

Please help to me to learn all I need to know to get going. I'm trying to find an easier way to cut steel than using the trusty old (very noisy) angle grinder.

**LoP Guest** lop guest User ID: 49382 04-29-2012 01:19 AM

making a plasma cutter yourself sounds dangerous make sure its safe

**silversides**

Wear welders goggles. Look at what you need to do then close your eyes as you weld.

**Luvapottamus**

Simple & powerful plasma cutter that you can build at home for under $300! It cuts up to 1/2 inch steel. This is what I made to cut sheets of 316 stainless for building hho cells. It makes cutting stainless like cutting butter. I found that 4x8 foot sheets of 316 cost only $150 so I needed a way to slice them up.
Please be aware that there is an error in the schematic at the end which will keep it from working correctly. This video was made in a hurry. I will post some move videos with all the correct info if anyone cares.

Engineers told me it was to hard to do and it would take them a year to design a plasma cutter. However, if plasma cutting was invented by accident during world war two then I knew I could do it on purpose. A home made torch head is super cheap, however I choose a replacement torch head because they have better air nozzle control and make a smoother cut; $125 of the price was spent on the "replacement" torch head.

I have sold plans in the past, but really this is just to good of a tool to not let everyone know how to build one. So this is my gift to the DIY community..

Please note that in this schematic the inductor and water resistor needs swaping, otherwise it will not work!. The resistor can not be in the torch wire it must be in the work clamp wire.

http://www.youtube.com/watch?v=6W3tLDBdPQQ

Here's his Youtube page, maybe you can ask him questions?

http://www.youtube.com/user/cheaphardwarez

**mael**

Thank you very much. I understand more now.

I'm using my biggest BR on my welder now, so I might have to rummage around in my box :) to find something else. Actually I might try putting a few BRs in parallel.

I'm on 100V here in Japan. So I take it I just rectify the wall current? For some reason I thought I'd be using somewhere less than 50V - I see there is a danger involved! Well I'm no stranger to electricity, it's just that I've never built a plasma torch before.

I take it I'm pretty free as far as the specs are concerned, and overbuilding it is preferable to having weak parts start smoking. OK!

The resistor. 12 Ohms? Is that for 100V? What sort of wattage does the poor resistor need to tolerate? As it is 100V, what resistor (if any) is required?

12 Ohms at big amps is going to mean a pretty large amount of heat generated - hence I see the need for it with 220V At 100V it's still going to be over a kW, isn't it!

I know I'm asking for free, but I have to say the schematic isn't the best I've ever seen. I wanted some details on how to fabricate the head.

What I'm planniing to do is to get one working, and once I get it going I'll either make it better or buy one. I just want to get in the door now, so to speak.

When I first started thinking about what a plasma cutter entailed I had visions of powering up my 8kV transformer - and I thought that can't be right. I was imagining what kind of gloves I'd need to stop 8,000V arcing through onto my hand. (ha ha).

I'm pleased it's just rectified mains, and I'm glad we've only got 100V here.

In a way, this is a stick welder with compressed air blowing the arc away from the rod, isn't it?

I need to cut some curves and holes, and you know what that's like with an angle grinder - not impossible, but a real PITA.

If you can fill me in on the extra questions I have here, then that'd be great.

**mael**

I think I understand the resistor now. If I don't have something then I'm just going to trip the breaker every 5 seconds.

I've got several heating elements that are variously between 5 & 20 Ohms - That's a relief.