[cnczoner]

I need to make about 100 pcs of this part (attached), and need it ASAP, so want to do this myself. The part is made of 0.5" wide strips of 0.090" 5052 aluminum (which I already have). It's about 2" across with ~1" arms and 2 holes.

I have a drill, drill press, jig saw, good chop saw with carbide blade for aluminum, and a CNC mill. But I don't have a bending brake. I do have (if I can dig it up) a vise-brake like this, but in the past I've found that it breaks 0.125"-thick aluminum because the bend radius is *very* sharp. Haven't tried it with 0.090" yet, because I have to find it.

Either way, I'm looking for a way to make some type of jig that I can use to make these repeatably (ie: so it's a task rather than an art). I don't mind buying a tool (say $100?) but so far all the Harbor Freight & Northern tool offerings don't state they'll bend 0.090" aluminum. But this thing is easy to bend by hand or with a pair of pliers.

Perhaps I can just make a block that would be the same width as the inside width of this part, then just clamp the metal onto that, and using a glove just bend the metal around both sides the block. Should I drill the parts first? Then I'd also need to make a jig onto which I can clamp the part so it can be chop-sawed.

Any better (simpler) recommendations? Thanks.

[doorknob]

I'm not sure that I can recommend anything better than what you're already thinking of doing.

I have only limited experience bending 5052 aluminum - in fact, IIRC it was 0.125" thick, and I bent it by clamping it into my vise and then hammering it with a dead-blow hammer. It was hardly a precision job, though. I don't remember any cracking, probably because the bend radius just wasn't all that sharp.

I'm not at all sure that I'd want to do 100 of them that way, though.

I remember that the material was pretty 'gummy' when I drilled holes in it.

How critical are the dimensions (including the distance between the holes and the bent edges)? If the hole locations (compared with the bent edge locations) are critical, then I'm not sure that you can achieve that with predrilling and then bending unless you can build a jig of some sort - I can imagine building a jig that has two dowel pins in it to match the holes, such that you could cut each piece to length, predrill the holes, place the piece over the pins, somehow clamp the piece in place, and then bend the two side pieces (even by hammering them down).

Alternatively, IIRC the HF bending brakes that I have seen are rated for their bending capacity in terms of a certain gauge of steel, and that rating probably implies that the material to be bent has a substantial width, whereas the width of your brackets is pretty small by comparison, and it should be much easier to bend the aluminum than the steel, even if the aluminum thickness is substantially greater than the rated steel thickness. It might be worth taking a sample of the aluminum into the HF store and giving it a try. Even with a bending brake you may have problems getting an accurate and repeatable bend because the brakes may not have material stops or other methods of accurately positioning or aligning your workpiece for each bend, but maybe you can do it OK if you're careful. But I can't think of a good way of aligning the holes while doing the bending.

[cnczoner]

See, I was expecting some major revelation in fabrication processes

I use/drill 5052 for other reasons and not found it to be gummy. Holes should be about +/-0.008". I don't see an issue in drilling those accurately before bending, but after bending I'd need to ensure the jog holds them consistently.

So when I posted that, I was intending to bend, bend, drill, then cut both arms of each piece simultaneously so that they're even. Or drill, bend, bend, cut. Because of the need to really secure the part properly if cutting arms after bending, I'd like to cut first, but then I'd have to figure out bending so that they're exactly the same length. It's okay if the arms are off by 1/16" or so, but both need to be the same.

Yeah I wondered about the same thing -- that a 1/2" wide piece should be bendable easier even if the brake doesn't say 0.090", but it would depend on 2 things -- being able to fit in the "slot" that the brake has, and that the brake is strong enough that I'm not bending/wearing the edge where the 0.5" metal is placed. I'd also need to see if once I bend one leg, there is clearance for the other leg to be bent. Ideally, I'd like to stack a few pieces side-by-side and bend in one motion. Like the try-out idea though. Will have to go there tomorrow when the temps go up a bit.

[doorknob]

If you made the jig out of steel, with the two dowel pins sticking up, you could conceivably make a "die" of sorts, also out of steel, that you could press down onto the jig with a small hydraulic press (or perhaps even an arbor press) - maybe the die could include a spring-loaded pressure plate that would first press down on the part before arms on either side would bend the sides of the workpiece down. The 'die' would be U-shaped, with the points of the U pointing downward toward the jig, and with the pressure plate in the center of the U, if that makes any sense. You would probably need some guide rails to keep the whole thing in alignment.

I'm not very good with drawing on the computer or else I'd try to put together a diagram. I think that it could work well enough that you would not need to trim the brackets after bending, because the dowels would precisely align each piece in the same position. It might take some trial and error to begin with in order to determine the ideal pre-bending length of the workpiece, but once that was done, each subsequent bend should be precise (at least, that's the way that it works in my mind - it doesn't always work that way in the real world).

[cnczoner]

Okay, I've revised so I'll now cut first, drill, then insert in to the jig (pic attached) and hand-bend (with large thick garden glove). I'll test first to ensure the holes aren't stretching.

Steel is the way to go, but not easy for me to work with. So I'm thinking I'll make it out of aluminum and recess a 0.5" strip of metal on the bottom half of the jig where the aluminum strip would rest. And if I recess that steel a bit lower than the aluminum, it would serve as the guide rails you're mentioning. I'm wondering though, if the dowels would be enough to align the parts... but only if I make a proper drilling jig so that the holes are quite accurate.

As for pressure, I'm thinking I can make the whole jig longer, then locate the pins closer to the back where the hinges are. Then I should be able to get enough pressure by just pressing on the front end. Only other thing to consider is that I may have to taper the sides where the aluminum strips rest, so I can overbend past 90-deg, so it springs back to 90.

Thanks.

[doorknob]

I'd imagine that something like that (with the pins moved closer to the hinge) would do the trick.

Looking forward to seeing your actual results.