How to create a flat table without a flat surface?

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I want to build a new welding table (5x10 out of at least 5/8" steel). How can I make sure the frame is flat for the top? My floor is composed of several cracked slabs of concrete angled in towards a drain, so I can't use that. Otherwise I have two 2x4 tables. I have like 20 of those small machinist jacks, I was thinking maybe resting the top of the table frame on the jacks and leveling it up with a machinist level, welding that, and then welding the legs on? Any other brilliant ideas?John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:Levelling the top then building the frame on it is probably your best option. But, don't just weld legs to the top. You should still have a frame supporting it so it doesn't sag over time.  I'm thinking at LEAST 2" square tubing with 1/4" wall thickness. I would go with 2.5 or 3" though.Also, you may want to have 6 legs instead of 4.Just my opinion...GravelThe difference between theory and practice is that in theory there is no difference.
Reply:What about, between the table top (with frame) and the legs you use some heavy threaded rod and nuts to make the legs adjustable. Kind of like how you level the settling in a log home. That way you can move the table around the shop and adjust it. Castors would make it even better, I might do that when I get around to making my own table.
Reply:Originally Posted by GravelLevelling the top then building the frame on it is probably your best option.
Reply:C'mon guys. Bolt the four corner plates to the floor where you'll begin. Take a nail in a wall and tie a string at about the height you want. level across with a water level and mark the other wall for a nail.String across. Measure down to the plate and cut leg one, plumb it and weld it to the plate.Move to the others.Build away. Don't be like the rest of these dorks and weld the damn top on .Just sit it on the channels(you ARE using c channel ? ) and get 6 fat boys to shove it in place.Not too fat. Even my old asczzz can lift 200 lbs of iron.Last edited by Burpee; 03-25-2014 at 05:22 AM.Reason: Asczzz muddafuhha !Bubble gumTooth pixDuct tapeBlack glueGBMF hammerScrew gun --bad battery (see above)
Reply:What are these devices you call a "nail" and a "string"? And this "water level" you speak of?  It is strange to me...
Reply:Originally Posted by RodJWhat are these devices you call a "nail" and a "string"? And this "water level" you speak of?  It is strange to me...
Reply:Use winding sticks to get the frame elements in the same plane.http://en.wikipedia.org/wiki/Winding_stick
Reply:Originally Posted by DSWGreat idea, but flipping a 1300+ lb table isn't for someone who doesn't have the right toys. My numbers put a  5x10 sheet of 5/8" at about 1275 lbs and we haven't added the base and legs yet. My big table weighs a bit more than that and moving it was a challenge even with the use of heavy equipment.Depending on what he has available to move something of this weight, I'd be tempted to just use jacks or saw horses to level the subfame and then add the legs and bracing to that. Even the base may be too heavy to easily flip. He may have to build down from the sub frame vs building up. Not all that tough if it's built in position so the legs can be cut to length or installed after the levelers are added to the lower end.Levelers are a good suggestion, but with the weight of the  table, he may have to use a jack to lift the table so he can turn threaded rods, I'd look for large acme threaded rod vs standard threads if he can for this. Weight of the table may preclude moving it very much, especially if the floor isn't smooth so you can't use wheels. I have access to a laser level, so that's what I'd use myself. Lacking this my next thought would be a simple water level using some clear tube, some water and some food coloring to make the water easier to see. It's almost as dead accurate as a laser over short distances if you take your time. Next would be my 6' stablia level. Problem with smaller levels is if your frame members aren't dead straight themselves, a bow in the material may give you a false read. Where you set the level may be nice, but you won't get all 4 corners even. That's the nice thing about a laser or water level. You get a constant reference you can use anywhere on the frame to determine if the unit is level. I've seen plenty of guys over the years use short 2' levels and think they got things level when all they did was make 5 or 6 sections all parallel with each other at different heights.
Reply:Originally Posted by BurpeeC'mon guys. Bolt the four corner plates to the floor where you'll begin. Take a nail in a wall and tie a string at about the height you want. level across with a water level and mark the other wall for a nail.String across. Measure down to the plate and cut leg one, plumb it and weld it to the plate.Move to the others.Build away. Don't be like the rest of these dorks and weld the damn top on .Just sit it on the channels(you ARE using c channel ? ) and get 6 fat boys to shove it in place.Not too fat. Even my old asczzz can lift 200 lbs of iron.
Reply:a water level would help.  I would imagine final level would be achieved with leveler in the legs.
Reply:Get a ply wood or particle board  and shim the sheet to flat.  level is nicer, but flat will do and build your frame on it, I would weld some 3/4 to 1"  nuts on the bottom of the legs, and then use a short  bolt for levelers,  when you get the frame made it move to floor, put top on and if top needs a shim her or there use them,  one of the handiest tools I have in building some thing is a few small wedges, one day I needed about 10 degree angle off of some 1/2" by 4" flat and there is some small wedges as drop and they will work wonders to line up things and to adjust a weld or what ever drive in tack remove the wedge  and  move on,(if one has a flat bed truck or trailer, one could most likely put some leveling jacks on each corner and use it, and if one has a bunch of short scrap to use as shim shock one can most like lay out the main under part of the table and shim them flat and level, tack and if any out of square tap it square and or use the warp of the welds to pull it back into square  once you have the main part square and flat welding legs on and cross supports should not be that hard, one can flip and move it so most of your welds are flat welds.Last edited by Farmerboy; 03-27-2014 at 11:11 AM.
Reply:My table has casters, which I highly recommend, I move it around about once a week. So, I can't easily bolt it to the floor, to make it flat, I had to rely on the frame. When I made my table I built the frame first. IMHO the frame needs to be strong enough to hold the sheet flat. You can't rely on the sheet being perfectly flat, unless you actually go down to steel yard and pick out a flat one (good luck sorting through sheets that weigh 1/2 ton without a very patient forklift driver). And another reason for a strong frame, is if you ever apply heat, unevenly, to the table, it might warp, if the frame isn't strong enough. The frame on mine is 2x6x.120 tube, and the top is 1/2" (I wish I had gone with 5/8"). Here's my procedure:1. Set up the parts, level as you can.2. Tack up the table frame.3. Level everything you can.4. Weld it up.5. Straighten any of the frame members that may have warped, using heat shrinking.6. To check for twist, Run strings, X wise, from corner to corner, tight as possible, with spacers (of known thicknesses) under the strings at the corners of the table frame so the strings don't touch the frame or each other.Measure the distance between the strings at the center and adjust the frame by heat shrinking till the spacing is right.7. Put on the top.Last edited by fortyonethirty; 03-27-2014 at 11:31 AM.Ian TannerKawasaki KX450 and many other fine tools
Reply:Originally Posted by RodJWhat are these devices you call a "nail" and a "string"? And this "water level" you speak of?  It is strange to me...
Reply:Glad to see I'm not the only one left that uses a water level!!Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:Lazerz my ascz Bubble gumTooth pixDuct tapeBlack glueGBMF hammerScrew gun --bad battery (see above)
Reply:the machinist answer would be to make three flatish surfaces. flip 2 upside down on 1. mark interference points with dye. Scrape 1. turn 2 90 deg and repeat. do the same for 1 on two,  1 on 3, 3 on 1, 3 on two,  and two on 3 and you will end up with three perfectly flat surfaces.