Welding table

Trying to build a welding bench. Bought a bit of steel, 5mm x 500mm x 300 mm, which is big enough for my needs - but it is curved, about 4mm
in the center of the long direction, and I need it flat.
Is this curve normal/acceptable? Should I return the steel?
Any idea how to straighten it? I jumped up and down on it, suspended at the ends, without effect.
ta,
-- Peter Fairbrother
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On Thu, 27 Aug 2015 11:39:00 +0100, Peter Fairbrother

Greetings Peter, Look up flame straightening. If you have a torch you can use it to straighten your plate pretty easily. See this link: http://www.boconline.co.uk/internet.lg.lg.gbr/en/images/Fundamentals-of-Flame-Straightening410_113398.pdf It has all the info you need for flame straightening. Eric
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On 27/08/15 17:13, snipped-for-privacy@whidbey.com wrote:

Thanks, that looks interesting - but I suspect the learning curve is likely to be steep and long. Something for another day, perhaps.
I am thinking about welding a couple of lengths of box section to the bottom - I was planning on this anyway, but maybe now I will make the box sections a little deeper and thicker.
Any other suggestions?
-- Peter F
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On 28/08/2015 7:39 PM, Peter Fairbrother wrote:

Tack weld your box section along the plate 90 deg to the bow at one end only make some dog leg pieces like an L weld the L upside down to the plate so the short leg is over the box section and there is a gap between the L and the box section . Then get steel wedges and drive beween the dog and the box section and it should pull the plate down to the box section . Just move one dog leg at a time progressing from the the last weld removing the wedge and knocking it under the next dog leg weld and so forth .
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On 02/09/15 10:23, Bluey69 wrote:

Ah is this L-piece like a clamp? I can just clamp it.
What I am planning to do is to weld one end of two 60x40x3x480 box sections at 90 deg to the bow, on top of the plate with the bow up, put two 0.5mm shims in the middle, then clamp the other ends and check for flatness.
If all goes well, then weld weld weld. If not, adjust shims, try again.
The shim is calculated so that it will take 500N to bend the box sections that much, so putting 1000N on the plate, which is about what is needed to elastically straighten it.
-- Peter Fairbrother
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On 3/09/2015 1:38 AM, Peter Fairbrother wrote:

the" L " shape is a cleat or dog , the wedge is driven between the cleat and the box sectionwhich pulls the plate down tight on the box .
I recntly built a welding table myself ,I used 3 mm black steel plate for the top and used this method the pull the plate down tight on the frame so I didnt have a wave top table after welding . My table is 1.2metrs wide and 2.4 meters long ( Full sheet of plate) I started welding down the centre frame each side weld alternate to each other and worked my way out to the frame edges so as not to create a buckled metal table top. I knocked the cleats off and ground off the welds after I finished welding the top to the frame.Not that it really mattered they were all underside of the top out of sight ,but Im a neat person and Like things to be tidy .
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if you planned this just go ahead with the boxstrips, however watch the sequence of welding as this will have effect on the straightness of your plate. It is very common to straighten plates even very big ones of the hull of a ship. you could also drive with a car over the plate (with one side on a piece of wood) to straighten it. when you use the table it will also bend due to the temperatures used.
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wrote:

As others have said, if is's just a bend and not domed then clamping and welding will work. But I'd tend to take the piece back unless it was sold as used or scrap etc. A piece that size, sheared from sheet should come out flat if done properly. If the suppliers can't sheer it flat, they can plasma cut it or roll it afterwards...
--

Mark Rand
RTFM

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