I have read in several different post-apocalypse novels of the survivors using old house keys for arrow head blanks. So I decided to give it a try and see what the results would be.
Step 1: Tools to use
To mark, cut and shape the keys into arrow heads, I used a black Sharpie marker, jeweler's saw, double cut file, jeweler's bench pin and two C-clamps. Clamp the bench pin to your work table with the keyhole shape facing you.
Step 2: Mark your planned cuts
I drew a line from the outermost edge of the key to just below the key ring hole. Be sure when you start to cut that you cut to the INSIDE of the marked line. This will save you a lot of file work later.
Step 3: Making the cuts
Make each cut along your lines. Done properly as noted in Step 2, this will leave you a fairly sharp point. Cut on the down stroke. This gives you the most control. The waste metal should come off in one piece.
Step 4: Filing the edges
Start filing a sharp edge. Do both sides of each edge, starting on one side, then flipping the new arrow head over to do the opposite side of the opposite edge. Repeat for the second edge and second side. Be sure to keep the edges even, and all edges meeting at the tip.
Step 5: You're done!
Now all you have to do is mount the new arrow head to a shaft and see how well they fly.
Think about basic safety, as these WILL easily penetrate skin and animal hide. Only test on suitable NON-LIVING targets.