Miner (Maintenance - M5) was with Manager of Fine Grind/Mill Operations and was attempting to cut thru a piece of conveyor belting. Miner had noticed his work utility knife had a dull blade, and upon changing it with new one, was cutting belt when knife skipped/slipped and cut his right lower leg. Miner was transported to OCCU-MED and 4 sutures were used to close small laceration.