During the sale of our home, inspections recommended replacing a window with a broken locking mechanism. The window and its parts are no longer made, so I had to 3D print some replacements to avoid the large expense of replacing the whole window.
I've read that dowel joints are nearly if not as strong as mortise and tenon joints. The mortise and tenon joint requires expensive tools (specifically a table saw and a router) and the know how to make them, but dowel joints can be made with just a drill. The tricky part, though, is getting your dowel holes lined up on each piece. With my dowel jig widget, you can configure a jig for your specific situation and 3D print it at home or for an affordable price online.
I designed and 3D printed a gear shifter for my car. An engineer experienced with direct metal laser sintering wanted to to make his own out of titanium. In exchange for the model, he made me one as well. Read about how I barely managed to tap threads into it and see how you can do it yourself in a stainless steel version.