You need a sheet metal brake.How does one go about getting sharp, crisp corners on simple sheet metal bends? I have some magnetic jaws I use on my vise and a sheet metal bending tool I got at a big box store. They all have larger bend radii than I'd like. I've bent 18 gauge and smaller.
You need a sheet metal brake.
Yep. The only easy way to get tight corners on light gauge metal is via an apron type brake with the upper clamping leaf having fore and aft adjustability. That allows the clamping point to be moved to within one stock thickness of the bend axis which gives you a near zero inside radius. By moving the clamping leaf away from the bend axis it's possible to make larger radius bends. This type brake is much more versatile and faster than any press brake when making one off parts or just a few bends.
Press brake dies come in 2 flavors. Air bending and bottoming. Even if using a dead sharp upper die (impractical) the bend radius in air bending will depend almost exclusively on the lower die opening width. 90° bottoming die sets can't compensate for springback, so once the press opens the resulting bend will be a bit less than 90°. For a variety of reasons, bottoming dies are only used in a relatively small percentage of press brake work. An upper die with a small nose radius can be used with a urethane block lower die to make an inside bend radius approximately equal to the upper die's nose radius. That's a popular method for maintaining tight corner radii while avoiding the expense of purpose built die sets to produce a specific angle and corner radius for a specific thickness of metal.
Good sheet metal parts designers need to have good knowledge of what's achievable with standard tooling because simply picking corner radii out of the air can result in a relatively simple part costing several times the price of a similar but well designed part.
I think you mean a 90° die results in a breaks greater than 90°, yes?
I'm not currently bending anything in particular; I mostly work with 16 Ga or less. I thought I might have to use some sort of upper and lower die set-up to get what I want, but asked to see what others would propose.
I don't need any particular radius; I just wanted to get it as sharp and crisp as possible. I thought there might be a way I didn't know of to do this with less expensive tools than a press brake. 16 Ga is too think to bend on these at anything wider than a few inches, but I do occasionally have a need to make something out of 16 Ga.
I might have room for one of those 3-in-1 brake/shear/rollers, but 12" is not quite wide enough and 30" is too wide, though I have made items longer, just at work. But I no longer have access to the sheet metal tools at work, since I switched jobs. A 24" one would work, but those are really hard to find. Bolton Tools has one for $652 (#SBR2420). I found an older HF 30" one on CL for $400, but I can get a new one for that. I might have to just go with a 30", especially since I've needed that wide before.