i weld weld-o-lets of various sizes 1/2 " to 4"to shc.10 pipe 2"-8" to produce fire protection systems.i have trouble with distortion.somtimes the pipe looks like a banana.we use a set of chian clamps which apply pressure opposite your weld but somtimes this doesnt work (ecspecially with smaller diameter pipe).any suggestions to correct this problem would be greatly appreciated.