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  1. #1
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Posts
    128

    Default Flattening 16mm steel plate for a welding table

    Hi all - Happy New Year !!

    I've been given a 1200x600x16mm piece of scrap plate to use as the top for a small welding table, but turns out it has a bit of a bow in it.
    Approx 4mm if I put a straightedge across it.

    What is the easiest way to get one side relatively flat? My first thought is to just go at it with the angle grinder (in which case would it be better to remove the center from the convex side or the edges from the concave one??).
    My other thought was that I might be able to get some of the bow out by running some decent beads across the convex side with the MIG prior to using the grinder. Everything I weld seems to distort , but I don't know whether that size plate would get any useful movement.

    Any suggestions?

    Steve

  2. #2
    Join Date
    Feb 2013
    Location
    Laidley, SE Qld
    Posts
    755

    Default

    Easiest way to reduce the bow is to do as you suggest, i.e. run a bead across the underside. But just one at a time and not too heavy a bead, let it cool and see what improvement there is.

  3. #3
    Join Date
    Feb 2015
    Location
    Oz
    Age
    67
    Posts
    815

    Default

    I came across some stainless plate 7 or so years ago, nowhere near as big as yours but it too had a bow in in it. I made a frame from 2" RHS and then clamped the pate to the frame and tacked from the inside out. Seven years on it's still flat.

  4. #4
    BobL is online now Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    4,257

    Default

    I'm not saying this method is available to everyone but my BIL used to remove bends and bows using lengths of RSJ and the stabilising ft from a large crane/truck. It was interesting to watch him doing it - lots of length of hard wood, patience, and many small/incremental movements.

  5. #5
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Posts
    128

    Default

    Quote Originally Posted by BobL View Post
    I'm not saying this method is available to everyone but my BIL used to remove bends and bows using lengths of RSJ and the stabilising ft from a large crane/truck. It was interesting to watch him doing it - lots of length of hard wood, patience, and many small/incremental movements.
    Sadly I've no easy access to anything of sufficient size/mass to do similar with this bit of plate. Thinner ones have been fair game for driving over with my 4WD in the past, but its hard to get much more than a 1T on a point, and even 6mm tread plate takes a bit to move it permanently.
    I'll crank up the welder tonight and see how I go running some beads on this one...

    Steve

  6. #6
    Join Date
    Nov 2017
    Location
    Geelong, Australia
    Posts
    128

    Default

    Finally got a chance today to have a go at straightening the plate and making the table.
    Running the welds across to straighten it worked well. It only needs one reasonable bead across it to get a couple of mm movement over the 1200mm length, and I overcooked it slightly and had to run a light one on the other side of the plate to correct it.
    I've now got it to the point where the straightedge sits pretty nicely on it parallel with the edges, but there is still about 1mm twist diagonally across 2 of the corners. Good enough for my current purposes and I can mess with it more later if I find its causing issues.
    I forgot to take a photo when it was finished, but here's a progress shot of the table on its back after the main straightening was done.
    Ignore the lugs on the legs, they're nothing special. Legs are just some bits of scrap RHS I had and couldn't be bothered cutting the lugs off


    IMG_3902 (Medium).JPG

    Steve
    Attached Images Attached Images

  7. #7
    Join Date
    Sep 2011
    Location
    Emerald Central Qld
    Posts
    293

    Default

    I have used a large tip on the oxy heat up quick and hit the bend with a wet rag , the cooling will bow it back without welding a bead on one side.

    Yours looks good , have fun .

    Michael

  8. #8
    Join Date
    Apr 2008
    Location
    Perth
    Posts
    251

    Default

    I had the same problem when I bought a sheet of 12 mm plate to make my welding table. Had the seller cut a piece out for me in the size I wanted to fit the frame I had already made.

    I have two of those off road kangaroo jacks, turned the foot plate around an made two big jacking clamps. No probs, had my nephew weld the 12mm plate to the stand as he is a professional welder, left the clamps in place overnight. All was good, its level and thanks to them jacks I would have been stumped on trying to get the plate flat.

    DD

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