I was careful to keep a slight interference fit on the alignment nibs in their housing slots on the top half of the frame. I can now push them together and easily hold them in place with one hand. This is important because the next step is to lap the "front" face of both parts simultaneously on a flat surface using increasingly finer grits of sandpaper from 80 grit to 600 grit. I designed the frame to work this way on both the front and back. As I lapped, I was careful to keep changing up how I held them and keep doing circles and figure 8's on the abrasive paper so as not to lap more metal off of one side and lose parallel from front to back. This didn't take more than 20 minutes to bring up a great surface that just looks terrific. I stopped at 600 until the whole unit is built because of the scratches I'll undoubtedly get from some of the other work.
|Top and Bottom frame parts lapped held together to 600 grit|