Welding thick top to base...

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I need to weld a 1/2" 32" x 48" piece of plate steel to a table base I built.  The base is constructed from 1 1/4" square.  I have a Lincoln 135SP MIG setup and am running flux core.This is going to be my primary welding table, so I want the top to be attached well so I don't get any deflection if I tack to it, etc..  First, what settings do I need to use for this?  Secondly, do I need to weld the top on both sides of the tube to ensure there's no buckling, etc..?Thanks!
Reply:I think with that 135 you'll want to run it at its max capacity to have a hope of fusing the 1/2" to the 1-1/4".  You'll be there till next year if you want to fill the entire 1/2" with fillet weld (i.e. if the plate is sitting on top of the frame with the vertical edges set back a bit from the vertical edges of the frame); if you're arranging it so that the plate sits inside the tube frame and flush with the top then you'll have no problems filling the small butt weld between (beveling the edges would help you fill it right in, but beads that just fuse the tops would work well).If it IS sitting with the vertical edges of the plate flush with the frame, you can run a butt weld on the outside without too much hassle.  Make sure to weld in such a way as to control distortion - middle of each of the sides first (about 1" of weld) then the corners (about 1" again) and then split the difference with 1" of weld each (now you're looking at 8 welds of 1" each for this step) and I'd think that'd hold pretty well if it's adequately fused.MR
Reply:Thanks BlowinBreakers.  I'm actually situating the top so that there is about 2" of overhang on each side of the table.  I plan on laying the top on the floor and flipping the table base on top of it and welding in that position.  Then I'll use my lift to get it sitting up right.In this situation, would you weld the top on both sides of the 1 1/4" tube or just along the outside edge?
Reply:I'd put fillet welds on the outside edges only if I was pressed for time, but I think it'd be just fine to wait for the plate to cool a bit (read: go have a beer or two) and come back and lay down some fillets on the inside edge.Sounds like it'll be a heck of a table.  I built a fab table with a 1/8" 4'x8' top and 2"x2"x1/8" ERW tubing as the legs/cross braces and 2"x2"x1/8" angle iron as the base for the top sheet's edges.  Worked out quite well to assemble it the way you've described - sheet on the garage floor, build the frame outline, weld in crossbracing, weld on legs (including plates and leveling bolts in the bottoms of each leg, since my garage floor is cracked and generally brutal... rental house, probably 60's built), then flip the whole mess over.I wish I had a lift... damn table probably weighed 400lbs, and that's being conservative.  Thank GOD for my football and weightlifting background, that's all I'll say about that.Good luck!MR
Reply:Well, I won't be pushed for time, so I will do it right and weld both sides.I put adjustable feet on my table as well.  I figured the chances of the floor being perfect was pretty slim.  Unfortunately, my shop is only 16x24 so I have to keep stuff pushed to the sides when not in use.  So being able to readjust the table's "levelness" is critical.  For smaller projects I will leave the table in against the wall.  I'm going to put the 4x8 sheets of concrete board on the shop walls  around it so I don't have to worry about setting anything on fire.Yeah, having the lift has been great.  I do a lot of small engine servicing/repair for family and friends and being able to lift a riding lawnmower up and working underneath it easily has been worth every penny of the cost of the I-Beam and trolley.  Of course, I put jack stands underneath to ensure it doesn't fall on me
Reply:I hear ya on the lift, wic.I made a 3,600lb rated gantry crane (complete with 4 swivel casters) for my (now ex) gf's dad, to help with his project of restoring a '64 Benz 230SL roadster... beautiful piece of work, if I do say so myself, but problem is that I delivered it to him - painted and all - about 10 days before the breakup.  2 1/2 years together, and she finally pushed me just enough to make me leave.Good thing Papa Bear paid for the steel in advance!   At any rate, I assembled and tested everything in my small shop, and the thing worked like a dream.  If you put it on appropriate jackstands instead of the casters, the beam and tube frame will lift 8k+ easy... but 2,000lb rated casters were more than 3x the price of the 900lb'ers I ended up putting on there.  And really, is the guy going to need to lift more than a ton and a half in a single go?  Hell, that crane would pick up the entire roadster if you rigged it right.Sounds like you're about to have a pretty darn sweet welding table, my friend.  Just a thought if you're looking for easy mobility and have a bit of extra budget to work with - hit up your local hardware store and grab some swing-away drop leg jacks with casters, designed for trailer leveling.  Put one on each corner such that you can swing them up when using the table and put them down and crank the jack up when you want to move it - hell, the savings on lift time (or your back/floor if you plan to just slide it) will be worth it in no time.MR
Reply:I have built a few tables similar to what your doing and I did weld both the inside and outside edges of the tube frame. On the 3/4" table top I used there was no problem with warping. I would suggest skipping around a little instead of starting at one end and going all the way around the frame. Attached ImagesLast edited by Robby T.; 10-08-2005 at 12:10 AM.