I've been doing this for years, but Saturday someone saw it and thought it was a good idea so I'll share it real quick. I get 1/2 or 5/8 fine thread bolts, cut the heads off and use them as hole saw arbors on my mill or drill press. No need for a guide hole when the work is clamped, and it holds the hole saw rock solid for exact hole sizes. Works real well when coping tubing as well. Also, if you've ever stripped the threads in a holesaw, just weld a nut to it and keep it going. For a few bucks all your holesaws can be on their own arbor ready to go. Will it change your life? Um, no. Just dumb and simple.