Welding Tips and Tricks

I'm welding 1.25", 14ga square steel tubing. 2 8" pieces cut at 45 degree to make a corner. What's best practice in terms of welding sequence to avoid the dreaded shrinkage that will leave me with an 85 degree corner when I'm done? Fillet first? Tack all 4 corners and then weld the sides? Start with the outside seam and work in? Thanks in advance for any tips on this.

Clamp the dog piss out of it using squares.

I prefer to tack midway on the outside for all 4 corners. Then I tack the inside corners, middle of the tubing. Take your time. One outside seam fully welded. Opposite outside, fully welded. Then I move to inside of the two unwelded seams. Do the opposite inside. Let it cool down while clamped.

Once cool, unclamp and check for square and flat BEFORE you welded all 4 corners inside and out. Adjust as needed (welding inside if the angles are >90, weld the outsides if at or less than 90.)

Once it’s cooled, weld the flat faces paying attention to warpage. Go slowly, keep it fully clamped while welding and while cooling. You’ll still probably have to tweak it flat as you go (nature of welding metals).

Good. Going over to do it right now. I'll let you know how it goes. But certainly no problem clamping the DP out of it! ;)