磨 has two pronunciations: mó (to grind, polish, dawdle) and mò (millstone, to grind grain: 磨豆腐 = grind tofu). The mó reading is much more common.
culture
铁杵磨成针 (tiě chǔ mó chéng zhēn) — 'grind an iron pestle into a needle.' A famous idiom about perseverance, attributed to a story about the young Li Bai (李白).
