Cutting 3 inch duct board

[JasonMTL]

I'm an insulator by trade. I spend most days cutting through 3 inch fiberglass duct board with a generic bread knife but they grow dull fairly quick. "duct knives" work too but they are made from low-grade steel that just refuses to hold an edge. Any ideas as to what I should be looking for? Any help is much appreciated and thank you in advance.