press brake info wanted

[davedj1]

I have one that I made a year or so ago and it works fine for thinner stuff up to 20" wide or so. Problem is I want on that will bend 1/4" by 6" stock.
The problem I'm having is how far to space the lower die or what size angle iron I should use. Any suggestions.

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^ ^
given that the two lower angles are touching each other in the center or close to it anyway. My top die is 3/8" x 6". I'm thinking I will either go with 2" angle on the bottoms or maybe one 3" angle for the bottom facing up?

thanks,
dave

 

[npalen]

The rule of thumb for air bending is the distance between the two sides of the bottom V die should be eight times the thickness of material. In other words, for bending 1/4" thickness steel, the optimum width of the lower die would be 2". (1/4" thickness X 8) This will normally produce an inside bend radius on the part that is approximately the same as the material thickness. Using a top die (or punch as it is sometimes referred to) with the same radius as the material thickness is probably ideal for getting a smooth inside radius. Using a sharper radius top die won't change the radius significantly but will tend to leave an indentation which is sometimes mistakenly called the bend radius. Air bending, for those who might not be familiar with the term, simply refers to the fact that the upper die and material being bent are not bottomed out into the lower die. The factor of eight mentioned above controls the inside bend radius.
Using angle iron works great for the most part but doesn't allow for springback when making a bend consequently the actual formed angle will be a couple degrees less than 90 degrees. Commercial bending dies are normally made with an included V angle of a couple degrees under 90 to allow for springback.
Here is some useful info on bending tonnage requirements for various material thicknesses and bottom die widths. Note that the tonnage goes up dramatically when using a narrower bottom die.
PRESS BRAKE TOOLING

 

[davedj1]

Thanks for taking the time to enlighten me. I am thinking about how to get under 90 deg.

 

[npalen]

I've seen lower dies made using, for example, two pieces of 1/2" steel rod welded to riser blocks and spaced apart appropriately. The radius on the rods serve to minimize gouging of the part being formed.
The rods have to be high enough above the base plate to allow the maximum bend angle needed allowing for springback.

 

[600rider]

do you really think you are going to bend 1/4" material by hand???? You had better have a huge counter weight or gorilla arms....or both!!!! LOL
the bigger the radius on the punch and the bigger the bottom die opening the easier it will bend. Also with the bigger radius the more material you will use.

 

[dstig1]

Very useful link...

600rider - I am assuming this is in a hydraulic press, and not being done by hand...

 

[davedj1]

do you really think you are going to bend 1/4" material by hand???? You had better have a huge counter weight or gorilla arms....or both!!!! LOL
the bigger the radius on the punch and the bigger the bottom die opening the easier it will bend. Also with the bigger radius the more material you will use.

Ummm, yes! I just assumed that everyone knew the press brake goes in a hydraulic press, my bad. I have it set up now and I can bend 1/8" up to 20" wide, 1/4" x 2-3" is no problem but when I get to 4" it won't quite do it. That is the reason I am making a new die.

 

[davedj1]

I found a piece of 2 x 2 x 1/4 angle in the shop, cut some 1 1/4 strips for supports and welded it all to a piece of 3/8 x 6 plate, works like a charm. I bent some 1/4 x 4 so easy it wasn't even funny.
lVl kind of like this
thanks again,
dave

 

[Stimw]

I have a 50 ton (rated at the punch) Scotchman Ironworker.
I made a press brake for it. For the bottom I used 3 pieces of 1/4" X 2 X 2 angle iron in an upside down "W" . Top die is a piece of 3/4" steel gound to a "V" and then radiused.
I can bend 1/4" x 12" (brake width) or 1/2" X 4" with no problems.

 

[davedj1]

Stimw, that is cool! I would be in heaven if I could ever get an Ironworker. There is a shop that I get some metal from and they have like three or four of them, I would like to be trapped in that building for a weekend! LOL
Looks like your brake has had some use too.
I'm only running a 12.5 ton air over hydraulic jack at the moment, the whole press is homemade. I may try a piece of 3/8 x 6 that I have just for fun. I have a 20 ton jack that i would have to run manually if needed. The die is sitting on a piece of 5" I beam so I don't think that will move.