Boolean operations with flipped meshes

Hello there! I’ve been working on a character model and have run into a bit of a snag.

I created each major body section one at a time (arm, foot, leg, torso) and for the ones that normal people have two of, I duplicated them and flipped their scale on one of the axis(es?) in the transform window to make it a reverse copy for the opposite side.

Then I began to add things together using Boolean “union.” However, the items that were made by duplication and flipping didn’t combine with the items that weren’t. “Oh,” I thought, “I need to recalculate the normals!” so I went into edit mode, ensured all of the vertexes were selected, and recalculated the normals outside, as they are for all the other meshes.

…But that didn’t work either. Everything adds together fine except these meshes.

So, can anyone help me figure out how to add these? Or, how to flip the meshes in such a way that Blender thinks they were originally created that way?

Thanks so much in advance!

I’ve had similar problems, and at least most of the time I’ve been able to fix it by flipping the normals (rather than recalculating) as the very first thing that I do after mirroring or scaling by a negative amount.

That worked perfectly! Thank you very much sir!

And, should anyone come across this message with the same issue, I’d like to point out that flipping the normals and calculating them inside/outside are not the same thing. In edit mode, select all (Press the A key) press the W key, and select “Flip Normals.”

ther is a mirror modifier that can do what you did there in one shot
and may be faster also