O/A 1/8" pipe to 1/2" plate

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I am using an OA rig and would like to weld 1/8" wall round pipe to a 1/2" sheet steel so that the pipe works as legs on a table.  I have a few questions:1. The victor tabel recommends a #4 tip for 1/4" - what size tip do I need?  I am thinking that this will melt the pipe too fast.  Do I really want full penetration into the 1/2" sheet or do I just want penetration equal to the thickness of the pipe wall?2. I am having trouble seeing the inner cone of the flame, it just looks like one really bright cone once I add O - is it safe to look at the OA flame without the #5 shield?3. Is the diameter of the filler important or can I use 1/8" for just about any thickness and just vary the speed at which I add filler?4. It seems as though the soap stone lines are hard to see when cutting - is there a better more visible way to mark surfaces for cutting?5. I assume that fitting the pipe to make a "T" joint means I need to cut the end of one piece (the leg of the T) to match the edge of the top of the "T" - seems as though the cutting torch is the best way to do this.  Am I being too careful about a snug fit before welding, should I just cut the pipe with the grinder and fill in the space with filler?thanks in advance.Glen
Reply:You will have to bring the half inch plate to temperature or you will just blow holes in your pipe. I wish I knew what size tip you need. I have never tried half inch plate with oxy acetylene. I use a giant tip to weld sheet metal. But I move very quickly. Usually when you are short of heat, you tend to use a smaller filler wire. When I have plenty of heat, I only use a 1/16' wire.        Sincerely,             William McCormick
Reply:Not saying it cant be done, but I doubt you will be able to weld to 1/2" PLATE (1/2" thickness is not sheet) with an O/A torch.  Even if you can make it stick, forget about getting any kind of penetration on the plate.  If this is going to be for a table, its very likely that the top will break off after some use or sideloading and crush your legs or the legs of those around you.  Just dont do it, get a buddy to arc weld it for you.Have we all gone mad?
Reply:Originally Posted by sn0border88If this is going to be for a table, its very likely that the top will break off after some use or sideloading and crush your legs or the legs of those around you.  Just dont do it, get a buddy to arc weld it for you.
Reply:Gwiley,I just completed a similar project, so maybe I can help.  I used 5/32" wall tubing and 1/2" plate that I'm using for a railing.  I'll put some comments/answers below your questions. Please note that I'm not a professional weldor.   Originally Posted by gwileyI am using an OA rig and would like to weld 1/8" wall round pipe to a 1/2" sheet steel so that the pipe works as legs on a table.  I have a few questions:1. The victor tabel recommends a #4 tip for 1/4" - what size tip do I need?  I am thinking that this will melt the pipe too fast.  Do I really want full penetration into the 1/2" sheet or do I just want penetration equal to the thickness of the pipe wall?I don't exactly recall, but I believe I used a #4 tip.  A good point from William is to preheat the plate.  I heated mine until it was orange, and used a 3/32" rod.  I used a center punch to mark the plate with a series of dimples, and then I flame cut holes in the plates.  I then inserted the tube into the plate, and welded around the top of the tube, and then around the bottom.  The challenge of course is to not destroy the tube.  If you preheat the plate and point the flame at the plate, there will be enough radiant heat to melt the rod and the tube.   2. I am having trouble seeing the inner cone of the flame, it just looks like one really bright cone once I add O - is it safe to look at the OA flame without the #5 shield?3. Is the diameter of the filler important or can I use 1/8" for just about any thickness and just vary the speed at which I add filler?4. It seems as though the soap stone lines are hard to see when cutting - is there a better more visible way to mark surfaces for cutting?5. I assume that fitting the pipe to make a "T" joint means I need to cut the end of one piece (the leg of the T) to match the edge of the top of the "T" - seems as though the cutting torch is the best way to do this.  Am I being too careful about a snug fit before welding, should I just cut the pipe with the grinder and fill in the space with filler?thanks in advance.Glen
Reply:Originally Posted by sn0border88Not saying it cant be done, but I doubt you will be able to weld to 1/2" PLATE (1/2" thickness is not sheet) with an O/A torch.  Even if you can make it stick, forget about getting any kind of penetration on the plate.  If this is going to be for a table, its very likely that the top will break off after some use or sideloading and crush your legs or the legs of those around you.  Just dont do it, get a buddy to arc weld it for you.
Reply:Are some people intentionally blind?  Read what I said again.  I dont think HE can do it.  Someone with more experience with an OA torch I know it can be done.  A novice user will get absolute minimal penetration on the 1/2"plate in a fillet weld setup at BEST.  I would expect to be able to break the leg off with a few good sledgehammer swings after its done being "welded"Hey, when it breaks off ill bet you'll be glad you didnt waste your time and money just getting it welded.Last edited by sn0border88; 06-03-2010 at 12:13 AM.Have we all gone mad?
Reply:Sounds as though I am biting off more than I can chew.  I'll see if I can get some help from a friend with an electric setup to hook the legs up.Would it be crazy to fab up the legs and bracing around them then take the whole piece to someone to attach it to the plate or is it better to weld the legs to the plate THEN add bracing etc.?