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  • Questions for First Time Shaping Flat Bar

    Hey all,

    So I have taken up some simple furniture making as a hobby, I have always used wood in the past to make everything, including legs. This time, I wanted to try my hand at shaping flat bar for desk legs. The shape I was going for is this:



    I need the metal to be 8ft long in order to complete it with one piece, and the only type found at my local Home Depot or Lowe's Home Improvement is 1/8in - 8-ft x 2-in Aluminum Metal Flat Bar (http://www.lowes.com/pd/Steelworks-8...at-Bar/3058163). All other types of metal they have comes in much smaller pieces and I am not sure where else to find it. I was planning on putting it on a clamp and hammering it into shape while cold.

    My questions are:

    1) is Aluminum good for this application? I was told it may rip or even break.
    2) is that the best method to shape it?
    3) is 1/8 thick strong enough for this application?

    Thanks for any and all help!

  • #2
    I assume the legs are used in the same position as shown, the horizontal section being the bottom.

    Originally posted by Aquesada001 View Post
    Hey all,

    So I have taken up some simple furniture making as a hobby, I have always used wood in the past to make everything, including legs. This time, I wanted to try my hand at shaping flat bar for desk legs. The shape I was going for is this:

    I need the metal to be 8ft long in order to complete it with one piece, and the only type found at my local Home Depot or Lowe's Home Improvement is 1/8in - 8-ft x 2-in Aluminum Metal Flat Bar (http://www.lowes.com/pd/Steelworks-8...at-Bar/3058163). All other types of metal they have comes in much smaller pieces and I am not sure where else to find it. I was planning on putting it on a clamp and hammering it into shape while cold.

    My questions are:

    1) is Aluminum good for this application? I was told it may rip or even break.
    It could be weakened significantly by sharp bends, especially if it is rolled sheet bent along the rolling direction. The strips you refer to are generally extruded, and may not be a particularly formable alloy, and may not respond well to the sharp bends. Cut strips from rolled sheet would likely be better.


    Originally posted by Aquesada001 View Post
    2) is that the best method to shape it?
    Hammering will not make a clean bend, particularly in aluminum.


    Originally posted by Aquesada001 View Post
    3) is 1/8 thick strong enough for this application?

    Thanks for any and all help!
    1/8" aluminum is somewhat floppy, and not as stiff as similar steel. You need about 1.5x the thickness for equal stiffness. I'd not suppose it would be good
    CNC machines only go through the motions.

    Ideas expressed may be mine, or from anyone else in the universe.
    Not responsible for clerical errors. Or those made by lay people either.
    Number formats and units may be chosen at random depending on what day it is.
    I reserve the right to use a number system with any integer base without prior notice.
    Generalizations are understood to be "often" true, but not true in every case.

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    • #3
      The LAST place you want to buy stock sizes in steel or aluminum from is the Big Box. Buy instead from a local steel supplier for about half the price per unit. Structural shapes (angles, flats, I beams etc) come in 20 or 40 ft lengths with 20 being typical for smaller sizes. They will cut to length but may have a minimum order. Have your requirements ready in a list so as not to waste the counterman's time.

      There are steel supply yards that specialize in selling in small quantities to walk-in customers. They are a little more expensive but you're paying for convenience. I live 40 miles from a full service commercial steel yard but I have a local welding supply whose small steel yard has overtaken the welding side in volume. They stock most common structural shapes and sizes but can bring in whatever I need in a day like thick walled tube, alloy steel, etc.

      Steel flat bar is springy in the flat direction. When used un-braced as table legs for instance, you can expect the table to sway and wobble in response to every small bump and nudge. I suggest you triangulate your legs in some clever artistic way.
      Last edited by Forrest Addy; 07-28-2016, 11:23 AM.

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      • #4
        Those legs are not formed out of one piece. The top pieces where the tabletop would bolt to look to be welded (noticed how they have been ground and you can just make out the fillet). This is because the radius of that bend is so sharp; it would likely result in breaking the steel. Aluminum? No chance.

        You can form something like this out of one piece but you're not going to be able to get that sharp angle at the top. There will have to be some radius to the bend.

        I agree with Forrest - don't look to big-box home improvement stores for metal stock. You're better off finding a local scrap yard, steel yard or even welding/machine shop that sells drops and small quantities to the public. You can also investigate the cost effectiveness of ordering if from places like Speedymetals, Onlinemetals, Mcmaster-Carr, etc. Usually cheaper to buy local once you factor in shipping, but not always.

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        • #5
          Absolutely do not buy metal stock at Home Depot unless you only need a little and they have almost exactly what you want. I've been making things out of steel since the 1960s. If I had to make those exact shapes I'd start with excess length and make the two interior bends on one piece and then the other. Then sit them exactly next to each other and mark both together for leg height. Then cut them off there and recheck. Sand to make the heights match if necessary. It's one thing if a little table has a leg pair bent just slightly differently from the other, but it's much worse if the table isn't level. Once all 4 legs are the same height, turn the legs upside down and set them down on four tabs (or two whole pieces of flat, that's more likely how I'd make it) then weld it up carefully and sand smooth. I'd start with cold rolled flat bar. It costs a little more but it looks much nicer without the scale.

          The best way to form those interior bends is with a press brake. If you don't have one, clamp the bar to your steel table so it's square to an edge and the bend mark is lined up with the edge. Then heat the bar to bright red with an oxy/fuel torch and make your bend. Make a template first so you can measure it in place while it's still hot.

          I think if you used flat stock at least 3/16" thick and bolted those legs solidly to a sturdy table top, that the metal would be stiff enough. Forrest is correct, of course - metal is like rubber only stiffer, and flat bar flexes more easily in the flat direction. But for an end table holding up a lamp or something I think it would be fine. If you were going to use it to hold up one end of a truck, forget it.

          metalmagpie

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          • #6
            Tops are welded... you can see the remains of the bead, and anyhow you cannot get the sharp bends with a point on the bend exterior.

            But that's not relevant, really. A bend can be made there instead of a weld, it just will not be sharp pointed like that. Might actually look better for that style.

            As for HD, they don;t get the best, but their stuff is usually usable. If you want certs, you ain't gettin them, HD would not know an alloy number if it flew up their nose, they don't know what they bought, and neither will you. But for generic steel or aluminum, hey have it , it's just too expensive.
            Last edited by J Tiers; 07-28-2016, 12:11 PM.
            CNC machines only go through the motions.

            Ideas expressed may be mine, or from anyone else in the universe.
            Not responsible for clerical errors. Or those made by lay people either.
            Number formats and units may be chosen at random depending on what day it is.
            I reserve the right to use a number system with any integer base without prior notice.
            Generalizations are understood to be "often" true, but not true in every case.

            Comment


            • #7
              I'll just echo the idea that 1/8x1 aluminium has no place in any such furniture application. It's not so weak that it'll collapse the first time you put a full cup of coffee on the table but it won't be far off that.

              You've pretty clearly not used that size of aluminium very much or you'd already know this.

              For a coffee table or end table I would not go with less than 1/4 x 1 STEEL bar. And the reason why is because it will resist bending and collapsing to a far higher degree if someone sits on the table or you load it down with a few boxes of something in the future.

              The downside is that 1/4x1 doesn't bend cleanly if you're not using a proper bender such as the metal bender sold by Harbor Freight or something similar. Hammering it in a vise to the right angle CAN be done but it's not a pretty thing and unless your vise is attached to a pretty sturdy bench that is securely fastened down with lots of heavy stuff or with bolts you'll likely find the vise moving around with you and the flat bar.

              Finally, I could be wrong because there's no scale in the picture to go by but that metal looks a lot more like it is something like 3/16 or 1/4 thick by closer to 3 inches wide. And in my experience that sort of size is FAR more what I'd want to see on any sort of coffee table where someone might someday sit on it or I might set down a heavy box of books on occasion. And there's simply no way you are going to bend anything like that in your vise with a hammer. It would even be more than is possible in one of the HF or similar bar benders.

              So really, in short anything you can easily bend in your vise is not going to be suitable for legs on any sort of table you can think about. If you can easily bend it in the vise it'll easily collapse at the first sign of any normal load such as someone simply leaning on it. If it's something you have to work really hard at to bend in your vise and hammer a lot to bend it then it'll be closer but still not something you'd want to stand on or sit on if the need should arise some day.

              If you really want to pursue this idea you'd be better off buying the flat bar that is a suitable size from a proper metal supplier and cutting and welding ALL the corners. That way you can deal with the size of metal needed for a sturdy enough leg. Or find a local metal fabrication shop and just pay them to make the bends in these legs for you on their machinery. If you have a welder you could save some money by welding the top mounts and any mounts for a shelf yourself.
              Last edited by BCRider; 07-28-2016, 01:55 PM.
              Chilliwack BC, Canada

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              • #8
                my 300T brake would make short work of that!

                100% agree on steel, and agree 1/4 seems right. If you don't have a brake press or hydraulic press and dies, that's about a 99.9999% probability for someone new to metalworking, you do a very neat job of the bends with a torch. You'd need access to a bench vise and O/A or O/P torch. One minute with the torch (get a line across it red hot) and it requires almost no force to bend. make templates (cardboard) to get the angles the same. The bend radius could be a little more than with a brake, but that's how with minimal equipment to do a neat, workman like job of it.

                end of the day, unless you want to pursue metal working, its likely not worth even acquiring a torch.....so agree with BC..... take the thing to local weld shop with the least knuckle to floor contact
                Last edited by Mcgyver; 07-28-2016, 04:35 PM.
                in Toronto Ontario - where are you?

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                • #9
                  I made a steel (!!) camera frame out of angle from the local home store.
                  The miters were done on the SB9 milling attchment, then silver soldered together and faced in the 4 jaw.
                  It is one way to get a fairly accurate steel frame.
                  https://app.box.com/s/xemi6n4vwa1a1h234l4gy4zg9w0yggo0
                  The edges were linished in the bench vice using a belt sander.
                  But that steel did not end up with a smooth face ( gummy) and was speckled with hard inclusions.
                  Next time I will order some better quality angle on-line.
                  Last edited by wombat2go; 07-28-2016, 04:15 PM.

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                  • #10
                    I have to almost completely agree with BCRider. You say it will take an 8' length to make one of these so I am assuming the sections are around 3', 2', and 3' with the 3' ones being the uprights. There is no way that I would trust that to 1/8" aluminum unless the width of those aluminum "strips" is measured in feet, not inches. 1/8" aluminum would be asking, begging for disaster.

                    Steel will probably work, but I would choose the alloy carefully.

                    In any case, I would try to add some decorative braces in the four corners. They would make it a LOT stronger. The bigger they are, the better. Or a cross piece about half way up. Or diagonals from the mid points of the uprights to the center of the between their tops. Something to make it more "structural".
                    Paul A.
                    SE Texas

                    And if you look REAL close at an analog signal,
                    You will find that it has discrete steps.

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                    • #11
                      Sharp bends in steel flat bar? It can be done accurately with a little care and some simple two pin jigging. The inside radius will not be perfectly sharp. You can reasonably expect 2 1/2 r on a good cold bend and 1 1/2 r on a hot bend. An inside radius about 1/2 the material thickness would be the practical limit for a hot bend followed by a careful fettling session. You really don't want a bend with an actual shape inside corner anyway because if stressed they are subject to crack propagation and fatigue.

                      I've bent miles of flat bar one time or another. I often made simple bending jigs of wood with metal hard points where a bend needed to be. If the bend had to be sharp I heated the zone and then narrowed it to a red strip across the bar (a step called "heat trapping" IIRC) by local quenching, then, quick as a bunny bent the bar at the heated zone in the jig. A wood maul or a flatter (a blacksmith tool resembling a hammer with a wide flat face) struck with a hammer can tighten the bends to almost sharp inside corners within the limits mentioned above.

                      Steel working is a skill. You may need to make a few practice bends to evolve a predictable process.

                      I often had to bend larger flat bar and for that I sacrificed an OA welding tip and silver brazed a row of wire feed contact bushings in a row along one side to form a strip heater that was frightening to light. It really gobbled acetylene at 14 PSI but it would heat a uniform red strip across a 1/2 x 4 flat in about a minute. I like to cool the outside of the bend to a dark red to encourage upsetting on the inside a trick which made the bend zone a trifle thicker.

                      If you want to get into metalworking I suggest Tom Lipton's book "Metalworking: Doing it Better" as a tutorial and general reference for the aspiring metalworker.

                      Like everything out of your experience, in metalworking you have to think a little, practice a little, and maybe make find resources to help you do it.
                      Last edited by Forrest Addy; 07-28-2016, 07:00 PM.

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