Fixing warped plate w/ holes (newbie questions)

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Hey All,I've wanted to learn how to weld for a long time so I ended up taking a welding class about a month back. Fast forward to now and I have an O/A setup and am in the progress of getting ready to start doing my own stuff at home. (I chose O/A first because it's versatile and I've heard that learning on O/A can help make you a better welder in general. I may get a MIG in the future, but for now I'll learn with the O/A).Anyways, the first step to outfitting my work area is to get a suitable surface, so last weekend I picked up a piece of approx. 3'x4'  3/8" plate to be the top of my table. The first problem is that it has a number of holes in it from where rivet presses were attached, and secondly the plate has a pretty big warp to it.First, fixing the holes. The holes are all 3/8", and I just happen to have some 3/8" rod that I figured I could cut, place in the holes, then weld them into the plate and grind it down after. The issue I'm thinking I have, though, is that I'm not sure my O/A torch will be up to the job. I only have a 75cf acetylene tank, which using the 1/7 rule limits me to just under 11cfm. Looking at a chart for my torch (Smith WH100), that limits me to something capable of only about 3/16". Will this indeed be an issue? Seeing as the patched holes don't really need to be uber strong, would a smaller tip make a "just under the surface weld" that would still be fine? I could weld from both sides, too.Second, the surface is warped a decent amount. When sitting on a flat ground, the middle of the plate is sitting about half an inch...maybe more...off the ground. Will there be ANY way for me to flatten this myself? It doesn't need to be super flat, but just a bit MORE flat would be nice. If I just put some bar under then ends and parked a 6500lb conversion van on it for a while, would that do anything or would it just bounce back up? I've heard using heat would do the trick, but again the 75cf acetylene tank doesn't allow for much output...and not only that I have no experience so I'd definitely screw it up. Alternatively, I had considered that maybe I could weld a few bolts onto the bottom of the plate so that when it's put onto a table frame I could just wrench down the bolts and flatten the top...would that be possible (and again, would I have any way of welding those bolts on with my small setup)?I'm new not only to welding, but also metalwork in general, so I'm open to any information that is given to me.Thanks! - Ian
Reply:Of the available methods, I'd probably suggest the vehicle and blocks 1st. I've straightened out tailgates and so on simply by sticking a couple of 4x4's under each end and then leaning on the center with the bucket of a machine. I'd probably jack up the SUV and then put the plate under it on a couple of 2x4's and then let the tire down on it and see if it will bend enough that way. I'd guess you may need at least 2 or 3 2x's laid flat under the ends. You'll need to get it to go well past flat to get the bow out of the plate. You can always go a bit farther if needed on say a 2nd or 3rd pass, and if you go a bit too far, flip the plate and repeat. 2nd option would be to build a heavy sub frame and bolt it down to that. I wouldn't bother welding the bolts. You already have holes in the top, so why not just pick up some large counter sunk screws or bolts and make use of whats already there? You'd probably have to put a chamfer on the holes to get the bolts to sit flush. No big deal with a drill and a counter sink. Just take it in small stages.Not even sure you need to bother filling the holes. Lots of guys go thru the trouble of drilling holes in their tops. Holes will give you places that you can use to bolt down clamps and jigs to secure work and hold things in place. If the holes are big enough, you can pass claps thru the top and then put the screw ends back on. The vise grip drill press clamps are a useful item if you have holes in your top. Clamping things so they don't move will allow you to use both hands with OA.If you feel you MUST fill the holes, I'd leave the plugs a bit short and then weld over them that way. You don't need full pen welds. If the plug is held down about an 1/8" or so below the surface, I'm betting you can run a bead around the top edge and then fill the center with no issues with what you have. If nothing else, preheat the area with the torch for a bit to get everything red before you weld. Also it is possible to slightly exceed the 1/7th rule if you just do it for a short period of time and then let the cylinder sit to "recover". I wouldn't go crazy, but stepping up one tip size for a few minutes or so wouldn't end the world..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:How do the holes line up in the plate?  I guess what I'm asking is, can you bolt it to an I-beam or piece of channel to flatten it out?  Why fill the holes?  Get yourself some Bridgeport hold down clamps with the 3/8" sized hardware.  They'll be more useful than you could ever imagine.  These may even work:
Reply:Thanks for the tips guy. I admit I hadn't thought about using the holes for clamps, but even still I think I'd rather fill in at least some of them since they seem to be in weird spots. I've attached a picture of both the holes and the warp in the plate.I think I'll try the "drop the van" thing on it tomorrow to try and get rid of the warp once I get some help to move it around... Attached Images
Reply:Build a frame under the plate and that will flatten it out nicely. Buy some 4" channel and build a box frame with a strut or 2 in the middle. This will make it sturdy and always straight and flat. If you dont, you will wish you did.CERTIFICATIONS:7018M- H.V.O10718M- H.V.O11018M- H.V.O9N10- H.V.O71T-1-HYM- H.O.V100S1 PULSE ARC 0,035- H.O.V100S1 PULSE ARC 0.045- H.O.VER70S-3 PULSE ARC 0.035 H.O.VER70S-3 PULSE ARC 0.045 H.O.VER5554- H.O.V
Reply:I'd leave the holes. They'll come in handy since you can consider them when clamping and jigging.
Reply:Even though those holes are right on the edges, I'd still leave them.  They won't ever cause you a problem.  Look at the Acorn tables and how half the surface is holes.  If you are just looking for a project, well, that's something else entirely.  But realistically, they're no problem.Try to get 'er flattened out and go from there.  Add your location to your profile while you're at it.
Reply:Leave the holes.   It looks to me that one or more edges are flame cut and the other edges are sheared or a rolled mill edge?  The flame cutting might have cause the bulge.   Easiest would be to tack weld some 3/8 by 3 inch flat bar on edge to the bottom but you need an arc weld to do it fast .... and some wedges and dogs.
Reply:Originally Posted by NHMattBuild a frame under the plate and that will flatten it out nicely. Buy some 4" channel and build a box frame with a strut or 2 in the middle. This will make it sturdy and always straight and flat. If you dont, you will wish you did.
Reply:You could tack the plate, or you could simply use counter sunk bolts and either drill and tap the channel or use nuts on the bottom. Depending how stiff that wooden bench frame is, you might be able to clamp down the center and run heavy counter sunk screws in every 2 or 3" and have that work as well. If the wood frame bows a bit, you could reinforce it with the channel or a piece of flat stock. I know it's not "welding" but with limited tools, some times the simple solutions are best..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by ian1386I had to look up what wedges and dogs are, and I *think* I know what you mean...use the dogs to pull the bar and the plate together as you tack weld across it, right? An arc would definitely be faster, but I do have time...might not be a bad idea.
Reply:if you use the van trick, set it down a little at a time to apply the downward pressure then rap the plate with a 3lb single jack or such hammer half a dozen times at various points that the van isn't covering and add a little more pressure til you get it straight. the hammer will relieve the stress and realign the molecules so the bow in the plate will hold what you have taken out each time. works like a charm.225NT bobcatAEAD200LEScott 125mm175, mm252 w 30A, PT225mm211, TA 181iHyper Therm 380, cut master 529100X & XX, Digital Elite6 Victor setssmith little torch, meco midget kalamazoo band sawsteel max saw evoulution circular saw
Reply:the day you fill those holes will be the day you figure out a use for them, they are perefct for holddown clamps..you can make some that work like the one in post 3 by cutting a c clamp and welding on a threaded rod.. stick it through the hole and catch it under the table with a wingnut...
Reply:Originally Posted by ian1386 An arc would definitely be faster, but I do have time...might not be a bad idea.
Reply:Originally Posted by jmtebbensLet me clarify.  Heat is what probably bent your plate.  An arc welder creates an instant burn, fries for a couple seconds, and then it's done.  An O/A rig takes much longer to develop your puddle and then manually add the filler.  You want to minimize the amount of heat you put to the plate to prevent more distortion.  That is where the speed of the arc welder becomes important.