Square Tubing - Tight Radius Bends?

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Drawing specs out 3/4" square steel tubing bent 90* with a radius of <1". Wall thickness is "my best recommendation". My plan was to tack caps on one end, fill with sand, then tack cap on other end. Then weld a 3/4" bar to the top of an old vice jaw, clamp the material in a vice, heat till it's glowing, and bend over the bar. Is there a better way to do this or do any of you see a problem with this?John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:I'm not a professional fabricator but in my experiences trying to bend a tight radius in sq tubing I got a lot of deformation.   The sides will crimp and sometimes tear.  I trying both hot and cold working it.  Being only 3/4" you might consider solid bar as it will bend nice and clean.Sent from my SCH-I545 using Tapatalk
Reply:It will crater on the inside and outside of the bend and bulge on the top and bottom.  How much depends on wall thickness.  Like suggested, you could try solid bar but I doubt much better results on that tight of a radius because of the amount of heat it will take.Larger radius would be better... or miter cut and weld.  From the instructions (especially the wall thickness part) it seems that the drawing was done by someone who isn't familiar with metal fabrication.GravelThe difference between theory and practice is that in theory there is no difference.
Reply:Square tubing is a pain to bend.  First off, I doubt if you will ever obtain anything close to a 1" radius bend in 3/4" tubing without smashing it in the process.Whenever tubing is bent a few things are happening all at the same time.  a. the outer surface is stretching.b. the inner surface needs to shrink or deform in such a way as to tuck the extra material from the decreased length of the material.c. the side walls are both stretching and shrinking at the same time.  To accomplish the inner radius shrinkage most square tubing dies use a rounded face to deform the inside edge in a controlled manner allowing the ruffles to form in a somewhat controlled manner.  The sides of the dies support the sides of the tubing to prevent the outer surface from smashing the walls outward while the outer surface stretches about the radius of the bend.Like I said, a lot happening and the materiel is dictating the process and limits.Can you get an acceptable corner by mitering the joint and welding?RogerOld, Tired, and GRUMPYSalesman will call, Batteries not included, Assembly is required, and FREE ADVICE IS WORTH EXACTLY WHAT YOU PAY FOR IT!Dial Arc 250HFThunderbolt 225 AC/DCAssorted A/O torches
Reply:Unfortunately 3/4" solid will be too heavy and expensive. I'd really like to have an edge over my competition as this is still being quoted, and I can guarantee all the other shops will tell the customer exactly what you guys are saying. So even with lots of heat and sand, this will warp, and possibly tear, to a point that can't be ground and hammered back into shape? It needs to look decorative in the end as it's part of a furniture build.John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:You could make just the radius from solid, then weld tubing to it and grind and blend so it appears seamless.  What exactly are you making? Sent from my SCH-I545 using Tapatalk
Reply:Originally Posted by EcondronUnfortunately 3/4" solid will be too heavy and expensive. I'd really like to have an edge over my competition as this is still being quoted, and I can guarantee all the other shops will tell the customer exactly what you guys are saying. So even with lots of heat and sand, this will warp, and possibly tear, to a point that can't be ground and hammered back into shape? It needs to look decorative in the end as it's part of a furniture build.
Reply:Originally Posted by EcondronUnfortunately 3/4" solid will be too heavy and expensive. I'd really like to have an edge over my competition as this is still being quoted, and I can guarantee all the other shops will tell the customer exactly what you guys are saying. So even with lots of heat and sand, this will warp, and possibly tear, to a point that can't be ground and hammered back into shape? It needs to look decorative in the end as it's part of a furniture build.
Reply:Originally Posted by EcondronUnfortunately 3/4" solid will be too heavy and expensive. I'd really like to have an edge over my competition as this is still being quoted, and I can guarantee all the other shops will tell the customer exactly what you guys are saying. So even with lots of heat and sand, this will warp, and possibly tear, to a point that can't be ground and hammered back into shape? It needs to look decorative in the end as it's part of a furniture build.
Reply:Ok, sand is not some magical maintain-the-shape-of-the-tubing material. The whole "fill with sand and bend" thing only works with ROUND tubing (and pipe), and will not really help on square or any other shape.The reason for this is a very simple rule of geometry that says: the circle is the shape of maximum area for a given perimeter. For example, if you only had a fixed length of fencing, setting it up in a circle would give you the maximum possible enclosed area.When you fill a round tube with sand, you are filling it with, essentially, an incompressible fluid. This means that, when bending, for the cross section at any given point cannot change unless there is a reduction in area (compression of the sand) or an increase in perimeter (the steel has to stretch). Since sand is very hard to compress and steel has a high tensile strength, the tube mostly maintains roundness.However, with square tubing, many of the ways it could deform would result in an increase in cross sectional area, meaning the sand is not being compressed and is therefore not doing any good.Visit Tensaiteki.com
Reply:I did table legs like this.  3"x1" tubing that I rolled into 2- 29" half circles.  Was about 140 cuts that had to get welded but turned out cool I think  Attached Images
Reply:Originally Posted by GravelYou may try this:  Miter the corner but don't cut the outside surface of the bend.  Bend the tubing together and weld the 3 sides that were cut.Someone else can describe this better or draw a picture because I know I'm not describing it well...
Reply:Strange, it rearranged my pictures....  they were in order.  You get the point.  Like gravel suggested that would be best bet to bend tubing with least amount of deformity.  You would have to make pie slices with that tight of radius and then bend, weld then grind and sand smooth.   Sent from my SCH-I545 using Tapatalk
Reply:Originally Posted by GravelYou may try this:  Miter the corner but don't cut the outside surface of the bend.  Bend the tubing together and weld the 3 sides that were cut.Someone else can describe this better or draw a picture because I know I'm not describing it well...
Reply:Originally Posted by Going nowhereI did table legs like this.  3"x1" tubing that I rolled into 2- 29" half circles.  Was about 140 cuts that had to get welded but turned out cool I think
Reply:Originally Posted by GravelI agree. Turned out nice! If you had to do it again would you do the relief cuts or would you use a tubing roller?
Reply:Originally Posted by asdfDo you mean this: not too clever in MS Paint, but notch a V into 2 sides of the tube, bend at the apex of the V, and weld the collapsed legs together?
Reply:Originally Posted by Going nowherethat's what I was thinking and I believe that's what gravel was saying.
Reply:I'm currently working on 20 chair frames so looking for anything to break up the monotony.  Almost welded a wasp that landed on my table....Sent from my SCH-I545 using Tapatalk
Reply:Just spec out 3/4x3/4x3/8 wall tubing, and bend hot or cold, very little deformation. I have bent thousands of 3/4" bars, as well as twisted it hot or cold. So, whatcha building?
Reply:Originally Posted by walkerJust spec out 3/4x3/4x3/8 wall tubing, and bend hot or cold, very little deformation. I have bent thousands of 3/4" bars, as well as twisted it hot or cold. So, whatcha building?
Reply:There is one other way.  Not sure if you can get down to 1" radius.If you take square tubing and slice it down the middle so you have two channels, you can then bend one channel, followed by the other channel and then weld back together.  Very little deformation but you really need to slice it carefully (right down the middle!).One channel will from the inside radius, the other will form the outside radius.  You don't slice it all the way, you need something to hold on to.You might have to tack weld the outter piece as you bend.   This technique is in Ron Covell's working with tubing video/dvdI know if you are doing larger radius bends it makes the square tubing look like zero deformation.A different way:Now if you are saying that you need the inside radius to be 1" (or even the outside), I'd suggest you make cuts from the outside, bend it, and then cap it (filling in the now expanded cuts).Con Fuse!Miller Dynasty 350Millermatic 350P-Spoolmatic 30AMiller Multimatic 200Hypertherm PowerMax 1000G3Miller Maxstar 200DX
Reply:They're just simple table legs. Considering he wanted them done cheap, I told him I'd miter, weld, and blend for $25/each and he took it. I figured offering suggestions and being honest is better customer service than simply quoting too high just to get what they want. Though I would have been happy to charge $100/each to cut a bunch of notches, bend, and, weld, and blend, I doubt he would have taken it. Thanks for all the suggestions though, I'll add those to my mental book of tips! I really like the look of those bends and welds, Going Nowhere. How did you bend the pieces once you cut them? In a tubing roller? I have a tubing roller so maybe I'll give it a shot and make a sample piece to show to prospective customers.John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:Thanks.  I just have a harbor freight tubing roller, bought the 1/2" sq tube dies from hf and the  weld on extensions from swag offroad.  Swag also sells a bunch of dies and upgraded shaft that I've thought about getting. Sometimes multiple options are good if you don't know clients budget.  Sent from my SCH-I545 using Tapatalk
Reply:http://weldingweb.com/vbb/showthread.php...igh&highlight= Heres what I did, it gave me a 12'' raidius though.Nothing Ever Got Done By Quitting, Never Give Up.Hello Econdron, I realize that you have already pulled the trigger to address your questions, yet I might include a couple of photos of some aluminum 1" square tube that my partner and I bent for his golf cart top. This was done on a Hossfeld bender with some homemade dies. The centerline radius of this bending set-up is roughly 3" and it's a little hard to see but the wrap-around die has a raised center rib to intentionally collapse the internal portion of the bend and assist with minimizing wrinkling. The outer "shoe" fits fairly tightly to the outside half of the tube and is "rolled" around the outer radius of the die with some ball bearings on the pin in the Hossfeld's arm. Best regards, Allan Attached Imagesaevald
Reply:Here's an additional sketch to explain the "die action" a bit further. Best regards, Allan Attached Imagesaevald
Reply:one technique that is not used much anymore is to fill the square tube with a low temp melting alloy like Bismuth.  This creates a solid bar.  when you are done playing you remove the alloy with a heat gun or boiling water.  You can get it to melt as low as 150 degrees.
Reply:Originally Posted by walkerJust spec out 3/4x3/4x3/8 wall tubing, and bend hot or cold, very little deformation. I have bent thousands of 3/4" bars, as well as twisted it hot or cold. So, whatcha building?
Reply:Originally Posted by ironwrx3/4x3/4x3/8 wall tubing?????? Seriously????? (That would be 3/4 square SOLID wouldn't it?)Sent from my iPhone using Tapatalk
Reply:Yep, much easier to bend solid bar.
Reply:I agree. Sorry for my blonde moment,  I see now my response should have been Lol!Sent from my iPhone using Tapatalk