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Old 10-16-2007, 06:46 AM
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plasma cutter

I may be S***in in the wind here but it looks like they would make an adapter of some kind that could convert a AC/DC reversible current Arc welder into a plasma cutter.

IIRC a plasma cutter simply starts an arc, melts the metal and compressed air blows it away.

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Old 10-16-2007, 07:59 AM
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conversion

They do it's called a air arc & it sucks
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Old 10-16-2007, 08:52 AM
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Quote:
Originally Posted by John Belt
They do it's called a air arc & it sucks

And that is with a capital "S"!

While an Air Arc is a different piece of equipment meant for a different job (mostly weld removal and beveling out cracks for welding prep) some of the smaller Plasma cutters are nothing more than glorified Air Arcs. A true Plasma cutter is far more than just an arc melting the metal and then using air to "blow away" the molten metal and in fact uses a separate gas mixture to form the plasma. These true Plasma cutters are a lot better than the small ones and will cut much thicker material. As far as the Air Arc except for something like maybe stainless weld removal I have little use for the darn things and they have been the cause of literally millions of weld failures. They will bevel out a crack or remove a weld easily and fast but they also leave the area HEAVILY contaminated with excess carbon, a LOT of excess carbon and not just lying on the surface. If anyone here is using Carbon Arc equipment for ANY welding prep on their car frame or on anything else BE SURE and grind every trace of the carbon from the surface and slightly beneath the surface, the big problem comes with areas that are hard or impractical to grind. I would much rather use a torch with a grooving tip for weld removal or to prep a crack for welding but unfortunately this is rapidly becoming a lost art even though it is many times better than that danged arc gouge.
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Old 10-16-2007, 09:28 AM
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Has anyone used the Hobart Plasma Cutter

http://store.cyberweld.com/hoplcuai25.html.

It looks like a nice little unit and is priced respectably. I was thinking of making it my next big purchase. Any thoughts out there?
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Old 10-21-2007, 08:19 AM
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Plasma Cutter

About a year ago, I bought my first plasma cutter. Did a lot of reading and bought a Chinese one by a company called Riland. To this day, I have used the HECK out of it. It's a 40a unit. Runs on 220v, uses compressed air for the Plasma, and it's also a TIG welder! I bought it off of EBay and till this day, I never regret the purchase (even though the same unit now is going for only 400 and was 600 or 800 when I bought it). The company that makes it is Chingzen (sp?) And they make several other name brands, mostly they all look the same and work the same. Consumables are cheap. All there is for the consumables is a copper electrode, ceramic swirl cup, copper tip, and the ceramic shield. The plasma cutter is the little box below the Clarke.

Here is a section of Peterbuilt truck frame that I cut up and welded together to make a welding/plasma table.
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Old 10-21-2007, 09:08 PM
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Air arc

Quote:
Originally Posted by oldred
And that is with a capital "S"!

While an Air Arc is a different piece of equipment meant for a different job (mostly weld removal and beveling out cracks for welding prep) some of the smaller Plasma cutters are nothing more than glorified Air Arcs. A true Plasma cutter is far more than just an arc melting the metal and then using air to "blow away" the molten metal and in fact uses a separate gas mixture to form the plasma. These true Plasma cutters are a lot better than the small ones and will cut much thicker material. As far as the Air Arc except for something like maybe stainless weld removal I have little use for the darn things and they have been the cause of literally millions of weld failures. They will bevel out a crack or remove a weld easily and fast but they also leave the area HEAVILY contaminated with excess carbon, a LOT of excess carbon and not just lying on the surface. If anyone here is using Carbon Arc equipment for ANY welding prep on their car frame or on anything else BE SURE and grind every trace of the carbon from the surface and slightly beneath the surface, the big problem comes with areas that are hard or impractical to grind. I would much rather use a torch with a grooving tip for weld removal or to prep a crack for welding but unfortunately this is rapidly becoming a lost art even though it is many times better than that danged arc gouge.
I have to totally disagree with you about the use of the "air arc" or as I know it the carbon arc torch, or gouger. I have used a carbon arc torch on a daily basis over the years for "back gouging" welds in ASME code vessels and never had a problem with it affecting the quality of the weld. Most of these welds were X-rayed when complete and were of the highest quality.
In the hands of an inexperienced operator it could leave some traces of carbon, but it would most likely be due to running too low of an amperage setting which would not clean the weld properly in the first place. It takes a welding machine with the capability of around 300 amps or more to make the torch perform properly.
I never found much use for them in automotive applications, but if done right, you could remove a weld and have much less grinding to do than with a scarfing tip.
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Old 10-21-2007, 09:57 PM
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41 we will most definitely disagree on this one and I too have been using the darn things when necessary since 1968 and for welds requiring certification also. I did not say I did not know how to use them and I have used up to 5/8" jointed rods at nearly 1400 AMPs and I am ALL TOO WELL familiar with the dang things and the procedure. I have done this little test MANY times (even won a few bet$ ) to convince people who think a carbon arc torch does not damage the metal. Scarf a piece of scrap metal as clean as you can with that thing then test the surface with a hardness tester, you will be in for a shock at how hard the surface is and how deep it goes! You don't even have to use a hardness tester, just hit a spot on the metal that has not been scarfed with the pointed end of a chipping hammer then hit a spot in the scarfed area and look at the damage to the hardened point on that hammer, that scarfed surface will even chip the edge of a chisel! This has NOTHING to do with skill it is just the nature of the beast and if you are welding over a scarfed surface no matter how clean it looks without grinding it first your welds will suffer for it- guaranteed, not necessarily fail but they will not be all they could be unless the surface is ground clean first. I much prefer to use a torch with a gouging tip because it will leave a much cleaner surface that needs only brushing and it is a heck of a lot faster, I would put my torch up against a carbon arc torch any day for cleanliness. I regularly used my torch (a Victor 1600) with a #12 grooving tip to gouge out cracks as much as 14" deep and several feet long in some cases (Dragline bucket lips). Try telling Caterpillar Tractor, Marion Power shovel or EASCO that a carbon arc torch is ok to use without grinding!

Last edited by oldred; 10-22-2007 at 07:12 AM.
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Old 10-22-2007, 05:39 PM
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plasma cutter

OLD RED, I have read many of your posts since I have been a member on this site and I don't doubt your skill or experience. I have also been a welder since the 60's, and anyone that has been doing it that long has to have learned quiet a bit along the way even if they are just sitting in an office and giving orders.
I joined this site to learn as much as I can about everything automotive related. I feel I can always learn something and will never know it all. I have worked in plant maintenance, been a machinist, a small engine mechanic, a welder many times, and also worked in a sheet metal shop. Not counting all the misc jobs I had as a kid. I have also been a supervisor in a few of these places and much prefer working with my hands. I guess what I'm trying to say is that I'm not a rocket scientist, but I have been around a little.
When you start talking about metal hardening from a carbon torch being used you might want to take a tour around a good side fabrication plant. Gougers have been used for many years on all kinds of structures and if they caused those kind of problems then they would not be allowed in any ASME code shop.
If you think that using a scarfing tip to cut or grove out a seam or to remove a weld doesn't cause the metal to harden, then you need to get out your books and start studying again. They create a lot of heat and are much slower than a gouger. If we were a little closer I would love to be able to prove my point, but I'm pretty easy to get along with and don't want to continue this discussion as an argument.
From most of your posts that I've read you seem to be determined to be right regardless, and if that makes you happy then so be it. But I know what I'm talking about and that is the end of my opinion on the subject.
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Old 10-22-2007, 08:41 PM
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41 What do you think happens to all that carbon and graphite in that rod? The air blows it into the molten puddle and nowhere near all the molten metal is removed, a good deal of it solidifies with that heavy carbon contamination and that is what causes the hardened surface. If you weld on this surface that carbon winds up in the weld and the base metal and this is what causes the problem. I did not discover this myself and it is not just something I assumed, it is a known problem and I learned it years ago while attending welding seminars sponsored by welding and equipment manufacturers, I did not just make it up. As long as you have been doing this I am surprised that you are not aware of it. Some manufacturers, such as Caterpillar tractor and ESCO, are quite clear about the use of these things and welding over that surface is simply not allowed for the very reason I mentioned. A torch gouging tip hardens metal? Try that little test I mentioned on metal that has been scarfed both ways, just try it! Apparently you have never used a torch with a large gouging tip and anyone who is proficient with one can tell you that it will do a much cleaner and faster job than a carbon arc torch. Honestly have you ever tried to gouge really heavy stock with a #10 or #12 tip? Have you ever seen anyone use one that really knows how to do it? If so I honestly don't see how you could say a carbon arc torch is cleaner or faster. I have used, as did most everyone else on those jobs, both extensively and I would ten to one rather use the torch for both speed and quality of the cut. What was preferred did not matter much anyway since on most critical welds carbon arc was not allowed, it was Oxy/Acethylene or a Plasma gouge when the Plasma was practical.

Last edited by oldred; 10-23-2007 at 12:55 PM.
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Old 10-22-2007, 08:43 PM
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Ut oh, it's another "I've been a welder for XX years" battle. Just sit back and soak it all in boys. You know where this is going when they start stating AMPS and quoting ASME standards.

Sorry, I could't resist. I have the utmost respect for guys that have been doing this all thier lives and it's discussions like this us amatures learn good information.

Ding Ding Round three!
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Old 10-22-2007, 09:44 PM
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Those Clarkes are good lil welders ain't they I have one just like it .
I myself like the plasma cutters better than the air arcs....much much quieter ...Those doggone air arcs are loud.Of course a torch is Virtually silent
Shane
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Old 10-23-2007, 08:05 AM
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The point about the air arc is that if anyone does use one on something like a frame, and it would be quite handy for removal of riveted brackets and welded parts for example, just be sure and grind off any area it is used on. These things are easy to use and only require a welder and compressor but cost a couple of hundred bucks so unless you will need it for something else or can barrow one then they may not be a good idea. The big advantage to them is the fact they will cut stainless, etc but if used for plate they will leave a very ragged edge. Sorry for going out in left field (again ) but I honestly felt like it would be a serious mistake for someone to make a weld on a critical frame part after using one of these things and not properly preparing the surface first. They are very common and as I said could be very handy for a variety of things related to car frames and probably are used quite often but if so it needs to be done right. Arrow you are certainly right and I apologize but I honestly feel that using one of these things and not following up with proper prep could lead to serious problems on something as critical as a frame and I tried to pass on the info I have and give the reasons I have for doing so.

In my first reply here about this subject I said that a smaller Plasma cutter was "nothing more than a glorified Air Arc" but that is not entirely true and could lead to a misunderstanding. The Plasma cutter does indeed leave a very clean surface and when used properly this surface can be welded without further prep, that is one of the big selling points of a Plasma gouge vs an Air Arc. The basic operating principle of a small Plasma machine is about the same as an Air Arc but it has a tungsten tip instead of that Carbon/Graphite rod that burns away quickly leading to the contamination of the base metal. There are a lot of those little plasma cutters out there, and most do a really good job, but I am certain there are a heck of a lot more Carbon arc torches in use and since they were mentioned I thought this info might be relevant.


Decided to do a search on this subject, was not at all hard to find info. Check out the Cleaning, edge preparation and fit up section on this welding tech site.

http://www.haynesintl.com/Fabric/FBw...paration%20and


About halfway down the page here explains it pretty well.

http://www.thefabricator.com/Cutting...le.cfm?ID=1346

Last edited by oldred; 10-23-2007 at 12:54 PM.
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Old 10-25-2007, 09:12 PM
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Speede
One thing I noticed about the Hobart, before I bought my Miller, was that the air compressor is built into the unit. Eveyone I talked to said that one of the most important things about your air source is that its clean, and free of moisture. I have 3 seperate filter/traps on my air line.
I dont know how you would clean up the air on the Hobart. Moist air in, mist air out.
Not that I'm dogging their welders though which I feel are top notch!

-Art
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Old 10-30-2007, 09:07 AM
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Quote:
Originally Posted by Art Deco
Speede
One thing I noticed about the Hobart, before I bought my Miller, was that the air compressor is built into the unit. Eveyone I talked to said that one of the most important things about your air source is that its clean, and free of moisture. I have 3 seperate filter/traps on my air line.
I dont know how you would clean up the air on the Hobart. Moist air in, mist air out.
Not that I'm dogging their welders though which I feel are top notch!

-Art

Thanks for pointing that out, I thought they were all run off external air. i just want a nice cheap little portable unit for around the shop. Cutting up cars, nothing major.

Sorry to the others if it looks like I tried to hijack your thread!
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