I've built three work tables using 2" square steel tubing, 1/16 wall thickness. All have had tops with mitered 45s at the corners and one or more center cross pieces. The tables range from 2'x2' to 2.5'x6'.
My issue is the warping or flatness of the table top after welding. I weld these clamped on a flat welding table. One had about 1/8inch deviation from flat and the worst was about 1/4inch deviation. The 1/4inch case I straightened using a bottle jack, which worked well.
Two questions -
1) Is there a welding sequence that will minimized warping. I watched Jody's video on welding a mitered corner and distortion from 90degrees, but this is different.
2) What warpage is reasonable. My perfectionist expect the finished top to be flat, but this may be unreasonable.
Any chance on getting a video addressing this. Thank you in advance,
So there is a couple things that play into ever changing variables...
The thickness of material used (1/16" wall) can greatly effect the warpage. The weld itself is smaller than your pinky finger and think about pushing the material on a table.... you can push thinner material way more than thicker material and so does the weld when your fabricating. The thicker and heavier material used helps fight warp cause it's more difficult for the weld to move it around. ( I understand that this might not be able to change just saying it's a variable to consider)
Another thing is the weld after welding... say your table is a rectangle frame with 4 legs and some plate on top... the welds on the rectangle after you weld can "pull" the base metal a bit and I found that grinding all the welds flat can help to relax the frame. (Got to bevel the base metal before welding to be able to grind flush)
Another (I think the biggest) thing is no matter what you do, if you weld the top to the frame you WILL have warpage of the plate. It will bow and pull to where your put the welds... even if you try to put the smallest tack welds possible. The best way to attach a top is with bolts to pull it flat to a flat frame. It just can not be tacked to a frame and stay flat, just won't happen. The only somewhat success I've had with thin tables has been making a frame with the legs and making a duplicate frame for the top plate and tacking on the inside of the frame to the table top with as few tiny tacks as possible the put that frame onto the other frame and they seemed to smooth each other out flat. But this doubles up the material, work, etc....
Another thing... how are you welding mig(fast) or tig (slow).... when you weld fast and jump around the weld joint seem to pull against each other at the same pace but when you tig weld you tend to go much slower allowing the warpage to sink in deeper so possible preheating the other joints would simulate the heat of welding on the joints waiting to be welded..... I am uncertain this would help but it might... I would definitely try to weld as fast as you can.
I forgot about the grinding trick. Great point JD! We do a lot of doors and guarding at work. Knowing they want the welds ground smooth, I'll weld the top while clamped, quickly grind them flush while they are still hot, flip it, clamp it, weld out the back and corners. It has an added benefit of allowing the door to lay flat on the table after you flip. Works like a charm.
Never thought about "welding after welding". I'm always learning something new from you bud.