Flour and other mills are lucky, coffee mills, bad omen.
Dream dictionary: Mills dream meanings
Riches and success in proportion to the quickness of their movements. To work a flour mill means wealth through industry. To turn on a coffee mill means vexation and sorrow. To turn on a spice mill shows an uncertain and prolonged enterprise or melancholy.
(Mill) A sugar mill in a dream represents success in the world, sufferings, burial, money, usury, the release of prisoners, a bathhouse, a lavatory, discarding what is shameful, waters, spinning, breathing, a college, or a fellowship house. In general, all types of mills represent good news and guidance. (Also see Oil Press)