How to shape stainless so it fits?

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I am taking 2 tubes of stainless and trying to weld a flange onto it.Almost like a collector. The stainless is pretty thick. How do I get the shape of the 2 tubes coming together to be round like the flange?Is there a way to get the metal more malleable so I can try and shape it?
Reply:Not quite sure I am envisioning what you want but I'll try. I'm thinking of making it a 3 tube joint with the 3rd tube being very short to weld the flange on. The other way I see it is like a y with the 2nd coming into the 1st on an angle if this makes sense.You would cope or notch the pipes to achieve this if thats really your question. I'll try and see if I can find a pict to post.
Reply:Maybe I'm describing it right.I have 2 pipes that are welded together. When you look at it head on, it makes a shape like an 8 except with no wall in the middle.I need to connected to a circular flange like an O.So somehow I need to expand the 8 to an O shape so I can connect it.
Reply:It may be easiest to cut the pieces to fit in the 8 shape, but form them with a hammer and anvil to an O shape before welding them together.
Reply:Originally Posted by EngloidIt may be easiest to cut the pieces to fit in the 8 shape, but form them with a hammer and anvil to an O shape before welding them together.
Reply:Here are some pics of the thing
Reply:Should be easy enough to hammer into shape, but the question is..."Is the circumference of the '8' the same as the circumference of the 'O' that I'm looking for."...what I mean is that you can knock that into a perfect circle and it may not be the diameter that you need. I'm not faliliar with the adaptor your welding on to it, but I assume that you want it smooth on the inside.I'd say a piece of 1-1/2 square stock or similar would work good. Weld it to the top of the bench with about 5 inches overhanging the top...slip your collector over it and with a dead blow hammer(unless you want to make a real mess), or something with a soft face massage it over the flat top of the square stock. You want to work on the top and bottom of the '8' where the radius is too tight. As you start to open that up, it will take shape.
Reply:I do want as close to the same circumference. I think it'll be close. I have no way of making them exact. I'll just have to do the best I can.One of the issues I have is that I'm not sure I can "smack" the metal into shape. It's maybe 1/8" thick, maybe 3/16ths. I'm not sure. It's 321 stainless. It just seems very very stiff. Much more than the plain steel I've worked with before. Any way to soften it? Or should I just really give it hell. it will take quite a bit.  Originally Posted by TinbasherShould be easy enough to hammer into shape, but the question is..."Is the circumference of the '8' the same as the circumference of the 'O' that I'm looking for."...what I mean is that you can knock that into a perfect circle and it may not be the diameter that you need. I'm not faliliar with the adaptor your welding on to it, but I assume that you want it smooth on the inside.I'd say a piece of 1-1/2 square stock or similar would work good. Weld it to the top of the bench with about 5 inches overhanging the top...slip your collector over it and with a dead blow hammer(unless you want to make a real mess), or something with a soft face massage it over the flat top of the square stock. You want to work on the top and bottom of the '8' where the radius is too tight. As you start to open that up, it will take shape.
Reply:Perhaps a short tapered mandrel to widen the narrow part and pull in the sides. I would start with something as close to the desired dia as possible. and then go to progressively bigger sizes. Drive it in to expand the opening to round. Be sure to lube it so it wont stick. Heat would certainly help but I don't know if thats the way to go in your application.
Reply:You could try an exhaust tubing expander (the type you use a wrench to expand),  you might have to have more than one size as im not sure how much they will expand.  If you dont want to buy one take it to any exhaust shop and they will have a hydraulic mandrel type expander on thier bender and it probably wont cost more than a few bucks to have it done. Matt
Reply:All good ideas. Thank you guys. I will try one of these.