Step 5: Making the "Glass Clips"
Once cut to size, the blanks were sanded on one outer face and both edges with a 220-grit belt on the sander. This may not be necessary, but it makes them look nice. All edges and corners are then knocked off with a few swipes of a fine-tooth file.
I set up a jig on the drill press to allow drilling the holes quickly and accurately. I highly recommend using cutting oil or WD-40 to lubricate the bit every couple of operations - it will keep chips from sticking to your bit, result in cleaner holes, and keep you from having to stop so often to clear chips or shavings from the drill bit. A small plastic measuring cup with a small amount of lubricant works well - just dip the tip of the drill in every other operation, and it will all go quickly. Lubrication is doubly important for the countersinking operation - you'll get some pretty terrible looking results without it - the aluminum will tend to "smear" more than shear.
After drilling the holes, you'll want to countersink them so that the heads of the screws you plan on using are flush with the face of the angle as shown in the picture. Once again, I used a cutting lubricant (WD-40), but in this case I used a hand-drill as it allowed me to rock the bit a little to get a cleaner hole. I think I need a new countersink bit ;)
Once you've sanded the faces and edges, and drilled and countersunk the holes, you'll want to wash the clips thoroughly. You could use anything that will cut through the oils and lubricants you've used. My preference is Simple Green at full concentration - it does an amazing job of cleaning all kinds of contaminants off of metal, and doesn't leave a residue when it's rinsed off - and it's water soluble and doesn't eat up your hands. Good stuff. Try to avoid touching these pieces with bare hands until after you've applied finish.