Industrial strength workbenches

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I am getting ready to build my heavy duty workbenches (two of them) and I wanted some advice.  I all ready have the bench top steel plates they are both 10' long by 30" deep by 1 1/2" thick.  I got the plate for free while working on a jobsite, so don't say they are too thick!  My question to you guys is what size legs do you think I should go with?  My brother and I were talking yesterday and he thinks I can go with 3" x 3" x 3/16" square tubing.  I want to go with 4x4x1/4" what do you guys think?  Cost is not a big problem, the 24 foot piece is $125 delivered for the 3" and $175 for the 4".  The bench tops weigh in at 1500 pounds.  Next question, how many legs?  We discussed only four, then six, then we talked about 5.  I like the idea of five, but is it going to do enough having only one leg in the middle of the back?  I am not making a frame, the legs are getting either welded right to the bench or the will have a flange that will bolt them to it.  I am leaning towards the flange idea.  Well, what do you guys think?  Any suggestions?  Thanks!
Reply:I think the five legs would be fine. I would lean towards the 4 x 4 x 1/4 and I would put the fifth leg in the middle lenghtwise and widthwise. That should eliminate any possibility of sagging in the front which I don't think is possible. I would also put adjusters on all legs. Just my opinion.
Reply:Please tell me where I sign up for the Free 10'x30"x1.5".I think 4 legs will be fine, is there any specific reason why you don't want to make a frame?
Reply:Originally Posted by Eric NPlease tell me where I sign up for the Free 10'x30"x1.5".
Reply:Originally Posted by StroutyI am getting ready to build my heavy duty workbenches (two of them) and I wanted some advice.  I all ready have the bench top steel plates they are both 10' long by 30" deep by 1 1/2" thick. . . .. . .As far as a frame, I have some gladiator carts that I need to be able to roll underneath it when not in use.  I don't feel that I need a frame for the top, I will install braces to tie all the legs together, but those will be towards the bottom.
Reply:My tax dollars at work.  Well, at least the money will end up going toward something useful.I'm not really qualified to give advice, but since I helped pay for it...  With the supporting structure, I think your biggest issue is the weight of the bench itself (sort of like the weight of cars being negligible on a highway bridge).  Either 3" or 4" tubing would bear the weight fine, but you're going to want a lot of lateral strength (a stonehenge type arrangement is more vulnerable to force from the side than force from above).  I'd do some diagonals both on the back and on the sides.I think your biggest issue with the top is the small incremental movements from something like repeated hammer blows.  To that end, you only need to arrest each tiny movement.  You could weld in L-shaped tabs to the legs and then drill and tap holes that extend up without breaking the surface.  If you have a mag drill, then use it -- but mild steel is easy to drill is you have a low-speed drill.  I have a 1" thick top for one of my benches and I added holes for a vise with a cheap Harbor Freight low-RPM drill and equally-cheap Harbor Freight bits.  It went through it like butter, and the bits look like they could do 50 more holes without any issue. What kind of work are you planning for the bench?Jack OlsenMy garage website
Reply:Originally Posted by Jack OlsenIf you have a mag drill, then use it -- but mild steel is easy to drill is you have a low-speed drill.  I have a 1" thick top for one of my benches and I added holes for a vise with a cheap Harbor Freight low-RPM drill and equally-cheap Harbor Freight bits.  It went through it like butter, and the bits look like they could do 50 more holes without any issues.
Reply:HEY! I WANT MY BENCH BACK!  Sounds almost exactly like mine. I think the legs are 4" but I forget right now. There are 6 legs, the center 2 don't show well in the pict I have on the computer. My top is about 12' long  32" wide  and 1 1/2" thick. It also looks like at one time someone either cut the plate in half or sliced off part along the back edge.Never had any problems with the legs and weight. We had our 900 lb bucket on it no problem, and even the 2 ton plow for the Mack on there one time trying to straighten it. Table worked great to help restraighten a bucket some knuckle head bent the floor out of. We jsut mounted it on the track hoe after we bought it and rolled it against the top to straighten it while we added a bit of heat before rewelding. Attached ImagesLast edited by DSW; 06-08-2010 at 10:10 PM..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 denrepI think that a 10' bench with just a light tin top like this needs a frame, or at least welded strong-backs.Good Luck
Reply:Originally Posted by Denrep  I think that a 10' bench with just a light tin top like this needs a frame, or at least welded strong-backs.
Reply:I would never think it would sag, I will use 6 posts so it won't ever be an issue.
Reply:With legs in the center sag wouldn't be an issue, but it'd still be better to have a frame.No, you wouldn't think that thick steel would sag very easy, but some time watch the deflection of a forklift tine, even with a very light load.Anyway, I'll post my entry for the "take that fight outside" super-bench review. Attachment 51988Last edited by denrep; 10-19-2010 at 11:45 PM.
Reply:That's too thick.  Since I payed for it, I'd be willing to take it off your hands.  Only if you'll deliver though...My name's not Jim....
Reply:denreps got it right here, the old iron layout/inspection tables were quite thick and had robust webbing in the casting. They still had jack screws on legs underneath pointing up to the table at 2 foot spacing.Matt
Reply:Couple of months ago a guy on CL was offering 3  10' by 20' by 3" plates at under scrap price if you could load and haul them. I didn't get there soon enough. I wept for days.tractor,loader.dozer,backhoe,and all the tools to keep em movin