Grinding grain size machines are called mills. In general, there are two basic methods of milling:
1- Shrinking the grain which the grain or other parts of it are converted into smaller pieces. 2. Sieving which is to separate and classify the various particles of resulting from shrinking wheat.
Hammer mills are made of fixed or swinging hammer mounted on the wheel axle and have a sieve. The speed of the hammer is between 2500 and 4000 rpm. The sieve is mounted on the bottom, up and away of the hammer to cross the grains.
In this way, the grains remain in the mill to be chipped enough to pass through the holes of the sieve. The hammer should not be contacted with the sieve, and the grinding of the material depends on the size of the sieve holes and the amount of material moving in Inside the mill. Hammer mill is especially suitable for grinding soft and medium materials. In some countries as Iran, to produce the flour used hummer mills. In this method, wheat is converted into flour and bran particles, and the separation of flour and bran is not feasible due to uniform particle size. Also, the seed particles are poured into the flour, and all the components of the wheat including shell, bud and endosperm are poured into the flour, and the quality of the flour produced by this method is not desirable for many products. The flour produced from the hammer mill is suitable for Sangak (Persian bread) bread.