Brakes - box, pan...

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Can someone please give me a breakdown on brakes. I currently need to make some simple "U" brackets with the sides being 1.5" apart. The stock is 1/8" aluminum, 4" wide. All of the specs I see are for lighter stock, but wider widths. No where have I found the maximum setting for smaller widths and how do I know I will have room for my second bend?No doubt I will need this brake in the future, so I want to buy bigger than needed now.Thanks!Millermatic 350PPython p/p gunLincoln 135"Welding aluminum is'nt difficult, just DIFFERENT"Madison, WI area
Reply:Sheet metal brakes are generally made for up to 16 ga metal.Half the thickness of your aluminum. Much bending of 1/8", even aluminum, will spring a 16ga brake, ruining it.A 4foot 16 ga brake will NOT bend 2 feet of 1/8". They arent built heavy enough, especially cheap chinese ones.1/8" thick brakes are big, heavy, and expensive. I have a 4 foot Chicago D&K, a good made in america brand of box and pan that is rated for 12 ga- which means it will do 1/8" aluminum, but not 1/8" steel. It weighs in at around a ton, and cost over 6 grand new. Used, a good price is $2500 to $3000.Or you can use a press brake- old mechanical ones are sometimes available cheap, depending on where you live. New, hydraulic ones can easily run 5 grand or more for 4 foot width, usually a lot more.U brackets are better bent in a smaller bender, not a brake. I use my Hossfeld bender for brackets like you are talking about. Max width is 4", but it will bend up to 1/2" x 4" cold quite easily, thicker stuff hot. I have bent 1" x 4" hot into a driveline loop for my little tractor with it.There are formulas for finding bend allowances, but they vary a bit from material to material, and I always do better with just doing a test bend and measuring it.
Reply:Here is a bend length equation I use that works pretty well.Bend Length = (angle/90) * (material constant * thickness + (pi*radius/2))Material ContantsAluminum = 0.683Steel = 0.71This calculates the length of your bend. The "radius" is the inner bend radius.  I believe (don't quote me) this is the equation most CAD programs use to create the flattened view.