grist for the mill

• grist to the mill (UK), grist to one's mill

grist for the mill (uncountable)

1. (idiomatic) Something that is useful or that creates a favorable opportunity.
   • 1979 August 4, Lisa Nussbaum, “Lesbianism 101”, in Gay Community News, page 15:

     The Lesbian Primer does not profess to cover every conceivable aspect of lesbianism. But for someone trying to get or expand knowledge of the subject, this book provides much good grist for the mill.

   • 2003, Peter Lefcourt, The deal: a novel of Hollywood:

     They were sitting across from each other at the bar as Lionel described his odyssey across the country in a Trailways bus, gathering material, as he put it. It was all grist for the mill, life real and raw out there west of New Jersey.

   • 2005 March 2, Leslie Feinberg, “Even McCarthy was gay baited”, in Workers World‎:

     In 1951, Guy Burgess and Donald Maclean, two gay double-agents working in British intelligence, fled to the Soviet Union. This was grist for the mill, linking homosexuality with communist "treason."

• Often found in the expression it's all grist for the mill and variations thereof.

• food for thought
• more sacks to the mill