Clockwork Knights, Clockwork Bishops, and Clockwork Rooks will not respawn, nor will graves after being dug. But the caves can be reset witch contain graves and and broken clockworks. Therefore Gears are a renewable resource in the base game.
Downloadable Content
In the Reign of Giants DLC, renewable Tumbleweeds have a chance to drop Gears, thus making gears renewable in this DLC. Also, there are significantly more Chess biomes on a map, including some with Gears lying on the ground, making Gears much easier to get.
In the Shipwrecked DLC, Floaty Boaty Knights drop Gears, thus making gears renewable in this DLC. These are currently the only reliable source of Gears in this DLC. Each Floaty Boaty Knight drops one to three Gears. There is also a small chance of obtaining Gears from digging Sandy Piles, using the Slot Machine, or digging up X Marks the Spot chests spawned by Message in a Bottle. Gears can be used to craft the Quacken Drill and to restore the durability of the Iron Wind by 25%.
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