grindstone
nounUK /ˈɡraɪndstəʊn/
US /ˈɡraɪndstoʊn/
A grindstone is a round stone that spins and is used to make tools and knives sharp.
The old man pressed the blade against the spinning grindstone until it was sharp.
OTHER MEANINGS
2. A hard stone used in a mill for grinding grain into flour.
The miller replaced the worn grindstone so the wheat would grind evenly.
3. A source of hard, repetitive work or effort.
Years at the grindstone finally paid off when she earned her degree.
4. A revolving stone wheel used in manufacturing to polish or shape metal and other materials.
Sparks flew as the worker held the metal part against the grindstone.