A Bronze Gear is the moving part of the Factory’s machinery. At the Iron Anvil, one Bronze Ingot makes 3 (4 with the Gearmaster perk), with the Iron Smithing technology (50 red) and Smithing mastery 5.
It goes into the conveyor network: 1 for each belt, 3 for a splitter, 4 for an underground conveyor, and 2 to 4 for conveyor chests and the supply station. The Circular Saw takes 2, and repairing the Factory’s broken conveyor pins takes 4 at a time.