I’m delighted by the progress I am making on my DIY sheet metal bending brake. There will be a Part 3 and more before I am done, but here is progress so far:
The Down Clamp: Since writing Part 1 I have successfully fabricated the Down Clamp. This is the piece of 1/4″ thick, 3″x4″ angle iron at the very top of the brake. Any sheet metal to be bent slides under this clamp. The clamp is then pressed down to hold the sheet metal in place.
I should note here that I had to make a decision about how to hold the Down Clamp down against the I-beam. Most professionally-made brakes use a rapid cam-action lever. Very nice, but DIY fabrication of a cam mechanism seemed complex. And as I will use the brake only infrequently, I decided on a simple nut and bolt affair.
Back to fabrication of the Down Clamp: First, I made a notch at either end of the angle iron to make room for the hinges (I have already planned the hinges). Then with the angle grinder and a drill bit, I made a three-quarter inch hole at each end of the angle iron. Next I welded a five-eighths inch hex-head bolt upside down on the I-beam. I dropped compression springs over the bolts. Here is one of the bolts welded to the I-beam:
Then I placed the angle iron, with the big bolts coming up through the holes. I put nuts on the bolts and cranked the angle down all the way. As I predicted it might, the angle iron deflected upwards at the middle. Not much, but enough that the sheet metal would not be held firmly in place. I had already thought that a strengthening truss would be needed.
I unscrewed the nuts and placed a one-eighth inch spacer under either end of the angle, then bolted it back down. At the middle of the angle, I used a couple clamps to pull the angle iron down to the I-beam, thereby creating a very small center-downward arch to the angle iron. Then using five-eighths inch rebar, I went about fabricating and welding a truss onto the angle iron. When I was done, I removed the clamps and spacers and ta-da… the angle iron held its little arch. As I screwed the nuts down, the arch in the angle iron compressed and mated perfectly with the I-beam. I was not able to see any light passing between the angle iron Down Clamp and the I-beam and it firmly held a piece of paper everywhere under the clamp. I breathed a big sigh of relief and did a happy dance because this was one of two mission-critical parts of fabricating the brake. (The other mission-critical part is the pair of hinges.)
I finished the Down Clamp fabrication by welding on an adjustment bolt for aligning the front of the Down Clamp with the front of the I-beam. In the next photo you can see the Down Clamp front edge alignment bolt. The nice thing about this being adjustable is that for steel sheet metal, which can take a nice sharp edge, the Down Clamp can be set precisely just a tad (the thickness of the sheet metal being bent) back from the front of the I-beam. However aluminum wants a more rounded corner or it will crack, so I can back off on the bolt and the Down Clamp will move backwards a little bit more (thickness of the aluminum plus a whisker or two), giving more room for the aluminum to round over. Here is the front edge alignment bolt at the lower right corner of the next photo:
The Hinged Angle Iron: The next big part of the project is to attach hinges to the other piece of angle iron so that it can swing up and bend the sheet metal. This is going to be a delicate operation as the hinges must be positioned perfectly. If the hinges are even a fraction off center or a tiny bit crooked, the bending operation will be faulty.
Recently I spent a lot of time at the Discovery Center in Panama City, looking at hinges and also at things that are not hinges but could be if I thought outside of the box. All the hinges, dozens of different styles and types, had potential flaws. Most were not strong enough, allowing for stretching or bending of the hinges. Others were not accurate enough, allowing for slop to enter the process. Even others wouldn’t allow the alignment axis that I need. I’ve seen good DIY hinges on other peoples’ brakes, but I couldn’t find tubes and pins that would mate closely enough to make a good homemade hinge.
Finally it dawned on me. The LED light bulb above my head turned on. How about using a bolt with a bunch of nuts? If you put a bunch of nuts on a bolt and tighten them, the bolt won’t turn. But if you leave a small space between the nuts, the bolt will turn. Or more correctly for my application, the nuts will spin on the bolt. And the action is quite smooth and accurate. I picked a few parts out of a few of the hundreds of bins and started making mock ups. I settled on beefy three-quarter inch, three inch long bolts with three nuts on each bolt. I can weld every other nut (and the bolt head) to the two pieces of steel to be joined by the hinge. Here is a photo of my imagined hinge:
Next I will cut very accurate notches (to accept the hinge) in the I-beam and the angle iron, then weld the hinges in place.
But sorry, that will have to wait for another day as more pressing tasks are calling for my attention.
In other news: The front garden is doing well. The weeds are doing too well, but we are trying to have a ground cover, a pretty little plant with blue flowers, do battle with the errant morning glory weed menace. Here’s a garden photo:
At the far end of the garden we left a tree stump, and have been seeding it with bromeliads and orchids:
One of the orchids is in full bloom:
I’m sure that others will be flowering in due time and I’ll post an update.
That’s all for now. Thanks for stopping by.