Can anyone here please give me a ballpark figure on the angle tolerance of 6061 structural angle? I haven't found anything with google. I have a piece of 2" x 2.5" x 0.187" 6061 T6 angle bent out of square. Photos at:
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It was part of an aircraft kit, and the kit manufacturer has said the tolerance is 5 degrees. Is that typical? All the aluminum angle I've seen is right to within a fraction of a degree. It will be a real pain to make this fit.
I bet it's been sheared in an angle shear. Have you tried to straighten it? I've never been there with aluminum angle but have with steel. Try the BFH.
Five degrees sounds awfully loose. Standard mill practice (AISC) for rolled steel structural angle is +/- 1-1/2 degrees. I'm afraid I don't have anything specific to aluminum structurals.
The picture shows that the inside corner is filleted, so it is extruded, or machined. Assume that it is extruded, to machine it would be a waste of time and material. Aluminum is hot when it is extruded, because it is more plastic, but also so that the material may be quenched or slow cooled, depending on the temper of product desired. It extruded at a high enough temp., it can be quenched and subsequently precipitation hardened to achieve the T6 temper.(usually costs more, product must meet ANSI H35.2 and so must be straightened by the mill when hard). If precipitation hardened later, it may be twisting in the oven and not being re-straightened. Usually aluminum used for flight hardware is controlled by ANSI H35.2. I don't know what the limits are, but twist is controlled on an inch of twist per inch of length basis, up to a max amount. In other words, one leg of the angle place on a planar surface will be zz inches off of the surface in yy inches. This is doubly constrained by the angularity tolerances, which I don't think will allow the twist tolerance to be exceeded.
Thanks for the info guys. This is definately extruded aluminum. Now I think it's been bent in a brake accidentally. The kit manufacturer bends some smaller 6061 angle to 88.5 degrees for some parts, and I bet they bent the wrong piece, because mine's 88.5 degrees. I'm told it's usually exactly 90, like the plans.
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