As I write this section I realize that I failed to get any pictures of how I cut out the middle of these frames. I will make an effort to get some images in the future. For now, let me say that I used a pneumatic nibbler to cut out the center holes. A pneumatic nibbler is a tool that has an air pressure driven piston that moves up and down to cut our crescent moon shaped bites or nibbles from a piece of sheet metal. It's pretty tough to cut 0.050-inch thick aluminum sheet using hand snips. I considered buying a hand-powered nibbler but found a pneumatic one at Aircraft Tool Supply (ATS) while checking prices on hand-powered ones. Went to You-Tube and found a video of a guy demonstrating it's use and I very quickly decided that I wanted one.
Image 1 shows me filing the inside edge of one of the frames. The frame is held firmly to the table by a left over piece of the poplar I made the orginal lens form from. It holds the frme securely to the table and helps me file a straight line. Images 2 and three show how the frame edges are progressivly files smooth and straight,
Using my Vixen File to Smooth out the Nibbled Edge
Nibbled Edge Ready to be Filed Smooth and Straight
