Grainger has Starrett Bi-Metal hole saws. The 5" is $50.00, and the arbor is $14.00. I bought mine at Home Depot for a bit cheaper than that. Home Depot (By me anyway), stopped carrying the Starrett brand, and started with Greenlee saws. They're Bi-Metalic, and seem to work just as well as Starrett. Lennox is good too. Don't run the saw too fast, especially the 5". That might be why those guys were dulling them out. I have my saws many years, and have drilled through all kinds of stuff. I haven't wrecked one yet.