I want to weld the face of a 1/4" mild steel plate (6" x 6") to the end of a mild steel tube (3" x 3" x 1/4" x 48"). This is for the gantry on a metal CNC mill I am building. My question is how do you weld the two pieces using MIG and have them at exactly (or as close as possible) to 90 degrees or at right angles? The flat plate will be bolted to the floor or a frame so that the tube will stand upright vertically.
There is or course the welding magnets, but I would rather clamp the two pieces together using C-clamps so that any warpage from the weld can be compensated for until I get all welds done. Is there a trick to using the magnets?
The method I have primarily used is to use a piece of angles where I clamp one side of the angle to the tube and the other to the plate and since the angle is at perfect right angles, the plate and tube should also be at right angles after the weld. However, I have found that if the plate is not exactly flat then you will not get the perfect right angle. Maybe i can use thicker plates to get the flatness I need.
Any suggestions of recommendations is welcomed. I want to do this stuff right the first time to save time and money.