Sheet metal: How do you bend a flange that interferes with the one next to it?

Phase · Jan 1, 2023

Hi folks,

What is the best way to bend the middle flange?

Once that middle one is done, I can do the rest on a 4-foot hand brake. But without bending that first, the bending leaf in the brake also bends part of the next flange. The main issue is in the left where the angle is very wide.

I have 4 of these to do. Two in 0.040" and two in 0.125" aluminum. The flange is 14" x 1". The rest of the part is roughly 4 feet x 3 feet. The bend is on this part for aesthetics, plus there is not enough room in standard 4'x10' sheets to make the flange on the other part this one attaches to. Thanks!

paulz · Jan 1, 2023

Box and pan brake.

Phil in Montana · Jan 1, 2023

New to the trade?...Phil

Phase · Jan 1, 2023

Yes, very new... LOL

Sorry, I can see how to do it if the angles were 90, but I can't figure out how set up the box and pan brake to make that bend without bending the other flanges next to it.

Only the fingers are removable and adjustable. So if the next flange is already bent you can just remove those, but you have to bend one of the two first. Otherwise, the bending leaf, which is one 48" piece, comes up and bends anything that is on that line.

Am I missing something? I hope I am... LOL

specfab · Jan 1, 2023

Press brake with bottom and top dies at just the right length. There is indeed an issue with trying to do that on a manual box/pan brake. "Good design" in sheet metal generally should stay away from that sort of configuration, but sometimes it's required.

Phase · Jan 1, 2023

Bummer.

50BMG DUDE · Jan 1, 2023

You need to find somebody with a small pressbrake to bend that. Bottom and top dies are removable/swapable to do what you need

deltap · Jan 1, 2023

Bend the middle one first. Do not use the leaf. Mount it upside down with the bend line on the front edge of the leaf. Use a rubber or wood mallet to gradually make the bend downward. The aluminium will require a bend radius to prevent cracking.

Pattnmaker · Jan 1, 2023

Haven't used a box and pan brake since grade 8 but could you not bend all the flage bends. Then drop a piece of flat bar on the bending leaf before closing fingers . Just closing fingers might be enough to bend that bend. If not bend leaf with flat bar there.

Phase · Jan 2, 2023

deltap said:
Bend the middle one first. Do not use the leaf. Mount it upside down with the bend line on the front edge of the leaf. Use a rubber or wood mallet to gradually make the bend downward. The aluminium will require a bend radius to prevent cracking.

I think this is gonna work. The table from the shears might have just the right radius to be close enough that if I go easy with a mallet it kind of matches the bend of the brake. Plus it supports the sheet and has means to bolt it down by the edge. Thanks!

metalmagpie · Jan 4, 2023

Magnetic box & pan brake

Bondo · Jan 4, 2023

You should be able to bend the left side, then move the panel to the left side so the 1st bend is next to the fingers. Make the middle bend and you will probably buckle the corner of that flange just a little going up. Stop at the top and release because if you go down, that is when you really damage the 3rd flange. Then move to the left and bend that one as well.

By releasing at the top, the 3rd flange should have bowed a little under stress, but when you go down, that corner grabs stuff on the way back and then it's screwed up.

Also depends on how your box and pan brake is setup. Some are a lot easier to do odd things on then some others.

BT Fabrication · Jan 5, 2023

press brake with smaller removeable sections, happens all the time when bending, but a pain as you need to set each die to each length bent.

gbent · Jan 5, 2023

Leave the fingers out for the left flange, and bend the center. The left flange will bend, just with a large radius and less than 90 angle. Straighten the bent corner of the left flange and make your bend. Mating corners are a pita using a standard apron brake. This piece was not designed with an apron brake in mind.

Fish On · Jan 5, 2023

The 'right' way to do it on a hand brake is to use one that has sectional fingers on both the leaf and the apron. These are a bit of a rarity, but they do exist. This one even had removable sections on the bed.

2800-48-16-R, Mittler Bros Ultimate Box and Pan Brake, Radius Fingers

Mittler Bros Ultimate Box and Pan Brake features removeable upper and lower fingers. This brake is equipped with radius fingers, ideal for aluminum work.

www.trick-tools.com

On a more conventional box and pan brake, with fingers on the apron only, set up just enough fingers for the bend you're doing, and sneak up on the bends 20 degrees at a time. Do an outer bend first, just 20 degrees worth, unclamp and do the other outer one at 20 degrees. Then, bend the middle one 40 degrees, then go back and hit each outer one, then back to the middle, etc.

By only going 20 degrees at a time, you should stay within the elastic limits of the flanges that have no fingers over them.

Strostkovy · Jan 10, 2023

Only the die needs to be the correct length.
If you have a press brake but your tooling is too long, do the rightmost bend first. Then do the middle bend with the punch overhanging left and the die overhanging right. Then do the left bend.

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Sheet metal: How do you bend a flange that interferes with the one next to it?

Phase

Aluminum

paulz

Aluminum

Phil in Montana

Stainless

Phase

Aluminum

specfab

Titanium

Phase

Aluminum

50BMG DUDE

Aluminum

deltap

Cast Iron

Pattnmaker

Stainless

Phase

Aluminum

metalmagpie

Titanium

Bondo

Hot Rolled

BT Fabrication

Stainless

gbent

Diamond

Fish On

Hot Rolled

2800-48-16-R, Mittler Bros Ultimate Box and Pan Brake, Radius Fingers

Strostkovy

Stainless

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