Thoughts on making a sheet metal brake?

[Flyinfool]

The radii of the bend is determined by the nose radius of the die.
For a press brake to make nice accurate bends you need to use a coining die, air dies are not as accurate.
A box and pan brake will make nice bends as long as it is heavy enough to not flex while making the bend.

 

[Cheeseking]

The radii of the bend is determined by the nose radius of the die.
For a press brake to make nice accurate bends you need to use a coining die, air dies are not as accurate.
A box and pan brake will make nice bends as long as it is heavy enough to not flex while making the bend.

Bend radius is determined by the v-die opening for a given material thickness when air bending.
Specifying IR smaller than .63 x material thickness (on mild steel) is considered “sharp” and poor design practice.

Air bending is extremely accurate provided you have the proper equipment and tooling. We do it all day long.

 

[Chips O'Toole]

I have a SWAG brake on a 20-ton press with air. It's fantastic. It will not put a 90-degree bend in 16" of 1/4" steel, however. I tried to do it, and I got maybe 30 degrees. Maybe heat will help. The site advertises 16" of 1/4" steel. Can't promise that my press isn't the issue. It's from China, after all.

It does bend very heavy metal compared to most factory brakes, however. I have no doubt that I could do 10" of 1/4" plate. I have made big pans from 11-gauge steel with no problems at all. Try that with a 24" Grizzly, which maxes out at 12" of 18-gauge.

Given that factory brakes only bend steel which is about like car bodies, which you could bend just as well with a hammer and blocks of wood, the SWAG brake seems like a phenomenal tool for the price.

 

[Cheeseking]

It will take every bit of 20 tons but using a die with proper v opening you can bend it.
Quick check of a common force chart shows
1/4” mild steel will require 14 tons per foot using a die with 2” V opening. It will require at least 1-3/8” bent flange length and you’ll get approximately a 5/16” inside bend radius.

 

[CNC_noob]

stupoty​

I looked at the 20 ton finger brake, The spec indicates it can bend 5/8 plate, I don't believe it.

The specs indicate it but only a small piece; not the full width of the brake. I’ve not tried it on my brake, but there are videos that show it being done. I have. 20 inch SWAG brake using the HF press kit and it works nicely and have no reason not to think it would bend a small width of 5/8 steel. I just don’t have any need to bend something that big.
This thread is talking about building a 6 Foot brake and so there are some multi bottle jack brakes on the swag site as well as some kits that might help With that design idea.
I for one would love to make a 6 foot finger brake. Unfortunately, I do not have the shop space for it.

 

[CNC_noob]

I am contemplating the idea of making a sheet metal brake. I don't know much about bending sheet metal but I have made some small projects (boat console and some other things) with a cheap brake from Harbor Freight. With the gauge metal I made the console out of, for example, the HF brake was too light duty for bends resembling anything of quality/crispness.

So some design considerations that are in my head at the moment are:
- Ability to put more crisp bends in sheet metal
- Ability to clear 5-6' of width
- Ability to bend complex bends (think 5 sides of a box - bottom and 4 sides as well as 90deg Z bends)

Looking at how the HF brake I have works - the mechanism doesn't seem very difficult to replicate. With heavier metal and some design changes the basic function of it (the clamped piece on the fixed table and hinged press plate) is easy to make. However, I am not sure if there is a logical way on that style press to do complex bends. The kind of brake that mounts to an H frame hydraulic press with the piece being pushed in to a V block, to me, makes more sense for being able to make a complex Z bend, but I don't know how crisp a bend could get. The V block would also mar the outside of the bend (the metal pressed against the V block).

As for generating the pressure I have 2 ideas.
1. Bottle jack. I have a 4-8 ton and the one on my hydraulic press could certainly be used as well - its a 20 ton.
2. Lever. This, preferably, would be powered by a bottle jack, but it would be conceivable to use a long bar or a bar with a cheater pipe, but I think a jack would give me more precision/finesse.

Is my idea crazy and off-the-rocker? Or is there any merit to making my own machine? Does anyone that has good experience with sheet metal work have any words of wisdom on the subject?

I would think using c channel steel cut to order in the style of a press brake would be pretty easy to design and put together within a few days with some welding. The metal likely will be heavy enough where you will need a system to hold them and move them and I would imagine the brake will be too heavy to move once assembled.