How to weld sq tube together and keep it square

by tim
(nh)

I am trying to weld two pieces of 2 inch sq tube 1/8 thick, at a 90 % angle. I square them tack them and then weld. When I finish they are out of line. Is it the heat that throws them out? Please help...


--------------------------------------------------

remember that the metal shrinks when it solidifies and cools. the joint will always try to draw inward. so either tack it with that in mind or weld in a direction that prevents drawing inward.