Possible newb question but I searched....

[docjake]

I know that when you are making a bend in tube it increases the size of what you are working on, I am not sure the numbers but I know it does. For example if you start a bend at "A" the length increases to "B" if that makes any sense. I am planning on bending a piece of flat 3/16th at a 90 degree angle what can I expect to add to my corner. For example if I bend it at 12 inches will it end up at 12.25 inches at the outside diameter?

 

[4X4HIGH]

If you used 3/16" flatbar and made a mark 12" from the end and made your bend on the line then it would be 12" in length to the inside of the bend and 12 3/16" to the outside of the bend. So now you just need to know if you want the inside or outside dimension as your final dimension. If you want 12" to the outside then you would make your mark at 11 13/16" to achieve a 12" to the outside of the bend.

 

[rdn2blazer]

Best thing to do if your not sure is to do some sample bends on a extra piece of steel. Make some marks for refference on it too, that will help alot in figuring out what you need to add or subtract.

 

[tRustyK5]

If you used 3/16" flatbar and made a mark 12" from the end and made your bend on the line then it would be 12" in length to the inside of the bend and 12 3/16" to the outside of the bend. So now you just need to know if you want the inside or outside dimension as your final dimension. If you want 12" to the outside then you would make your mark at 11 13/16" to achieve a 12" to the outside of the bend.

Generally yes. You're going to gain that 3/16" in both directions though. Example, 24" long piece of flat bar bent at the exact center. Inside dimension of each leg will be 12". Outside overall dimension of both legs will be 12 3/16". Total theoretical gain of 3/8".

It does depend on the die radius though. For a sharp bend (die rad equal or less than the material thickness) that info should be close enough. As Rob mentioned, a sample bend is the best way to get an accurate idea of what you're going to gain from material stretch in the bend area.

It's easier to work off of inside dimensions in general, at least for simple bends. It's when you get multiple bends on both sides of the material that things get trickier.

I spent a few years running the press brake, although never in a full production capacity. Mostly between one and 10 parts at a time. Sheet metal brackets to 1" thick x 6" wide using a 2.5" rad upper die. Most of the drawings I got came with a theoretical overall length of the part, plus a flat pattern that gave me the bend centers and angle of each bend. I quickly learned that you couldn't take any of that to the bank if you wanted a good part. I always bent up sample pieces after that.

Rene

 

[docjake]

If you are bending a piece say in half and then on the ends (like a box) does that require a special bender?

 

[Blaze]

Finger break.

 

[tRustyK5]

With flat bar it's pretty easy. Bend the two outer bends first, then the middle bend last which will close the box on the bender. Gently pry it open enough to extricate it and you're good to go. The flat bar should be flexible enough...

Rene