You need clean, uniform cuts in duct with minimal surface distortion. Sounds like you need the pipe duct cutter. With rugged steel blades and a reinforced spring, this tool cuts through up to 18 ga sheet metal and 22 ga stainless steel with ease and leaves a professional finish every time.

hilmor® Pipe Duct Cutter, 10-1/2 in OAL, Black and Green Handle, 3 in W x 7/8 in H

• Rugged and durable - high carbon steel blades and a reinforced chrome silicon spring increases life and durability
• Comfortable grip - over molded handles reduce hand fatigue and won't slip or twist

• Catalog https://assets.unilogcorp.com/267/ITEM/DOC/Hilmor_1839020_Catalog.pdf