Building an Advanced Sheet Metal Tool on the Cheap.
Every trade has it’s own specialized tools. You can do good work with basic tools, but eventually you’ll want to get some of the specialized ones. Metal work has a wonderful variety of tools that are way too expensive for the amateur to justify buying. Building your own turns out to be surprisingly viable.
Bending sheet metal can be done with little more than a hammer and a flat surface or two. I’ve done this for years. Results are… mixed. It’s tough to make good bends by hand. Without a good setup, it’s too easy to put a bend in the wrong place. Sheet metal does not easily un-bend, so at that point you usually have to start over.
Consistently good bends require a bending brake. This is the most basic tool in any sheet metal shop after simple hand tools. You don’t get very far without a decent brake- or a lot of patience.
Making a brake has been on my to-do list for years now. I made a few attempts with little to show. I figure now’s the time to get this one out of the way- I keep coming up with project ideas that need it!
Bending Brake Design
There are two major brake designs: cornice and box-and-pan brakes. They operate identically; the difference is what kinds of work they’re used for.
Cornice brakes are the simplest. They are just a big hinge with a clamp over the top. You can find them dirt cheap at Harbor Freight. Your local “cheap tool” store likely has an identical model; everyone seems to be getting the same tool and slapping their name on it.
Beyond that, there’s no shortage of plans if you’d like to build your own.
Grizzly Industrial T28657 bending brake.
Costs 150USD.
However, if you want to fold a more complex shape you need a box-and-pan brake. As the name implies, these are specially designed to allow for folds perpendicular to each other. Usually these have removable “fingers”, leading to the alternate name finger brake. I’ll use the two terms interchangeably.
Grizzly Industrial G0556 box-and-pan brake.
Costs 295USD plus 159USD freight shipping.
I can handle simple folds with two planks of wood. A light duty cornice brake is dirt cheap, as we’ve already seen. Box-and-pan brakes are stupidly expensive; even the cheap ones are a couple hundred bucks. They’re also solid steel and weigh more than most shipping services will accept. Oh, and I don’t own a car to pick one up in town. Ergo, building a box-and-pan brake is the best option.
Building a Box and Pan Brake
This isn’t my first attempt at building a bending brake. This isn’t my second attempt either- I know I’ve done at least three of them. Maybe four. Five? Do we count the one I stopped building halfway through?
Here’s my last attempt, and the only one where I tried to make a proper finger brake:
“Almost” good enough is still a long way from good enough.
When I tried to use it the brake bent, not the sheet metal. I considered reinforcing it, but it’s just not good enough to put the effort in. Too big, too crooked, too hard to use.
Looking at the sheet metal things I have built, it’s clear I don’t really need this much of a brake. While a long brake would be nice occasionally, I can probably get away with 18″ or less. I only really work with aluminum sheet at most 1mm thick, so I can build it relatively lightly.
Knowing that, I put together some plans based on professional equipment:
A 3D model showing the basic layout. Not quite the final design, but shows the general concept.
Really though, this was not a project that needed detailed plans. Most measurements are not too critical. Trimming the fingers to length is going to require some trial fitting no matter what you do.
Most of my materials came from other, less successful projects. You can get them from any decently stocked hardware store. I chose 1/8″ steel angle for the high-load parts (bending leaf, clamp bar, handles). Everything else is 3/4″ hardwood.
Wood can be used for the high-strength parts, but I found it less practical than just using steel stock. You need much thicker wood than metal.
I have no place to permanently mount the brake (not even semi-permanently) so I had to design it to break down for storage. I provided big smooth areas at the ends to clamp to a workbench. A little lip on the bottom aligns it with the work surface. Glue and screws secure the wood pieces together.
Not much to say about the top. Just a plank with two blocks added for vertical clearance.
On the bottom you see the alignment lip, the screws holding the blocks down, recessed bolt holes, and the sticker I never got around to removing.
The main bending leaf is 24″ long, with 18″ used for bending. This is hinged to the lower jaw with some small hinges. Piano hinges are sometimes used, but I find them too hard to align properly. I guess you could always make your own hinges if you have the equipment.
Basic, but functional. Despite my initial reservations, the bolted joints are holding up well.
Hinges only open about 270 degrees, so make sure they’re pointing the right way. I don’t have welding equipment, so the hinges have to be bolted on. This has the advantage of being easily removed if you do install the hinge the wrong way around. Undoing a weld is rather more difficult.
I took great pains to try and align the hinges with the throat. That would put the rotation axis directly on the workpiece, improving the bend quality. Theoretically, anyways. In practice this seems to be much less critical than I thought it was. You can still get pretty good bends with slapdash tolerances.
Clamping the metal requires a lot of stiffness. Using a steel clamp bar is more or less mandatory. Holes are drilled at 1.5″ intervals for the fingers. I chose 5/16″ bolts to hold everything together because I have way too many 5/16″ bolts. The main clamp bolt is also 5/16″ and runs through the entire base assembly. Fingers are made from hardwood.
Despite my best attempts, the finger mounting holes aren’t too accurate. This isn’t a huge problem because those bolts aren’t heavily loaded and they don’t all have to be installed.
Fingers are different lengths. The idea is you’d mix and match them as needed. Holes are threaded to accept 5/16-18 bolts.
Clamp bar in place with the fingers in their “default” positions.
One nice thing about this design is that I can replace things easily. If the clamp bar is too weak, I can just slip a thicker one on. Same for the fingers- I’d like to replace them with proper metal ones some day. Different widths and profiles can be made as needed.
Handles are the last part to go on. I need them to be removable, so they are bolted on. I used some 1/2″ square tube stock. Mine are about 24″ long, which is on the big side. 18″, or even 12″, would probably work just as well.
Handle on top for scale, handle installed at the right. I only had space for one bolt, but it’s holding up fine.
Retrospectively, the steel angle I used is a little too small. 1.5″ or 2″ would have been easier to work with. As it stands, I’ve got just enough to do what I want.
UPDATE:
I was a little worried that the single screw holding the handle on would not be adequate. Everything worked for a bit, then I pushed things a little too far:
You can see how the metal got pulled out into a little bulge. This implies the screw failed late, and it took a lot of force to break it.
The screw itself is pretty beat up. You can see the threads got ripped off. It’s bent too.
Repairing this was not possible. Instead I drilled out the holes to allow a 1/4″ through bolt. There’s just enough space to make it work.
If the hinge screws fail, I will have no real choice but to upgrade the leaf to a larger angle width. If the handle fails again, I’ll also have to upgrade. Perhaps I should do that preemptively.
As for how I broke it? My (brake) fingers are slightly too long. They get in the way of the leaf during a sharp bend. I’ll have to trim them down just a bit more.
Using the Box and Pan Brake
I think it’s fairly obvious how a bending brake works. Put metal in, clamp, pull lever. No need for elaborate text when a handful of pictures will do:
Clamp down for the first bend.
Reposition for the second bend. Note the relief notch.
Pull the lever.
You can see the test piece on the right. The others are tests I did while building the brake. Pretty good for something knocked together out of junk!
Looks good to me.
Finishing Up
Slide this one into the “why did I wait this long” file. I’ve struggled with metal forming for a while now. It takes a lot of skill to make good bends by hand- skill I just don’t have. Using a brake is so much easier.
Despite the rough appearance, this brake has proven to be accurate, strong, and easy to use. It is by far the best design I’ve come up with. Unlike every other attempt the workpiece stays put, even when the clamps are finger tight. Only the workpiece bends when you pull the handle.
I estimate the total cost of this brake at 50USD or less. Significantly less if you can find some bits for free. Time to build is maybe a few hours. The only specialized tool used was a 5/16-18 tap, which isn’t strictly required. When the cost is that low, I start to wonder if buying even a cheap cornice brace from Harbor Freight is worth it. For once the economics is clearly in favor of building your own.
An all-steel brake would be better. Casual examination shows that most professional brand brakes are blatantly just standard steel stock welded together with a coat of paint and a logo slapped on. Welding equipment is required, which is why I didn’t try this. Other people have, with excellent results.
Box-and-pan brakes can do a lot more than make boxes and pans. With the right fingers they can do some very complex work, including work that would be done on other (more expensive) tools. I don’t know how much this design can handle, but I can quickly slap together accessories to try them out. If something breaks I can just replace it.
Right now I have to use a wrench to operate the main clamp bolts. Proper knobs are definitely on my to-do list. Adding a crossbar to the handles would also be very useful for some bends. All very easy to add later on.
May and June turned out to be tough months for me this year. I just haven’t had the opportunity to finish any projects. Getting this done is both enabling and motivating. Finishing my brake allows me to start making progress in some other projects.
Such is the cycle. I’m sure you’ll be seeing this again in the not too distant future.
Have a question? Comment? Insight? Post below!