Tried the arm. The bucket's centre of rotation was not at the pin, so I put it there. Logical. I left a hole where I should have had a pin. When I was trying the imports, I had no idea of what would happen, and actually ended up with everything as one item, not knowing about ungrouping. This would only happen with 3ds, so I was not sure of what I should include in the imported object at all. So thanks, dukduk.