The Grind Stone is used as an alternate way to pulverize items into dust such as the following: Glowstone (4), Quartz(), Iron( ), Gold( ), Obsidian (1 Pulverized), Charcoal (1), Ender Pearl (1), Titanium (1), Chrome(1), Electrum(1), Tungsten(1), Lead( ), Zinc(1), Brass(1), Steel(1), Platinum(1), Nickel(1),Thorium(1), Plutonium(1), Copper(1), Tin(1), Bronze(1),Wheat(2), and Silver(1).
I In Blood 'n Bones it can also be used to mill wheat into flour.
Place on the ground and right-click on it with the Wooden Crank which is placed on top of this machine. Then place one of the items listed in the slot above and right-click the crank to operate.
Note: It is impossible to right click the Wooden Crank via automation, such as Turtles.