I am trying to find the formulas for making bends in sheet metal. I understand there are formulas for bend allowances. My issue is how do I determine where to bend if I want the inside dimension to be an exact number and if I want the outside to be an exact number. For both of the below questions the material is 6061 aluminum .080 thick with a .1 inside bend radius and 90 degree bends.
For example for the picture I included. If I wanted the piece to be 7" on the inside and the sides to be .5" I would do 7 + .5 + .5 + (2 x bend allowances) to get the total length of the plate I think? but how do I know where to put the bend lines to get 7" exactly on the inside?
Also on a totally separate plate how would I go about getting the total length of the unbent plate plus how would I know where to place the bends for an outside measurement of 7"
This seems like it might be so trivial but I just can't seem to grasp what is going on.
To clarify it would be 7" between verticals for the first one and 7" on the outside of the verticals for the second one.
This is not an exact part I need. It is an exercise in how to determine the lengths needed for what I am asking for. This information seems to be harder to find than gold.
Edit: I have read How do I size metal plates to get the correct dimensions after folding? and still don't understand. How does bend allowance and bend deduction help me. I am confused as ever and also extremely new at this.
I have done a little bending on my brake and seem to have something so please clarify if you can.
On a piece where I need the inside verticals to be exactly 7" I drew a centerline and measured 3.5 + .05( half of radius) from center and drew a bend line. Did same on opposite side. It seemed like I got 7" but it could be just luck.
Also on a piece where I need exactly 7" on the outside of the verticals I drew a centerline and did 3.5 + .05 - .080(thickness of the sheet metal) from center and seem to have gotten 7" on the exterior verticals.