I am starting a new project not entirely related to tractors but this site has such a diverse knowledge base. I figured I might be able to get some advice here. I am building an airplane out of aluminum. I bought a harbor freight bending brake to do most of the smaller bends. There are other techniques for bending thicker material using a shop press or an arbor press. The wings will be bent using a vacuum method. The part that I am not sure the best way to get accurate angles is with the 30" bending brake from harbor freight. The plans call for some radii to be 1/8", 1/4" 3/16 " and others 1/2". Most of the construction will be using 0.025" 6061 t6 aluminum.
I have tried to move the part back from the bend line to open up the radius. This works OK. Just looking for more consistent and accurate results.
Thanks
Mike
Well you are at the right place!
I am an A&P and taught sheet metal at local trade school.
Bending aluminum accurately is an art. Looking at a cross section, the outer 60% of the alu will stretch and the inner 40% actually shrink making very accurate bends tricky, so if accuracy is important you need to adjust your bend lines accordingly.
Now there are formulas to calculate bend radii for different metals but your plans specify them.
Generally a easy method is to make radius bars which is a strip of alu bent 90 deg and you simply use this between your brake and the work piece.
Example; using a 1/8 pre bent angle will give your work piece a 1/8 radius. and if you pre bend a second with the first , when paired you will be producing parts with a 1/4 radius.
The larger radii do pose more of a problem. If the parts are small (like brackets or clamps) you could always resort to using a vice and hand bending over a radius.
I occasionally use my bench vice and 2 lengths of angle iron (to widen the jaws) and form all sorts of smaller items.
T6 alu is 'stiff' and breaks easily and for sure needs a decent radius otherwise parts will fail.
Some hints; be sure to deburr all your edges as well as all fastener holes.
For nice clean straight cuts, forget hand sheers, use a straight edge and do a 'serious' scribe (hook knife is great) and fold it in your brake and then draw file for a perfect edge.
'nother tip. Never use a pencil to mark alu, causes corrosive reaction over time, fine felt markers are best.
Running your hand wearing a cotton glove along edges will tell you if your finishes are up to aviation standards.
Have fun, wish you were closer as I have all sorts of aviation tools and would love to be part of a project.
