Instructables

Step 7: Make the Supportive Eyepiece

Since the larger gear will be rotating, we need to keep it from hitting the skin on your nose or cheek, otherwise... rip! And you skin will tear.  

I found a piece of bicycle tubing that fit the edge of my aperture perfectly, so I decided to cut off a good 11/16".  You can round up or down, depending on the structure of your face.  Make it long enough so that the gear will fit comfortably.  

Note: Notice how the ID of the tube isn't small enough to overlap with those little circles on the aperture. This is CRITICAL!  Those circles are actually pegs that rotate in holes.  If you're going to super glue the tube to the aperture, you need to make sure that the super glue won't go into those holes!

Now, we're going to carve part of the tube out so that the tube isn't just jamming into your face.  I tried to trace out all of the parts of my face that were coming in contact with the tube while holding it up to my face.  Then, I'd go over to the belt sander and go at it until I thought I was done.  This was an iterative process, so I'd say just go for it.  If you mess up, you always have more tube!  The largest grind that I made was to accommodate my brow.