Undoing weld distortion

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Built a wood lathe toolrest from 1 inch diameter steel shaft and 1/4 inch x 2 inch x 16 inch cold rolled steel bar (might be called strap, don't know, but it's those dimensions).  Before welding I sawed off half the diameter for a  1 1/2 inch length, so that the bar would rest on a shoulder to make fitup easier.  After welding a fillet at each side, and the top and bottom, the bar appeared straight, but I did not look carefully.  I wanted more material so I turned up the heat and rewelded each side fillet to deposit more weld material, then noticed that the bar was distorted, each end bent towards the steel shaft.  It appeared that when the fillets cooled, they shrunk and pulled the bar forward on each side.  Each half from the center out are straight, but each 8 inch side has 1/8 inch bend from the center.  The entire tool length is needed for a continuous cut by the chisel, so I need to correct this mistake. I have seen a discussion on weld distortion and how to counteract such but cannot seem to now find that information.   I could perhaps bend back to shape but run the risk of causing a bend in either side, totally messing up any chance of using the rest.  Do I apply heat to the shaft or on the reverse side of the bar to reduce or maybe eliminate the distortion?Hopefully there is a way to undo and thanks for any help.ChrisLast edited by Chris Bar; 02-01-2011 at 05:16 PM.
Reply:Some pics at right angles with the bar close to a straightedge would help, you know.Blackbird
Reply:Chris,I'm not sure as to what you have there. If you have welded 1/4 x 2 mild steel flat bar to a 1 inch solid steel shaft, I would need to know how critical of tolerences you need for the finished product. Too much heat on the shaft could warp the shaft a little. But if you need to correct the flat bar, you could clamp it to a heavier piece of steel like 3/8 or thicker angle iron, etc. Clamp it down tight with two heavy duty clamps, forceing the flat bar straight. Then you could apply heat to the flat bar for a minute or so with a torch, being careful not to heat the bar red hot. Then let the flat bar cool for twenty or so minutes, before removing the clamps. But the question again is how critical is the straightness of the shaft? Too much heat on the bar could transfer to the shaft and cause problems. Or you could just try to cold bent the flat bar. Have I understood your situation?
Reply:The article on weld distortion was apparently not here, and thinking back it probably was in a technical rag.  Anway, the article addressed how to remove distortion without applying mechanical force.No photos here, so think I will just do what is suggested, clamping and applying heat with a torch since there is not much time...I need the tool rest now.   I have made others which turned out fine, but again, I did not add weld material under full heat...a mistake.Thanks for your help.
Reply:Is this the thread you're looking for?http://weldingweb.com/vbb/showthread.php...ght=distortionMiller Challenger 172Miller Thunderbolt AC/DC 225/150Miller Maxstar 150 STLVictor 100CVictor JourneymanOxweld OAHarris O/ASmith O/A little torchNo, that's not my car.
Reply:Thanks, but no.  I realized that is one method to correct the bend, and it is quite close to my situation.  The article I read, well, skimmed very lightly would be more correct, was very technical, and the more I think about it, probably was in a magazine, but I read very, very few magazines now that I am retired.I prefer not to weld on the opposite side of the bar, so will remove part of the fillets, then heat the fillets with the bar clamped in tension to direction desired, so that when cooled, it might stay in that position.  Thanks for your help.
Reply:The Lincoln 'Bible' has a decent discussion of distortion and its prevention or use. Also, remember that steel has a strength of  50, 000 psi or more so those little tack welds have more combined strength that it appears; in other words, you  need to not over-weld and cause excess distortion.
Reply:Which way is the flat bar bent?  Is it bent on the flat side towards the round bar or is it bent along the top edge of your rest?"The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:It is only 1/4 inch thick.  Just bend it.  I would set the bar on two small pieces of wood set on a concrete floor about six inches apart then use a soft face hammer or mallet and strike it at the center where you welded it.   It is better to hit it a dozen times checking after each blow than giving it a supreme wallop and bending it too far.   Next time don't weld so much.  For a tool rest one bead top and bottom would have been enough.
Reply:Well, it's fixed, but not by heating, which did not work, even with removal of significant weld material.  Did see however that the weld was solid, no holes, so my new M211 is doing well.  I weld just for repair and building stuff at home, so anytime I use the MIG, after the first bead, a big grin breaks out....love that machine!  Anyone could weld with that rig.Anyway, since it was bent on the wide side, placed a metal rod under the flat bar and clamped the ends down, which, after the second try, returned the bar to straight.  Not sure why the heating did not solve the problem; assume there was still too much metal that had shrunk and pulled the bar with the weld.Thanks for all the help.  I doubted that bending would do the job...was sure heating would do the trick...learned again.