cutting stainless sheets

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I'm new to this forum, so hello everybody! I've read a lot on it, and it's so great to have all this knowledge in one place.So here is my story:I am making a public sculpture, for outdoors. It's going to be quite large (for me at least) 16' long x 5' depth x 6' high. I've dealt with mild steel before and can manage it somehow. But this time it should be stainless. I am planning to make a frame out of mild steel tubing, but some parts are going to be made out of stainless steel sheet, 304 I think, 12-14 ga. So here is my problem: I just learned that I can't cut it with an OA torch. I've cut some mild steel sheets with a jig saw, but I'm not looking forward to cutting 6' pieces with it. Of course I'll do it if I must. Another way, I think, is to find a source where they'll already precut sheets to my templates, but I think that might be expensive. Plasma cutter...?Does anybody have advice on how to proceed? Any response would be appreciated.Thank you.
Reply:One word - Plasma, my friend!  I use 1/8" tub surround - the white stuff that comes in 4' x 8' sheets at Home Depot or anywhere else for templates.  Use a Sharpie to layout the contour with an appropriate offset to account for the width of the torch tip. Don't like it?  Use thinner to wipe off the line and start again.  Cut it out with a sabre or band saw.  You can easily sand it smooth.  You can go with a small 20amp machine to cut that.  When you are done, sell the machine and you won't lose many $.  Have fun and be sure to post piccys of the finished sculpture...- "If ya can't be handsome, ya may as well be handy!"   HTP Invertig 201Lincoln Power Mig 255CLincoln SP125+Thermal Dynamics Cutmaster 38
Reply:Sounds very good, Garauld. I just checked Hypertherm Powermax 190C Plasma Cutter at WeldersDirect.com for $895.00. It's rated 1/8" mild steel. Do you think it will cut 12GA stainless? Do you think it's a good option?Thanks!P.S. The sculpture has to be finished by the first week of May. I'll post the result's "piccys".
Reply:Gerauld has good points except for the one where he suggests selling the plasma unit after you are done with the sculpture..    This I believe is a bad idea.   Personally I've instituted a poliscy of not selling any of my tools unless I can and am willing to replace it with something better.    So if you buy buy to keep.Now that doesn't mean you have to buy as you can rent.    The problem is once you have had a plasma unit you may not want to go back to the old ways of doing things.Beyond that finding a job shop that has a laser of water jet machine is a real good possibility.   A water jet might be cost effective if the shop is hungery for $$$$.    The problem going this route is that you would almost certianly need a cad file describing the part you need cut out.There are other things to consider also such as how do you expect to weld this up and passivate the SS.   I'd also be concerned about any mild steel in the stucture.   It will require care in assembly to prevent rusting of the stainless steel that comes into contact with the mild. In any event achieving good quality welds on large stainless stuctures is going to be a lot of work.    At work we recently had some welders in doing both conventional steam lines and Stainless Steel process lines.    The guys doing the rather large steam lines went a lot faster than the guys doing the process lines.   Not only where they TIGing those process lines but they where purging the pipe as they went.   Truely beautiful work I might add,    The problem I see for you is this: how will you control the atmosphere where you are welding?ThanksDave
Reply:This is what plasma cutters were made for.  There are other much slower methods, but you'll be glad you spent the money on this project.  Garauld is right about the size machine for that project, but you may want to go a bit bigger with an eye toward future projects...but, that's just a suggestion and not at all necessary for this project.Also, like G. says, take pictures as you go and post.  You could make it like a weekly serial story to keep us updated.There is a big mixed metal (brass, stainless, mild steel...) sculptur across the street from my office (5-points, Atlanta)...it has several stainless sections bolted (NOT WELDED) to mild steel with some sort of sacrificial metal bushings and bolts.  The frame is all mild steel.  It's been there since just before the olympics and there hasn't been any serious rusting problems that I can see.Last edited by smithboy; 04-03-2006 at 02:05 PM.Smithboy...if it ain't broke, you ain't tryin'.
Reply:I certainly like the idea, Wizard, of keeping the cutter towards future projects. That's the thing about outsourcing – you pay once, and the next time start all over. I know some people do it all the time, but I guess I am that kind of person – I like to have my own tools, and do it with my own hands. More control, maybe... As for putting the two metals together, as Smithboy suggested, I planned to bolt stainless sheets to the mild steel frame. I also considered riveting, but it looked like I would have to invest in a heavy-duty riveter. And that would be insane, from the budget point of view, for this project.One thing I forgot to mention: my current garage/shop has a 110V outlet. The new shop is going to be built in a month or so, and the old one has to be demolished - village regulations. So there is no point installing 220 in the old shop, and at the same time I can't wait for the new shop. So where I'm going is: are there plasma cutters (like Hypertherm Powermax 190C Plasma Cutter ) for 110V that can cut 12GA stainless?Thank you guys for your help.P.S. I like the idea of a progress report with pictures. Should I make a separate post, or is here ok?
Reply:Your 4.5 inch grinder will make fast work of stainless sheet.  Mine cuts at about 2 feet per minute through 1/8th inch 316.
Reply:I never thought of using an angle grinder for cutting sheet metal. What disk do you use for that?
Reply:1/16th or 1/8th inch thick discs whatever metal.  Some advertise their use on stainless steel, but they all seem to work just as well on all alloys.  Just be sure to buy a lot, if you're not careful you can burn up a wheel in less than a minute.  It generally get about 4-6 feet of cut out of a disc.
Reply:Thanks, 76GMC1500. I saw some very thin 3/64in. Flexovit Cutoff Wheel on Nothern Tool website. I'll try it.
Reply:I have a friend building a large sculpture with stainless sheet.  As you know, OAC is right out.  He chose not to use plasma because he wanted to preserve the surface finish of the sheet.  WIth plasma, there will be a bit of a HAZ at the edge of the cut.  That can be polished out, but that that would have to be blended with the rest of the surface finish.  Alternatively, you could get some one to water-jet cut it or get a nibbler.-Heath
Reply:I like the 1/16" wheels for cutting.  If you go any thinner, they tend to explode when they bind up.  halbrit mentioned discoloration of the metal when using a plasma torch.  The grinder may also discolor the metal if you try to cut with a lot of pressure on the grinder.  This is just something to consider if surface finish is a major concern.
Reply:It's good to know about discoloration. Thank you, guys for all your advise. In this case, though, I would prefer to expose and even exaggerate some of the artifacts of the craft, if you know what I mean. But again it's good to know the possibilities, and use them in the controlled way. I feel that I ow you a picture of my project, so you will see what I am talking about. It's a model 16”x 3”x 6”, I guess the scale would be 1:12? The title is “Wing”. I'm sorry, folks, I didn't post the pictures sooner. Today I ordered the pipes from Metal Supermarkets for the frame part. When I'm more or less done with the skinny part, I'll make prototypes for the stainless sheet parts using cardboard, so I can see how much I really need.  I hope tomorrow they will deliver my pipes, so I can start. It's hard to work without a helper, but I got a 2-ton engine hoist, I hope it'll do the trick. After all these purchases I'm not sure if I have enough money for a plasma cutter. I found one place in my area, they rent me a PC for around $200 rep week. Will see how it goes. Attached Images
Reply:The sculpture is excellent.-Heath
Reply:I'd get everything lined up so you can make all the cuts in as short a period as possible.  Based on what you say about the scale, you should be able to cut in a day or two if you plan well and get stuff ready before you rent the plasma cutter (get a few extra tips and electrodes if you can).  It's probably not a bad idea to rent...if things go well and you like it, and you see more opportunities to use it, then you can decide exactly what you want kind of machine you want to purchase...with some experience under your belt.Smithboy...if it ain't broke, you ain't tryin'.
Reply:very nice I think that would look great anywhere. should make enough from that one to get a new Plasma cutter when your done.
Reply:Thanks a lot, guys. I certainly hope so. I'll do my best and keep my fingers crossed.As Smithboy advised, I have to plan everything well. The only thing I'm nervous about is the thickness of SS sheets - 12GA. I hope it's not going to be too wobbly. But if I go thicker, then the sheets would be unmanageably heavy for one person. Well, if it turned out to be too thin, then I'll have to reinforce with rods or something like that. It might add to the character. Will see.
Reply:12GA is pretty thick and will turn out fairly expensive.  Since it's a one sided sculpture (I think), you could go with something thinner and add additional support from the back side.-Heath
Reply:You could tack in the supports and then glue the ss to them. That way there would be no weld marks or burnthru on the front side. Just a thought.....
Reply:Looks great. Make sure you post pics of the finished thing in situ.
Reply:I haven't think about gluing as an option. Is it really as strong as welding or bolting, life-wise and strength-wise? I was thinking of bolting or riveting sheets to the frame. I have 3/16” stainless blind rivets with a riveter. I like the look of rivets. I can hammer them to flatten them down a bit. Maybe I got psyched about thicker sheets because I've seen some outdoor sculptures, and almost all of them have about 3/16” sheet steel. Of course they weren't  made in a home garage. But  they do have that absolute solid feel. Are welding marks or burnthrus unavoidable in welding SS sheets?Thanks again for your help!!!P.S. It's a two-sided sculpture.
Reply:An autobody repair man I spoke to said he has seen auto sheet repairs glued in and survive an accident without a hint of failure.  To use it in an auto, you crimp the body with a 3/8 or 1/2 inch flange and glue in the repair patch.  I checked with a local supplier when I wanted to repair my old car.  It was ablut 30 or 40 dollars for 8 ounces of a 2 part batch.  I did my patch the old fashion way.  I don't know how it would work for a panel to support structure, but it should work fine with lap joints between panels.
Reply:That's very interesting, Tech-ad. Thanks for the info. I would like to try it once.
Reply:Hello everybody!As I promised, well... a while ago, but better late than never... I figure. I apologize for such a long delay. And again, thank you all whose advice helped me to complete this project. Here it is - a  sculpture that I finished last spring. It's called Wing. Now it's on display in the Detroit area, at an outdoor sculpture show along Ford Road in Canton, MI. Let's see, where should I start... It all began with a scale model, 16”x6”x3”. Then I had to build the thing full size, which is the same digits, but in feet. The idea was to use a combination of stainless steel and mild steel, and let the mild steel parts happily rust, so there will be a contrast between those materials. It actually happened better than I expected. I was quite pleased with the result. Even after a few months of outdoor conditions the stainless steel parts look as new as they were in my garage, except for some bird droppings here and there.So here we go: some shots of the whole process from start to finish. Attached Images
Reply:some more shots: Attached Imagesyet more: Attached Images
Reply:I estimated the weight of this thing about 1000 lb. So the loading it on the trailer was an issue. Thanks to my buddies (in miserable weather) we successfully loaded it. Of course the truck got broken on the way from Chicago to Detroit. The mechanic said: “I'm not gonna fix your truck until you tell me what's in your trailer!” We told him, it's a part of an alien ship...After all this I learned a few things:Never again should I deal with stainless steel, unless it's a question of life and death. I still have one leftover 3'x8' sheet of 12GA stainless steel. Very heavy.My future sculptures MUST be made in separate modules that I can easily transport and assemble on the spot.Use only stainless steel wire brush on stainless steel. Some spots started rusting, and I had to clean them with a solution. It worked well, but I had to scrub it.What else...