The next time you have to hole-saw metal, first hole-saw through one of those big yellow car-washing sponges. Leave the plug of sponge inside the saw and soak it with some cutting fluid. When you push the saw into the metal, the cutting fluid is squeezed out of the sponge, giving you a cleaner, faster cut that will preserve your hole-saw teeth. Store the sponge in a container with a tight-fitting lid, and reapply fluid when you use the hole saw again.
Justyn Clarke, North Dartmouth, MA