DOM tube warping issue

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Hey guys great site you have here. Im looking for some help with some tig welding i am doing. I am tig welding a piece of 1.25"od dom to a 3" x .25wall honed dom tube and the welding is causing the internal threads on the inside of the 3" DOM to warp. So installing the aluminum end cap isn't very fun. As you can see in the pic below i milled a flat on the tube so it would make it easier mating the two tubes together, but i think im going to eliminate the flat giving the main tube more beef. Also, i was thinking of making a dummy steel end cab which will screw into the end of the tube with another dummy tube to slide over the OD of the 3" DOM while im welding and leave them in until the weld cools. think this will help the warping issue guys? if not what else can i do? thanks for the help. thanks kyle
Reply:If you re-size your images( before uploading) to 800 wide x 600 high pixels--that allows the full image to be displayed, plus preventing your text from being chopped off.Welding on the side of honed tubing will create distortion.Can be lessened by using doubler plates, intermediate connection fittings--but not really eliminated.Threading anything inside, then welding is asking for lockup of the threaded part.You may need to consider post weld machining and threading.Blackbird
Reply:sorry didn't see that prob from the pic. below is the original post i hadHey guys great site you have here. Im looking for some help with some tig welding i am doing. I am tig welding a piece of 1.25"od dom to a 3" x .25wall honed dom tube and the welding is causing the internal threads on the inside of the 3" DOM to warp. So installing the aluminum end cap isn't very fun. As you can see in the pic below i milled a flat on the tube so it would make it easier mating the two tubes together, but i think im going to eliminate the flat giving the main tube more beef. Also, i was thinking of making a dummy steel end cab which will screw into the end of the tube with another dummy tube to slide over the OD of the 3" DOM while im welding and leave them in until the weld cools. think this will help the warping issue guys? if not what else can i do? thanks for the help. thanks kyle
Reply:blackrock1-what is the function of this part?2-Are my responses to your questions in post 2--unsatisfactory, earning me the grade of 'F'?Blackbird
Reply:Looks like a hydraulic cylinder to me.  Why did you block out the piston in the pic?  Coping in the smaller tube is a better plan than milling a flat on the big one.  It will still distort though.  I agree with Dave that threading in a part prior to welding is asking for a locked up part.  I've tried it before and will not be doing it again.  I don't care how many people say it will work.My name's not Jim....
Reply:Looks like a fancy high dollar off road bypass shock.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Originally Posted by DualieLooks like a fancy high dollar off road bypass shock.
Reply:I don't think this one will be fixed. The threads and o-ring fit will be too out of round for a proper fit.If it an be bored oversize, you will need an oversized gland.
Reply:Originally Posted by RojodiabloYes, but it sounds like an expensive off road pile of scrap metal to practice on.......Blackrock, the best bet for welding a shock body is to get an internal sleeve so you do not warp the tube. We have used them, made and threaded to fit so the threads are kept round, and the tube kept round. The sleeve acts as a heat sink, and it helps to keep more even heat for less distortion.I'd just finish welding that one, and then take it to a machine shop to fix the flaws you have built into it. I am sorry, but there is no other easy answer.
Reply:have you guys ever heard of "Heat Fence" or "Rapid Cool"? can someone school me on this stuff and would it help my problem thanks kyle
Reply:It looks as though he is buying some parts then modifying them (welding) so i would venture to say that the threads are already cut in the piece,  He is gonna have to figure a way to protect the threads during the welding process I think.  From what I understand your gonna have to do like mentioned and make a piec that will thread into the shock while your welding it to help protect the threads.  As for material, Im not certain and im sure some of these guys can be more help there.  if this is a sealing point for the shock internals I wish you the best of luck keeping the threads true enough to seal after welding.Hypertherm PM 1000 on a CNC TableMiller Maxtron 450 - S52A series feederHobart Handler Lincoln 155 (my sons he's 11)looking to sell or Trade a RFC-23A foot pedalCustom diesel parts fabricator
Reply:depending on what the parent material is cooling it to quickly as im sure you know will cause it to be brittle.  I doubt your offroad application is going to be cohesive with that.  Alluminum would be my first guess for a controlled heat sink.  if that tubing is chromoly your pretty much screwed as the cooling on it needs to be VERY slow anyway.Hypertherm PM 1000 on a CNC TableMiller Maxtron 450 - S52A series feederHobart Handler Lincoln 155 (my sons he's 11)looking to sell or Trade a RFC-23A foot pedalCustom diesel parts fabricator