Brake press fab for shop press

I am working on a simplified version of Northern Tools brake press: http://www2.northerntool.com/metal-fabrication/shop-presses/item-145531.htm
With the lower die at 90 degrees (I am using a piece of scrap angle, 3x3x0.5 wall), I presume the upper die should be less than 90 deg. Correct? I am thinking of about 80 degree angle. Your thoughts?
My brake press will have a 11.25 length working surface (mainly because the piece of 1x4 CRS scrap that I have is 11.25 long) and at this time I am going to try to make it work without the two guide posts.
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On Jan 20, 11:51am, snipped-for-privacy@c3net.net wrote:

On my Central Machinery 3-in-1 sheet metal machine the upper die angle measures 80. The lower die, which I can't easily measure, is slightly more than 90.
jw
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I don't know about the exact angles, but I think a couple of degrees would be enough. But, I don't think you will be happy with the lower die being so big (3 X 3). You only need a half inch or so of "vee". If you have much more, you will have trouble keeping things centered as the upper die descends and you will be bending the work all the way from the edges 1 1/2" away from the center. So, I think you'd see a curving bend either side of the desired bend.
I am no expert at this, but check out my solution at:
http://www.spaco.org/Press.htm
You can see one of my brakes on the floor in a couple of pix. I used 90 degrees on both dies because 1.) the upper die is just a piece of 1 1/2" Sq and the bottom die was milled with an endmill.
By the way, my brakes are all mild steel. That works okay, but if I am bending narrow thick things, I can dent and scratch the lower die. If I did it again, I'd sure use tool steel, probably 4140.
Actually, for the first brake I made, I used a piece of 1" square mild steel for the upper die and I just welded 2 quarter inch thick plates side by side to a bigger plate, leaving a 1/2" gap between them. It worked quite well. Shallower is better!!!
Pete Stanaitis ------------------------------
snipped-for-privacy@c3net.net wrote:

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On 20 Jan, 16:51, snipped-for-privacy@c3net.net wrote:

In the States you seem to prefer a 90 deg bottom die.This means you need to coin the material.Elsewhere in the world we work with 87 degrees.This allows for air bending which takes infinitely less tonnage. Something to bear in mind is that on average mild steel will spring back 3 degs,so bottoming the material in an 87 deg die will result in a average 90 deg bend.
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Thanks for the replys. I picked the heavy angle since I wanted the bottom die to be strong and was not planning on milling it from a big chunk of steel. At my local structural metal dealer, they did not have much selection in drops that were a (relatively) heavy gage. I was looking for something more like a 2x2 angle. I figured that I would simply make do with what ever the resultant angle was.
Pete: thanks for the link to your press and dies. It has been years since I bent anything on a press, back then the dies were pre-existing and I never gave a thought to the fact that I needed to have very short legs on the bottom die. I need to study your web page a bit more thouroughly and them I suspect that I will have some questions. My press is a 30T bottle jack setup. I snagged a new hydraulic pump/ reserviour set at an auction several years ago and someday I hope to replumb the bottle jack - sacrificing max pressure for the benifit of being able to better hold my work when pressing.
So now I am interested in cutting down the legs of the angle. Years ago I procurrred some side mill cutters and arbors at an auction (and never found a need to use them). They look something like this: http://www.wttool.com/product-exec/product_id/28632/nm/Plain_Tooth_Side_Milling_Cutters_WT_Import_
Now I figure that I could put one of them to use by cutting down the legs of the angle and learn a bit on how to use them. Any special things I need to know that are unique to side milling? I figure that I will need to use lubricant and keep the cutter speed (tips) fairly slow.
On Jan 20, 4:33pm, snipped-for-privacy@ems-fife.co.uk wrote:

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