Good Afternoon, I am required to make an "L" shape, with a 90° curved lip. As you can see in the pics; I am having an issue at the 90° part of the "L", where the lip just kinks wierd and wont curve nice. What is the solution aside from cutting it? Thanks!
Cut a "V" in the bent flange part. Make the bend. Weld the now-closed-up "V" cut. Lynn ***Added later** if you need to make a sweeping curve you may need to make a couple or several "V" cuts or slices to allow a more gentle curve rather than just a sharper bent corner. Or, you could cut the part that needs the curve a bit long, cut the flange part to the desired radius, bend the "tail" that needs the curve into place, weld the seam and Bob's your Uncle.
Make a wooden "Buck" to the shape you want. Then make "Tucks" and flatten/form it with a planishing hammer The soft surface will thicken/shrink the material [hitting between 2 hard surfaces will thin/stretch the material] It will require a lot of effort. The other method is to heat the material while clamped and try and hammer it into itself [this will shrink when cooled]
A shrinker/stretcher won't make a very tight bend in the "L" shape, its more of a curve with a 2" radius. If you need a true, sharp, 90 degree bend, cut and weld is going to be the best choice. If that 90 doesn't have to be real sharp, other methods (like the ones above) might get the job done.
Best advice... make friends with a tin-knocker. My dad was good at stuff like that,. no fancy tools either. I try to be on good terms with people I can rely on for tough tasks like that, it does go both ways if someone needs something machined or fabbed, I'm right there.
As stated above that's a tucking job. You want the tucks to pull the wide portion in tighter than what you want to start because as you shrink them it will want to pull back. The tucking effort will be substantial as I see it's also a doubled return lip. Google the term "sheet metal tucking" for a brief tutorial. I too recommend some sort of buck or shape to hammer shrink the tucks in to. Last bit of advice, hold the hammer handle where it is designed to be held to control the hammer blows. Don't choke up on it, let the weight of the hammer head do what it's meant to. You gotta feel that one on your own. Make a single layer practice piece to find your mojo. Show us how it comes out.
My amateur way when doing repairs on my truck where I could not get a decent panel was to look for a metal piece that had the bend or radius that I needed. I cut a similar piece off the drawer from an old stove. I saved the metal panels from anything I could till I had anything that needed fixing. Sometimes it is easier to weld a small premade piece to allow you to use a larger panel rather than try to fabricate it as one piece.
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