Bolt

Sources

4 at a time in a Student's Casting Box, and requires 2 minutes to cool. Requires Fine Casting
40 at a time in a Master's Casting Box, and requires 4 minutes to cool (10 iron and 10 beeswax). Requires Fine Casting.

Found under hardware menu in either casting box.

2 needed to assemble a Essential Macerator
4 needed to upgrade a Chemistry Laboratory Level 1
6 needed to upgrade a Chemistry Laboratory Level 2
10 needed to add a Clay Dredge to a Raeli Oven
16 needed for installing a Water Filter in a Aqueduct Tower
24 needed for a Ka Vice
25 needed to build a Offering Vault
25 needed to build a Limestone Auger
25 needed to build a Small Steam Engine
40 needed to upgrade a Automatic Sawmill
40 needed to build a Chemical Bath
40 needed to upgrade a Small Warehouse
50 needed to build a Medium Steam Engine
50 needed to build a High Pressure Steam Engine
50 needed to build a Large Steam Engine
100 needed to build a Steam Shovel
variable amounts needed for the Strengthen the Mechanism upgrades for a Raeli Oven