What does a plasma cut look like?

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I had to get some 3mm plate cut this week to make something. Six pieces to make a box - the reservoir of my much thought about and talked about water feature.I could have cut it up myself with my 9 inch angle grinder, but it would have been fiddly and I'm having a lazy week.The steel supplier charged me $44 for guillotining (minimum half hour charge) and because two of the pieces were odd shaped, he said they'd have to use the plasma cutter - another $44.In hindsight, I'm having a very lazy week.So I went to pick up the pieces and one of the straight cut bits was out by 10mm. I suggested it might be an idea in future to 'measure twice and cut once'. He gave me a look that communicated well the fact that he wanted to hit me but wouldn't because I owed him money.The odd shaped pieces cut by the plasma cutter weren't terribly straight and didn't match - they were supposed to be mirror image. They also looked like they had been done by an angle grinder.So what does a plasma cut look like? Are they hard to drive i.e. are they like a knife or like a torch?I told him that given he was charging me $44 for 'plasma cutting' I hoped they had actually cranked up the machine.He gave me that look again.Scott
Reply:Results vary, a lot depends on the machine and operator.  I've see cuts that looked like they were done by a sheer, and others that resembled a bad cutting torch.  Sounds like you got the later of the twoLincoln 255 w/Prince Xl Spool GunLincoln Precision Tig 185Thermal Dynamics Cutmaster 35 (too small)
Reply:its more like a torch.  You can make em look real good...or real bad.  Its in operator, tip quality which is resultant on operator, machine adequacy which should be assesed by operator, and in general clean up will make a differnce, which is made by operator.  Therefore you should have hit him IF it Catches...Let it Burn
Reply:Okay. I reckon they probably used the plasma cutter, but used it poorly.I was too outnumbered to hit anyone. I haven't hit anyone since high school, anyway. Even then I only did it once and came off second best. I'm a quick learner. I can generally throw a comment at someone that will make them feel like they've been hit even if it takes them a minute or two to work it out. I just make sure I'm out of reach by then.Scott
Reply:lol  Nah Scott, takes a real man to hold back and not act like a donkeys rear.  However, I will say that in my opinion youve learned a valuable lesson here.  Never put tight tolerances on these guys...they will let you down every timeIts the same thing here tooThese arent the craftsman you find posting on this forum.  They are gernally general labor who are told to make cuts and such.  Often they arent skiilled or give a hoot about what their doing.  Its sad, but the realityIF it Catches...Let it Burn
Reply:I'll agree with all of the above in that the results vary.   I just got a Mitech Cut40 Plasma Cutter ($474.00 on Ebay) and am yet to make a decent looking cut.   Steel cuts better than aluminum.   In fact the cuts I made on 1/8" aluminum look like I did them with a chainsaw.    It seems like if I turn the heat and air up near all the way, I will leave a better cut edge.    I watched the techs at my plant whip through some 1/2" steel plate with a plasma cutter and leave an edge that looked like it was cut with a bandsaw blade, so I know good results are possible.One thing I have learned, if I want dimensional accuracy on odd shaped cuts, I have to make a plywood template for the nozzle to ride against.There are no small projects
Reply:Originally Posted by imagineerOne thing I have learned, if I want dimensional accuracy on odd shaped cuts, I have to make a plywood template for the nozzle to ride against.
Reply:Did they cut these by hand with a plasma cutter, or did they use an automated plasma cutter?By hand, its dependant on how many beers you had last night, or how much coffee this morning.How straight you hold the torch, how consistent you can be about standoff distance, whether or not you clamp on a guide, like a piece of angle, to run the torch against.I used to cut 3/4" plywood templates, and run the edge of the torch against them, to get multiple parts, and with practice, you can get pretty good at it.But most big steel processors use cnc plasma machines- much more accurate, good clean edges, with maybe a slight bevel in thicker material.
Reply:Originally Posted by RiesDid they cut these by hand with a plasma cutter, or did they use an automated plasma cutter?By hand, its dependant on how many beers you had last night, or how much coffee this morning.How straight you hold the torch, how consistent you can be about standoff distance, whether or not you clamp on a guide, like a piece of angle, to run the torch against.I used to cut 3/4" plywood templates, and run the edge of the torch against them, to get multiple parts, and with practice, you can get pretty good at it.But most big steel processors use cnc plasma machines- much more accurate, good clean edges, with maybe a slight bevel in thicker material.
Reply:I bought a piece of 1/4" plate cut-to-size two weeks ago.  They cut it with a handheld plasma cutter with a straight edge guide.  Looks just like a shear.  I made a comment to the guy about how nice it looked, he held it up and you could see very small consistent imperfections.  He said that was his heartbeat moving his hand.  Just a quick pass with a file and it was flawless.Gonna have to get me one of them!
Reply:Here are a couple of pictures of hand plasma cuts using a straight edge on about 3/16ths.  This is right after the cut, so nothing else was done here.  The thing to notice is that the cuts are pretty clean as compared with a oxy/ace cut.  Not that some folks can't do wonders with a regular torch, but a plasma cutter is easier to make clean cuts with. Attached ImagesSmithboy...if it ain't broke, you ain't tryin'.
Reply:i can do that with a torch on 1/4" and thicker....thinner is tough.........need guideIF it Catches...Let it Burn
Reply:Isn't that a great line:'That was my heartbeat moving my hand.' Can't wait to use that one day.
Reply:I would like to remind you guys : only take with a grain of sand , what salesmen & manufacturers say about cutting capacity their Plasmas will cut. What ever they say it'll cut, just believe it'll cut  HALF  that thickness . My bosses at Mare Island told me that , & so did my friend when he owned welding store .
Reply:Well, okay.  I don't know about half.My Miller Spectrum 375 was rated for 3/8", quality cut at 1/2" and a sever of 5/8".I routinely made high-quality steel cuts in 1/2" and severed 3/4" with it on several occasions.Now, in aluminum, it maxed out at 1/4"
Reply:These arent the craftsman you find posting on this forum.  They are gernally general labor who are told to make cuts and such.  Often they arent skiilled or give a hoot about what their doing.  Its sad, but the reality[/QUOTE]I find this statement to be highly insulting.Last edited by spuddown; 05-01-2006 at 02:16 AM.
Reply:I am sorry you find it insulting, yet it is true.  Are you implying you are the target of this statement?  You will notice I did not state everyone in these positions is as above stated.  Therefore if you are in this type of occupation and are insulted by this statement you should reconsider your own self.   If you are not, then this does not apply.  However, it is exactly as stated.  While there are possibly some decent hands in these jobs, by and large, the majority of folks arent craftsman who care a lick about what there doing.  They are there for a pay check.   If you find it insulting maybe you should consider these individuals have a choice to continue doing what they are, or they can learn to do better.  Welding is a skill, it takes practice and preserverance to obtain the necessary ability to do the job right.  Noone is born with the gift to weld or fabricate.  This comes from experience and hard work.  If an individual doesnt care about what he is doing he will never try to make himself better.  He will not care about the workmanship he is making, like in the case of Scott's piece of stock that was improperly cut.  IF you think this is an insulting statement I made, consider how insulted Scott was when he found the piece he is paying good money for and to have cut was cut like a bear, or in Scott's world a salt water croc, just chewed into.  If the shoe fits....wear itIF it Catches...Let it Burn
Reply:Yep Spuddown, Tx was generalising. I routinely pick up timber that has not been cut correctly by the 'guys out back'. I thought for some reason that the 'guys out back' in a steel supplier would have paid a bit more attention to what they were doing. Pretty illogical.There would be some guys in that position who do indeed take care with what they do, and if you happen to know of any in Sydney, Australia, please let me know.
Reply:Were talking about two different things here. The fact that someone in a fab shop in Australia made a bad cut hasn't got anything to do with the people that post on this forum. Your statement has to do with people that post on this forum, I'm new to this forum but have been reading it for a year or more. I think there are a lot of craftsman that post here, also I think alot of them care about the quality of whatever they are making, whether it be a hobby or not. The fact that their asking questions here makes me believe this. Thats like me telling scott that anyone in the states that work in fab shops aren't craftman because the real craftsman are in construction or the shipyards. Oh by the way, don't you work in a fab shop?  Now I don't think everyone that works in a fab shops not  craftsman, also constuction has a bunch of losers working there too, but you can't paint everyone that posts on these forums with the same brush. If the shoe fits wear it? Your a funny guy!
Reply:Originally Posted by spuddownWere talking about two different things here. The fact that someone in a fab shop in Australia made a bad cut hasn't got anything to do with the people that post on this forum. Your statement has to do with people that post on this forum, I'm new to this forum but have been reading it for a year or more. I think there are a lot of craftsman that post here, also I think alot of them care about the quality of whatever they are making, whether it be a hobby or not. The fact that their asking questions here makes me believe this. Thats like me telling scott that anyone in the states that work in fab shops aren't craftman because the real craftsman are in construction or the shipyards. Oh by the way, don't you work in a fab shop?  Now I don't think everyone that works in a fab shops not  craftsman, also constuction has a bunch of losers working there too, but you can't paint everyone that posts on these forums with the same brush. If the shoe fits wear it? Your a funny guy!
Reply:After rereading my entire post I may understand what confused you.    Its the same thing here tooThese arent the craftsman you find posting on this forum. They are gernally general labor who are told to make cuts and such. Often they arent skiilled or give a hoot about what their doing. Its sad, but the reality
Reply:Originally Posted by scott brunsdonYep Spuddown, Tx was generalising. I routinely pick up timber that has not been cut correctly by the 'guys out back'. I thought for some reason that the 'guys out back' in a steel supplier would have paid a bit more attention to what they were doing. Pretty illogical.There would be some guys in that position who do indeed take care with what they do, and if you happen to know of any in Sydney, Australia, please let me know.
Reply:Originally Posted by TxRedneckSpud,Obviously youve misquoted me.Now we got that resolved lets have a
Reply:Most steel yards I've done business with aren't in the business of makeing precision cuts. If they told you they will then they definetly should but most of the time I buy steel the shops around here will cut it off an inch long or so and let you make the finish cut. I've also had them bend sheet metal in there break that was wrong and left it on their shop floor. If its not what you order don't be a nice guy, make them redo it. If a guy is wasteing alot of steel and he's one of the guys that your talking about, he should and needs to be weeded out. The price of steel these days it should be done right.
Reply:A properly done plasma cut and an OFW cut are going to look similar.  The difference you will notice if you look very closely is that the plasma cut will produces less slag, there will be less discoloration around the metal due to the lower heat input, but the most important difference is that an OFW cut cannot produce a perfectly square edge.  About midway through the thickness of the metal being cut, the gasses will exand a little bit and remove a bit more metal.  The difference is small, but can be a problem if very, very tight fit-up is required.Boys, Boys, Boys, Let's All Take A Step Back. I'm A Newby To This Site My Self. The One Impression I Get Is That All Of You Are Trying To Do Some Fab Jobs Accurately, Easier, And With A Great Deal Of Pride. One Of You Was Disappointed With The Quality Of Work You've Come To Expect Of Youself. This Happens All Over, From A Good Cut In Steel To One Rotton Egg In A Dozen. S@$t Happens. Myself, I'd Find A Store Where I'm Comfortable The Eggs Will Be Fresh, Every Time. [bad Analogy?] I Did See Some Good Input. For Instance, E-bay. Look For The Quality Name, Ie; Miller,thermal-dynamic, Lincoln, Esab,hyper-therm. I Sell Plasma Equipment, And I've Seen The Quality Of Many Brands. The Preceding Brands Were Head And Shoulders The Best Out There. Now, Can We All Just Get Along..... Good Fabbing To All!!!