Taking the bend out of 1/4 steel plate

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Hi. This is my first post to the forum. I'm making a round table that will have a steel support system on the underside. I'm having 1/4" steel plate water-jet cut to the pattern on my diagram. I'm expecting that the cut plate will have some sort of deflection over the 5 foot diameter. I plan on stiffening the plate with 5 pieces of 1/4" (T) x 3/4" (W) flat bar forming a "t" joint. These five pieces will follow the pentagon pattern all meeting in the center of the circle.Will the 3/4" strips be enough to keep the plate flat and remove any expected deflection ?. I don't have room to make these stiffener strips any wider as they will be too visible (maybe 1" max).Also when welding "T" stiffener strips do you weld on the concave or convex side of the plate that shows deflection ?Hope my description is understandable and many thanks for any comments in advance..... Steven Attached Images
Reply:Steven, nice job on the CAD drawing.  Obviously you've thought about this for awhile.I'm missing the big picture. You've got a steel top table that you want to re-inforce.  What's holding the table up... a single center post, four posts in a square, three posts?  I'd almost recommend an angle iron or hollow box beam oriented to the support post structure.  If you've got a four legged table, you would create a square support structure.   If you are really worried, and need to have perfect support, I'd bend a support beam into a 360 degree circle, with a diameter 15% smaller than the outer diameter of your table top.  Add spokes to the inside of the circle as needed.  I'm not sure the star shape you've shown will really get to where you want to go, unless you are planning a single cylinder post support (like the wobbly tables I see in the cafeteria around here...)--zipLast edited by zipzit; 03-01-2012 at 02:42 PM.
Reply:Hi Zip... thanks for the reply.Yes there will be a single heavy concrete pedestal base. This steel structure will then be bolted to the concrete in the center (16" diameter base I got the wobbly part under control  ). I will then be adding some wood to the top of the steel.The wood top will be 5' diameter with this steel structure slightly inset below.My main concern is dealing with the potential deflection after I get the steel "star shape" water-jet cut. The plan is to add the 3/4" stiffeners to take any deflection out as well as add some additional structural strength overall. So basically will 3/4" be enough to accomplish this and if there is deflection is it good pratice to weld the stiffeners on the concave or convex side of a deflected plate ?Many thanks for reading and helping.
Reply:I'm not sure I get the deflection worry.  Water jet is unlike laser, plasma or gas cutting.There is no heat so there is no warpage or deflection.  The piece you cut out with a water jet will be as flat as the piece you cut it out of.  Or are you talking about something else???
Reply:How thick is the wood top going to be, and what's the intended use of the table? What's the purpose of using the plate at all in the first place?I'm FAR from experienced, but if I were making what I'm picturing I'd probably take a different approach. For instance, if you're pouring the concrete pillar yourself, can you not use that to your advantage to avoid the plate? What I have in mind is this: 1) Make an X out of some channel so that it's 5' wide in each direction. 2) On the non-flat side of this X, weld some rebar or something bent into U shapes so that they protrude downwards by a foot or so. 3) When you pour the concrete, embed the X into the concrete by inserting the U's i into the form and filling around it. When the top of the concrete is flattened out, do it so that it's flush with the top of the angle. Make sure the X is level (relative to the pillar). 4) Drill holes into the angle, screw on wood top, done.This would involve less materials and would involve very little welding.If you want the support to be removable, you could still do it by just having the bolts embedded into the concrete and using some spacers to bolt the X onto the concrete (leaving a gap the width of the bottom of the angle).Am I missing a good reason for having the plate?Last edited by ian1386; 03-01-2012 at 08:31 PM.
Reply:the more stiffeners you weld to it the more its gonna warp..bfh..
Reply:Welding to either the underside or top of the plate will cause distortion.  It's unavoidable.To minimize distortion you have to stitch weld.  Small welds an inch or less in length every 3-6 inches.  Skip around on the structure welding in different areas, don't do a bunch of welds in the same area, let the weld area cool before adding any more material there.This isn't structural, so you don't need a bunch of welds to hold the plate in place.  SMALL WELDS.  Welding on top of the plate, or on the underside, will cause the same amount of distortion.  Due to the design you can't even out the distortion by welding in identical places on either side of the plate, the welds wouldn't line up due to the T brace and the actual joint on the top side.Unless you own a really large propane heating tip, stress relief is gonna be hard.  You will live with what you get.  So limit the heat by doing SMALL WELDS.Did I say to use SMALL WELDS??"Any day above ground is a good day"http://www.farmersamm.com/
Reply:And why in Gods Name are you using 1/4 plate???????????"Any day above ground is a good day"http://www.farmersamm.com/
Reply:ok...small welds yes.. got it.1/4 plate because the inner circle of the plate will have some through hex bolts for level adjusters to hold a 30" diameter piece of concrete. This center piece of concrete will be surrounded by 1 1/4" thick wood 15" Wide of wood for plates etc....the 5 steel sticks protruding from the center circle of steel will hold the wood element.... clear as mud ?is the 1/4 inch plate overkill. Do you think 1/8" with the stiffeners will work ?. I don't think the cost will be substantially different so went for the thicker option thinking it would be stronger and more flat after cutting.
Reply:here's a pic of the final table.. maybe this will help in understanding the steel structure I think will work. Attached Images
Reply:thank you
Reply:Originally Posted by stevenvancouverhere's a pic of the final table.. maybe this will help in understanding the steel structure I think will work.
Reply:Another route you might go.Considering the pedestal will support most of the steel weight, and the only cantilevered load will be the lighter wood, it might just pay to use square tubing for the under-table supports and simply use a good construction adhesive to cement the steel center to the frame.The frame is the real support for the whole tabletop.  Square tubing as light as 14ga would do a fine job of supporting the table top, unless you want to use heavier 11ga.  Square tubing has the advantage of two webs instead of the single web available in the T supports.  Top and lower flanges are more robust too (and you'd HAVE a bottom flange).Using two halves for the center, instead of the pie shaped pieces, would go a long way to alleviate distortion if you do decide to weld it up.  Very often you can just put a few tack like welds on the perimeter and it'll hold just fine.  Gravity goes a long way in this type of project.  The entire top on my welding table (3/16 plate) is tacked in place, and it does very well because support is provided by the frame."Any day above ground is a good day"http://www.farmersamm.com/
Reply:I think I'd ditch the plate all together.  Go with five (or more) angle iron spokes attached to some sort of hub for mounting to the pedestal.  Set your concrete slab in the center with a few shims and construction adhesive.  Screw the wood from the underside.  The only welds on the thing would be from spokes to pedestal hub.My name's not Jim....
Reply:Not sure you even need metal for this projectPedestalOn top of that a Plywood disc the diameter of where your steel supports would be and  secured to the pedestal with epoxy/ construction adhesive and counter sunk screwsThen place your Finished wood top on that- secure it to the Plywood from underneathThen your  Concrete center piece set in place with construction adhesiveEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:The steel center is artistic!!!!!!!!!!!!!!!!!!!!!!  Have you no sense of style????"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by farmersammThe steel center is artistic!!!!!!!!!!!!!!!!!!!!!!  Have you no sense of style????
Reply:Originally Posted by stevenvancouverok...small welds yes.. got it.1/4 plate because the inner circle of the plate will have some through hex bolts for level adjusters to hold a 30" diameter piece of concrete. This center piece of concrete will be surrounded by 1 1/4" thick wood 15" Wide of wood for plates etc....the 5 steel sticks protruding from the center circle of steel will hold the wood element.... clear as mud ?is the 1/4 inch plate overkill. Do you think 1/8" with the stiffeners will work ?. I don't think the cost will be substantially different so went for the thicker option thinking it would be stronger and more flat after cutting.
Reply:Originally Posted by stevenvancouverHi Zip... thanks for the reply.Yes there will be a single heavy concrete pedestal base. This steel structure will then be bolted to the concrete in the center (16" diameter base I got the wobbly part under control  ). I will then be adding some wood to the top of the steel.The wood top will be 5' diameter with this steel structure slightly inset below.My main concern is dealing with the potential deflection after I get the steel "star shape" water-jet cut. The plan is to add the 3/4" stiffeners to take any deflection out as well as add some additional structural strength overall. So basically will 3/4" be enough to accomplish this and if there is deflection is it good pratice to weld the stiffeners on the concave or convex side of a deflected plate ?Many thanks for reading and helping.
Reply:Oh crap, you're right"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Sorry Steve, this has gotten out of hand, I apologize"Any day above ground is a good day"http://www.farmersamm.com/
Reply:Originally Posted by farmersammRead again Ed  Glasses maybe??
Reply:Originally Posted by farmersammSorry Steve, this has gotten out of hand, I apologize
Reply:So what In Gods Name do you even need any kind of thick plate for??Just enough to hold the concrete inset, without the concrete cracking, will be sufficient3/16 max, or expanded metal"Any day above ground is a good day"http://www.farmersamm.com/
Reply:expanded metal will at least hold the pieces from falling on yer feet if the concrete cracks"Any day above ground is a good day"http://www.farmersamm.com/Originally Posted by farmersammexpanded metal will at least hold the pieces from falling on yer feet if the concrete cracks
Reply:"My main concern is dealing with the potential deflection after I get the steel "star shape" water-jet cut."I think this is the whole reason for the thread so I'll ask, how much deflection are you expecting from the water jet process?
Reply:stefuel.... the deflection over a 5 foot span could have  1/16" arc ?..maybe not. It's my understanding that steel sheets start of in roll format when manufactured and there is a hidden memory of "spring". I could get lucky and there is noneSo...which side would you weld the stiffener strips to ?...the concave or convex and would a 3/4 inch strip be enough to take lock the piece in flat.I'm now thinking of retracting the large 30" diameter of plate down to 16" (diameter of concrete pedestal top) and welding 3/4" or 1" squaretube in the star pattern similar to the beginning of the thread. How strong would the 3/4" or 1" tube be cantilevered about 20" from edge of steel plate center ? Diagram attached Attached Images
Reply:Originally Posted by stevenvancouverHow strong would the 3/4" or 1" tube be cantilevered about 20" from edge of steel plate center ?
Reply:DSW...thanks. one of my goals is to keep the steel element as thin as possible (design aesthetic) but still strong enough for the application. I may cut the tips of the tube on an angle say 60 degrees to avoid the hard right angle.the Wood will be 1 1/4 " thick only.
Reply:Originally Posted by BoostinjdmI think I'd ditch the plate all together.  Go with five (or more) angle iron spokes attached to some sort of hub for mounting to the pedestal.  Set your concrete slab in the center with a few shims and construction adhesive.  Screw the wood from the underside.  The only welds on the thing would be from spokes to pedestal hub.
Reply:Originally Posted by StortsNice IDEA! And maybe a rolled ban to make the Old wagon wheel look!!!,,But thats only my option!! and It would give some more strenght,,But as you said, shims,and construction adhesive ,and you would be the ONLY person that knows! ,Jack
Reply:Originally Posted by stevenvancouveruntil they decide to move it one day and it can't be disassembled . No PL400 adhesive on this one. All bolts/nuts/screws/levellers.
Reply:Originally Posted by stevenvancouveruntil they decide to move it one day and it can't be disassembled . No PL400 adhesive on this one. All bolts/nuts/screws/levellers.
Reply:Originally Posted by Boostinjdm a concrete disk on top of a concrete pedestal would be too heavy to manhandle anyway so removal wouldn't be an issue.
Reply:thanks everyone for your feedback and injection of some humor. I have a good understanding of what to do now and will post pictures in the future of the final table.I really appreciate sites like this and the transfer of knowledge to help people. I also do woodwork and concrete which all requires a never ending process of learning through trial and error. Sometimes it's nice to avoid an error.my website is http://www.woodstonedesign.ca . I look forward to contributing to this forum if I can.Steven
Reply:I took a look at your site. Very nice work on the crete. I like a lot of the designs. I did a ton of stamping for quite a few years, and did a bit of work with another guy who's specializing in custom concrete countertops now. I'm guessing you probably do what he does, mix it up in the shop and pour it out, then grind and polish to get the finish you want.I might be doing a custom cast concrete headstone for the guy who I used to do the stamp work for. His wife was talking about getting a custom stamp done for his grave marker. I may PM you for some tips on finishing the sides and back. Suggestions on a good wet grinder, finishing grits for the diamond wheels, maybe some mix suggestions etc. I lost all my mix info on the counter top stuff. The guy who does the counter tops was originally going to get the work, but he stiffed them for a bunch of money and she won't deal with him again. I think she really wants us guys who used to work for her husband to do the work anyways. It's a shame I can't sculpt. I can make and pour the stamp myself since I used to pour custom stamps for a lot of the work we did, but making the master for the stamp is beyond my skill set to have it turn out the way I think she wants..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