grindstone 磨石 ; 砂轮

【例句】
I'd better keep my nose to the grindstone if I want to finish the project on time.
如果我想准时完成这个案子，我最好继续埋头苦干。

You really kept your nose to the grindstone this year, and it paid off!
你今年真的很刻苦，把债都还清了！