### A Magnetite Ore In Eastern Hebei China

2.4. bond ball work index test a grinding mill (f305 mm 305 mm) was used for the bond ball mill work index test [18–21]. this ball mill was ﬁlled with 285 steel balls (total weight of 20.125 kg) at an operation speed of 70 rpm. the feed sample was prepared via crushing and sieving, giving rise to a size smaller than 3.35.21 conclusions continued in the present work, equations were also derived, giving: zthe ball-mill power drawp as a function of its dimensions: internal mill diameter d and length l, zthe ball-mill power drawp as a function of the feed d f (mm) and the product size d (mm), the bond work index w i (kwh/short ton) and the mill throughput t (short ton/h), zthe ball-mill dimensions (d and l), when.