bending flatbar

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hi everyone,i hope no one minds, but i thought i would post my question here, since this is one of the more popular forums and gets lots of readers.i occasionally have to bend flatbar at my shop to make brackets for misc. projects.  most of the time my bends are more trial and error than actually getting the measurements i was after.  i'm looking for a simple formula or rule-of-thumb for laying out lines on my piece prior to bending so that i don't have to scrap or cut and re-weld to hit my mark.  someone told me to add half the material thickness or subtract half the thickness when bending material. if this is so, what is the appropriate action to take? do you add material bending one direction and minus bending the other?i included a basic sketch of a typical bracket i would have to bend in our  modest brake.  with the measurements i provided, i was hoping someone could help me with the math laying out this project staring from left to right, assuming i was starting with a 3/8" x 2" flatbar.any suggestions would be greatly appreciated.bill Attached Images
Reply:So the material is .375 Thick and two inches wide?  What bend radius?  Lets say you have a 3/8 inside bend radius.  I am also assuming the dimensions are  to the outside.  First we find the bend deduction.Two material thicknesses equals .75 and two radii are .75 added together, 1.5 inches. Now Material thickness .375 x .44, plus radius .375 equals .54 .54 x 3.14159 equals 1.696.  This is the amount of material in 180 degrees of bend.  Divide by two and this is the amount of material in a 90 degree bend.  And that will be .848  1.5 minus .848 equals .652 and this is the number we a looking for.  .652 is the bend deduction for 3/8 thick and 3/8 radius.2 + 10 + 14 + 10 + 3 = 39 minus four bend deductions (4x.652=2.608)equals 36.392 flat pattern length.  Now make your lines,2-.652+10-.652+14-.652+10-.652    The bends will take place between the lines spaced .652 apart.Just remember that this only works when the dimensions are outside to outside.
Reply:Wow... just curious what the .44 is for???
Reply:When you bend metal, it compresses on the inside and stretches on the outside.Inside radius plus 44% material is where the material neither compresses nor stretches.  You could call it the neutral line or where you calculate the amount of material in the bend.  This is one method used in precision sheet metal.
Reply:Originally Posted by Mustangous  Wow... just curious what the .44 is for???
Reply:Or, you could just make it long and cut it to length.   No really, that's a great formula to use when it really counts.  I'll print it and keep it in my binder wiith other important facts.Hobart 140 Handler w/ gasHyperTherm Powermax 380 Plasmaoxy/acetylene
Reply:awesome, thank you so much riley.  man, you know what you're talkin' about.i'm going to try that out out first thing tomorrow.i appreciate your quick response, i'll let everyone know how my progress goes.thanks again,billthebutcher
Reply:Originally Posted by riley mcmillanSo the material is .375 Thick and two inches wide?  What bend radius?  Lets say you have a 3/8 inside bend radius.  I am also assuming the dimensions are  to the outside.  First we find the bend deduction.Two material thicknesses equals .75 and two radii are .75 added together, 1.5 inches. Now Material thickness .375 x .44, plus radius .375 equals .54 .54 x 3.14159 equals 1.696.  This is the amount of material in 180 degrees of bend.  Divide by two and this is the amount of material in a 90 degree bend.  And that will be .848  1.5 minus .848 equals .652 and this is the number we a looking for.  .652 is the bend deduction for 3/8 thick and 3/8 radius.2 + 10 + 14 + 10 + 3 = 39 minus four bend deductions (4x.652=2.608)equals 36.392 flat pattern length.  Now make your lines,2-.652+10-.652+14-.652+10-.652    The bends will take place between the lines spaced .652 apart.Just remember that this only works when the dimensions are outside to outside.
Reply:Originally Posted by MustangousThis is really interesting.... So what determins the inside bend radius? different benders, or brakes? Would would the radius be if someone used a Vise with heat and a hammer? lol.  Thats the way i do small quick stuff because i dont have a break.....Thanks for the info...Great stuff..
Reply:WOW thats a lot of math. i like the idea of cut it long and bend then cut off the excess just cuz i'm to lazy for all the math, realy helpfull though, i think i'll keep a copy also , ya never know when it may be the best way to go. summer is here, plant a tree for mother earth. if you dont have time or space, sponcer some one else to plant one for you.feel free to shoot me a PM or e-mail me at [email][email protected] i got lots of time.
Reply:keepin it long is only good for one bend. What if you have 4 bends like above?
Reply:thats the point to cutting off the extra when you finish with all the bends.the formula is realy good in a production setting but to just make one part it would probly be just as easy and fast to just make the bends and cut off the end. without needing multipls or having a computer to figure out your plans i think maybe just bend and cut for most aplications the dont require verry close tolerances, like .01+/- nost fabricated hangers could be done with the bend and cut, but it dose create more waised matereal. the math is the best way to do it but not the only way. summer is here, plant a tree for mother earth. if you dont have time or space, sponcer some one else to plant one for you.feel free to shoot me a PM or e-mail me at [email][email protected] i got lots of time.
Reply:So your saying you would bent 2 angles with metal left over, then cut/trim to the desired length and then do 2 corner welds?The math really isnt that hard or time consuming. just have to know what it means and I thank riley for that... Again... Great info...
Reply:true its not that hard and i happen to be verry good at math just saying it would depend on the aplication and how precise it needed to be. i supose using a box break would make the hole thing much easyer as aposed to heat and bend methouds. yes he gave us great info, i dont debate that. it all just depends on the bending situation. summer is here, plant a tree for mother earth. if you dont have time or space, sponcer some one else to plant one for you.feel free to shoot me a PM or e-mail me at [email][email protected] i got lots of time.