Fabricating A Sheet Metal Bending Brake

April 05, 2012

The last five pages of the Sonex plans packet are labeled, “Basic Shapes”. Each page has a group of drawings on it, that refer to specific formed, aluminum shapes, that are used in different locations of the aircraft while building it. The typical shapes called for are; “channel” stock; “angle” stock; “flap” stock; and “aileron” stock.

Below are a couple of photographs, that will give a reader an idea of what the, “Basic Shapes”, drawing identification block looks like.

Here are a few photographs that give a reader an idea of what kind of shapes I am referring to.

Each “Basic Shape” drawing, also has a “Cut List”, of the given shape, printed right next to it.

For example, the Cut List for the 1” x 1” angle listed above, looks like this:

The Cut List for the “-04” .025” Channel Stock looks like this:

Here is the Cut List for the “-02” .032” Rear Spar Channel Stock:

Each Cut List, will tell a builder how much is needed of each Basic Shape, and where that length will be used during the airplane’s construction. Each Basic Shape piece has a length measurement, a quantity amount, and a “drawing destination” listed next to it, within each Cut List.

Take a closer look at the Cut List for the .025” Channel Stock; particularly down towards the bottom of the list. There is a length listed of, 77” long.

Now, take a look at the Cut List for the .032” Rear Spar Channel Stock. You will see listed, two 96” long pieces that are needed.

The question I had was, “How am I going to make all of these Basic Shapes?” I fiddled around with a few ideas of my own, to get a “feel” for what it was like to bend aluminum into these shapes. I also studied videos on online, and looked at some ideas other builders have come up with to deal with this situation.

The shorter lengths of stock, could be bent using a sheet metal bending brake; either purchased, borrowed, or home-built. Ultimately though, the three long lengths of channel stock, (77” long, and the two pieces at, 96”long), had to be dealt with at some point. That meant finding a way to accomplish this task.

I have been told that a contractor’s aluminum siding, bending brake, does not have the strength to handle bending, .032” thick 6061-T6 aluminum. That is unfortunate because, that piece of equipment is usually manufactured in a 10’6” length. Which, would be perfect for the Sonex! And often, used siding brakes can be found for sale, or rented from a siding contractor.

There are a couple of “home-built” bending brake designs, that are popular with scratch airplane builders. The price for the material runs about $75, so the cost IS fairly “cheap”! One of those popular home-built bending brakes, incorporates the use of a workbench. The bending brake is mounted along the edge of a builder’s workbench. Although this bending brake design is effective, efficient, and inexpensive to fabricate, I chose not to build one for the reason that it WAS mounted to the edge of a workbench.

I made the decision that I wanted a standalone bending brake. I wanted a sheet metal bending brake that could stand by itself, and would not be a part of my workbench. I also wanted a sheet metal bending brake that was long enough to tackle the longest bends needed for building the Sonex. I wanted to be able to use it anytime that I wanted to, (I didn’t want to borrow a bending brake, or rent one). And, I wanted to be able to bend material that was much thicker then the .032” aluminum; being able to use the bending brake for future projects. Finally, I wanted my bending brake to be designed and fabricated, so that I could dismantle it, and store it away if I wanted to.

What follows, is a journal of photographs, and written text, that will walk a reader through how I made my own bending brake. Its design is based on my “wants” that I listed in the previous paragraph. And, I will tell the reader right up front that, the materials to build my brake cost nearly $500. So, it isn’t cheap! But, it DOES do all that I set out to make it do!

Here are the sketches, of my bending brake design, scribbled out on my “idea pad”. I am not much of an engineer! Nor, an artist! But, this is all that I worked from to build, “The Beast”.

I borrowed a pickup truck from a good friend of mine, and drove to, Bangor Steel, located in, Bangor, Maine.

I had phoned in advance of my arrival, and ordered the material that I wanted. I do not know much about steel. I did some online research. Using the web as my resource, I studied different profiles, and sizes of the material, to inspire the sketches illustrated above, and to arrive at a materials list.

Here are two photographs of the interior warehouses of Bangor Steel.

Here is the bill that I paid. The total was $361.45.

I loaded up the pickup truck and drove home.

And, I unloaded the steel on to my garage floor.

The 4” wide channel stock was going to be used for; feet, legs, stretcher, bed support, and bed. Those pieces were the first for me to cut up to size, so I organized the channel stock on my workbench.

Using my 4” grinder, with a metal “cut-off” wheel tightened on to the arbor, I began whittling my way through the channel stock; cutting the lengths that I needed for my bending brake.

Below is a photograph of all of the parts that make up the supporting structure of my brake.

And, here is a photograph of my supervisor. His name is, “Reuben”. He is an 8 year old Black Lab; 103lbs and with only three legs!

As I previously mentioned, I wanted to be able to dismantle my bending brake. To be able to do so, I had to bolt it together so that I could unbolt it later if necessary. Below, are several images that illustrate me drilling and bolting various parts of the brake together.

Here, a reader should get the basic idea of my design now.

Under the ever watchful eye of my supervisor…….

The next series of photographs will show me drilling and fastening, what I call the “bed” of the brake to the supporting structure.

Pilot bit.

Clearance bit.

Here, I am countersinking for the head of the bolts, that will be used to fasten the bed to the structure.

Tightening up the “bed bolts”.

Here I have laid out the 18 hinges that I used to attach the bending leaf to the bed of the brake.

Before using the hinges, I had to drill one new hole, on one leaf of each hinge, so that it would “catch” the edge of the bed.

The hinges that I chose to use are for woodworking. They are designed to be mortised into the edge of a passageway, or entryway door, and also into its related doorjamb.

I am NOT mortising steel! So consequently, I had to cut up some 1/8” thick steel shims; 36 of them to be exact!

A pile of hinges, and a pile of shims, ready to be pressed into service.

My strategy here was to mount the 18 hinges, (with matching shims), to the bending leaf first. The bending leaf is a piece of steel that is 6” wide, by 3/8” thick, by 8’ 6” long. Incidentally, 8’ 6” is the intended working length of my brake.

The hinges were mounted to the bending leaf by, locating the hinges, (proper spacing between each one), marking where the holes were to be drilled, threading each drilled hole with a 10:24 tap, then fastening the shim and hinge with 10:24, flat head machine screws.

All of the hinges mounted to the bending leaf.

In the photograph below, a reader will see the bending leaf clamped to the bed. I stuck a piece of masking tape to the edge of the bed. I did this so that I could better see the marks that I had to transfer from the hinges, mounted on the bending leaf, to where I needed to drill, and tap their mating holes, for the other leaf of the hinge, into the bed.

As I moved along through this process, I would unfasten the hinge from the bending leaf, and fasten it to the bed.

Here are all of the hinges now mounted to the bed. The shims for the bending leaf side of the hinges, are lined up on the floor.

Using C-clamps and a couple of buckets, I supported the bending leaf, right next to the bed, and fastened the bending leaf to the bed, using the hinges I had previously fastened to it.

And, here it is! It should start making sense now. I hope!

This is what the extent of the bending action looks like. I had planned to bolt a piece of 1” by 1” angle iron to the top edge of the bending leaf, to give it more leverage and surface area.

At this angle, the bending leaf is “hinge binding” against the bed. I knew that it would, but I had hoped that I would get more swing of the leaf, before it bound up.

I decided to “nip off” the inboard corner of the bending leaf, to give it a little more swing. I did that using my Circular Saw with a metal cutting blade tightened to the saw’s arbor.

In the next three photos, I am drilling, tapping and bolting a piece of 1” by 1” angle iron to the top edge of the bending leaf.

After that task was complete, I was dying to see if my contraption would work! I am holding in my hand, a piece of galvanized steel. It is thicker and stiffer then the aluminum I need to bend. I had quickly cobbled together a pinch bar with a 1/8” radius along one edge. I used C-clamps to “trap” the piece of sheet steel between the bed, and the pinch bar. I was excited by the results!

Now, it was time to make a proper handle for the bending leaf. I happened to have a length of black iron pipe left over from when I fabricated my buffing / grinding station. It looked like the perfect solution for the job!

I own a Harbor Freight, hydraulic pipe bender. I had purchased it used a couple of years ago, so that I could fabricate my own set of crashbars for my adventure motorcycle.

After I got the handle made up, I needed to “cope it” into the face of the leaf to that I could bolt it to the leaf. I used my woodworking skills and my grinder again to do that.

Not bad, eh?

I then drilled and tapped the necessary holes that I needed for bolting the handle to the bending leaf.

Next I needed a centerpost for the handle. One end of the centerpost needed to be notched to the radius of the handle, (called a “bird’s mouth”), and the other end needed to be notched, like the ends of the handle were, to fit to the bending leaf.

I used a holesaw to cut the “bird’s mouth” into one end of the handle’s centerpost.

I was kind of proud of this. One cut and a perfect fit!

Here I am marking out where the notch needs to be in the other end of the centerpost.

And, cutting that notch.

Then, drilling, tapping, and bolting the centerpost to the bending leaf.

By this time, I had used nearly every tool in my shop, except one. So, I broke out my Oxy/Acy torch set, and welded the centerpost to the handle.

Now, it’s looking like something!

At this point, I decided to make another test bend. The material that I chose to use this time was, a piece of 1/32” thick stainless steel. Again, I used my temporary pinch bar, with an 1/8” radius along one edge.

The final part, that I needed to fabricate for my bending brake, is the “pinch bar”. Because there is more room, and better quality tools available, at the boatyard where I work, I headed off there for the next phase of construction.

The photograph below shows me ripping a piece of ½” Corian on a tablesaw.

On one edge of the Corian, I routed a 1/8” radius, and on the other, I routed a 1/16” radius.

After the routing was done, I headed back to the tablesaw, and I “back cut” the Corian, at a 30 degree bevel; “sloping” away from each radius.

In the photograph below, there are three short sections of scrap angle iron, “nested” together, sitting on top of the Corian platen. The two bottom pieces will be 8′ 6″ long. The middle piece will be short sections, (“gussets”), that will be welded to the other two, longer pieces of angle iron. (This will make more sense to a reader, shortly!).

I packed up the Corian pinch bar platen, and headed back to my garage.

In the photograph below, I am cutting angle iron gussets, that will be welded to the pinch bar backing structure.

All of the gussets cut to length.

Here I am laying out the spacing for the gussets.

And, here I am welding the gussets to the pinch bar structure.

All of the gussets welded in place.

Moving over to my workbench, I slid the Corian platen underneath the pinch bar structure. I needed to bolt the Corian platen to the steel pinch bar.

Here I am bolting the Corian platen to the pinch bar.

Finally, it was time to give “The Beast” a test!

I laid out a ½” “flange line” on a piece of sheet steel.

Using C-Clamps, I “pinched” the piece of steel to the bed of the bending brake.

I lifted the handle……..

For my first, “calculated” bend, I was shooting for ½”. I ended up at 33/64”. I don’t think that is too bad!

To complete this project, I wanted to cut the pinch bar into two pieces. Adding to my list of “wants”, I decided to cut the pinch bar into a 3’ 3” long piece, and a 5’ 3” long piece. The two shorter sections will be easier to handle. When I need a longer bend, (77” and 96”), I can butt them together.

And finally, I added a diagonal support, from each leg, to each foot.

Here is my finished, sheet metal bending brake.

My next step is to, begin making some practice bends, on some scrap metal I have here, to teach myself how to use my new brake.

That story will follow soon!

Fluting Pliers, Deburring Tool, and Shears

One of the first hand tools that a homebuilder purchases, to construct their Sonex airplane, is a good pair of shears to cut shapes out of the aluminum sheets.

As I have mentioned in my other posts, I have no experience in handling, and working with sheet aluminum! And, I am guessing that I am not the only “newbie” to purchase a set of useless shears to try and cut the aluminum with. I tend to learn my lessons the old fashioned way; the hard way……

Here is a photograph of the shears that I currently have in my shop.

The set of three, color coded, matched shears on the left, are the ones that I am referring to as useless. They just don’t work very well at cutting .025″ thick aluminum. And, if they don’t work well on that material, they certainly won’t work very well at cutting .032″ aluminum sheet! My recommendation, from my own working experience with them is to, not waste money on purchasing shears like this.

The set of shears in the middle of the image work much better then the matched set. But they are old, and have a burr along the edge of one jaw. They are also somewhat “bulky” feeling to use.

The last set of shears, (the “red handled” ones, on the right), are an absolute delight to use! Because of the offset head, the jaws of the shears can rest on a worksurface; adding support, and carrying some of the weight, while I cut pieces of aluminum sheet with them.

The brand of the shears is, “Wiss”, and are designated by them as being 11″ long. The product number is: A10BSL

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After making cuts to sheet aluminum, with shears as mentioned above, or when drilling holes through the material, ALL edges need to be “deburred” before putting the part into use.

The edge deburring tool that I have chosen to use is a, Shaviv Mango II. The tool came with 10 replacement blades, and the “neck” of the Mango II can extend and retract into its handle. The design is intended for being able to reach difficult spots for deburring.

Here is what the Shaviv Mango II looks like.

I have deburred five forward rib blanks using the Shaviv, and it works very well. But, I have gone through two deburring blades to do it! That is not because the blades have become dull too quickly. It is because the tool rolled off of my workbench, (twice!); hitting the concrete garage floor, resulting in the blade snapping off.

I needed to make a way to hang the tool up when I wasn’t holding it in my hand.

I cut a short length of welding rod, and bent it to the shape you see below, being held in my hand.

Using a drill bit of the same size as the welding rod, I drilled two holes, on opposite sides of the cap, that forms the end of the Shaviv’s handle.

I snapped the welding rod “loop” into the cap. Now, I have a way to hang up my deburring tool, when I am not using it; resulting in increased blade life…..

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After a piece of sheet aluminum has been cut with a pair of shears, its holes and edges deburred of “roughness” with a deburring tool, there is a high likely-hood that the aluminum workpiece is going to be bent over a form of some kind, to create a new shape out of it. If that bending form is for a wing rib, the new aluminum shape is going to have curved edges to it. When sheet aluminum is bent along a curved edge, “ripples”, “puckers”, or “wrinkle” distortions form in the aluminum workpiece.

Below is a photograph of the flange, of a forward rib, being tapped down over the edge of the Forward Rib form. Because the edge of the rib has a curve to it, you can see “wrinkles” forming in the aluminum material.

The process of “fluting” the aluminum, tames the aluminum to the shape it was designed to maintain. Fluting pliers are used to do this, or at least, used to adjust flutes after they have been made by other methods.

Fluting pliers can be purchased, or made. I have seen photographs, and I have watched videos, of other builders working with homemade fluting pliers. Most all of the homemade fluting pliers I have seen, have been made from modifying a pair of “Vise-Grip” brand/style pliers. And, I have watched nearly all of the builders, of this style of homemade fluting pliers, struggle in using them! That is because, when the builder has come close to the final “squeeze point”, in using the pliers, the handles of the pliers “lock” together. This necessitates, having to “unlock” the handles of the pliers, to remove them from the flute. This doesn’t make sense to me!

To make my own set of fluting pliers, I purchased a set of heavy, spring-loaded pliers from my local Lowe’s store. By spring-loaded, I mean that the jaws of the pliers want to stay open. At rest, the pliers are open; the jaws are forced open by the spring mounted in the pliers jaws. To close the jaws of pliers, I compress the handles with my hand. When I release pressure on the pliers’ handles, the jaws want to open. A much more natural, and more efficient flow when fluting pliers are called for.

I cut three short lengths of 1/4″ diameter steel rod. I clamped the Lowe’s pliers between the jaws of my vise, in a way that would “trap” the length of steel rod in place, while I welded it to plier’s lower jaw.

I welded the other two lengths of 1/4″ steel rod, to the sides of the upper jaw. In the photograph below, you will see a length of welding rod crossing between the fluting jaws. I used that to help hold the side rods in place during the process of welding them.

Here I am doing some “test flutes”, using my new fluting pliers, on a scrap piece of aluminum.

After some adjustments to the steel rods, (bending them closer together),……

…….I am very satisfied with the results! And, they are quick and easy to use!

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Here is a photograph of, “Hand Tool Organization” underneath the edge of my workbench, where I can reach for them quickly and easily.

Modifying My Pedestal Vise

As I have begun to cut out, and shape aluminum parts for my Sonex, and work with some of the tools that I have made, or modified, I have discovered that I need to make a few more “adjustments” to some of them; rendering them more efficient in their use.

My Pedestal Vise is one of those tools.

I cut three short sections of 3/8″ diameter rebar, and bent them into “U” shapes.

Using my grinder, I prepared the underside of the pedestal vise’s “top plate”, for welding the three, rebar “U-shaped” pieces to.

I welded the “rebar hoops”, to the underside of the top plate. Their purpose is to hold the mallets I want to use, while fabricating the wing ribs of the Sonex.

Using a short length of 1/4″ diameter steel rod, I welded a “hook” to one of the legs of the pedestal vise.

I did this so that I had a place to hang my hacksaw.

During the original building of the pedestal vise, when I welded the three legs to the wheel rim, I am guessing that the application of heat, from the torch, slightly warped the rim. When sitting on a flat surface, the pedestal vise “rocked” a little bit. I needed the vise to be “rock solid” while working with it.

Using a cut-off wheel, mounted to my grinder, I cut the “high spots” off of both sides of the bottom edge of steel rim.

The pedestal vise now sits firmly planted on my garage floor. I also have a place to store my hacksaw, and hang the mallets that I need, to shape and form parts, to my airplane.

New Router

As I have been working with my Porter Cable router, that I picked up about two weeks ago, at my local, Home Depot, I have heard, and have felt a vibration coming from it. I have noticed a sound, and a feel that is much greater then it should be.

Upon close examination, (chucking up a 3″ long, 1/2″ diameter trimming bit in the collet), I could definitely see a “wobble” to the bit, and that wobble corresponded to the sound the router was making, and its vibration too.

With the router unplugged, I grabbed the motor in one hand, and the end of the router bit in the other hand, and wiggled the bit. I could feel a distinct play to the router motor’s shaft. I decided to return the router to Home Depot.

When I got there, (I was told that there was no problem in returning the router.), I discovered that the Bosch router kit, that I REALLY wanted in the first place, was now marked down as a “clearance sale” item. The price of the Porter Cable router was $149. At the time that I purchased it, the Bosch router kit was priced at $199. This weekend, the Bosch router kit was now discounted to $169. Close enough! I bought the Bosch router kit, and paid the $20 difference in cost. (Bosch 1617EVSTB. This is a router with two bases. One for the motor, and one to be mounted underneath a router table. Perfect!)

To use the new Bosch router, I had to modify my router table.

I flipped the router table upside down. Then, I positioned the auxiliary router base over the existing “pocket” that I had routed out for the Porter Cable router, and traced around its base.

Using the new Bosch router, I enlarged the “pocket” to the new pencil line.

I needed to mark where the new mounting screw holes needed to be drilled through the router table surface. Like the Porter Cable router, the Bosch had three mounting screw holes. Two were “exposed”; drilled right through the base. The third hole was “hidden”, in an area, where one of the handles attach to the router base.

To solve this problem, I ground the head off of a 10:24 flat head machine screw.

I then threaded the modified machine screw into the mounting hole that was “hidden” in the handle casing. I threaded the other two machine screws down through the base.

I positioned the router base back into the pocket. I lightly tapped the three places where the machine screws were threaded into the router base. Doing this, left three easily identifiable marks, in the pocket, where I needed to drill through the router table surface.

Once the new clearance holes were drilled from underneath, I flipped over the table surface, and countersunk the holes to accept the head of a 10:24 flat head machine screw.

I knew that the original bit hole was not exactly on center to the new Bosch base. I fixed that by chucking up a large “round over” bit in the router’s collet. I then inserted the router motor into the base of the router table, turned on the motor, and “wound it” up through the table surface; cutting a new, and centered bit hole in the router table.

No vibrations, or wobble to my new router table setup! It works very nicely!