Edge Runner Mill

The edge runner mill is also called a roller stone mill and is a mechanized form of mortar and pestle-type compression comminution. It crushes the materials into fine powders by rotating stones. The mill consists of two large rotating grinding wheels or stones turning slowly in a large bowl. In this mill, the material can be crushed or ground in a continuous operation.

Principle of edge runner mill

The edge runner mill mainly works on the attrition and impaction by which the crushing or grinding of the powder material takes place. The principle of size reduction by this mill are crushing due to heavy weight of the stones or metal and shearing force. Movement of stones or metal causes size reduction. The Edge-runner mill has the pastel equivalent mounted horizontally and rotating against a bed of powders.

Construction of edge runner mill

The basic parts of this mill consist of two heavy rollers and a bed made of stones or granite which is used for the grinding of the materials, Fig. 2.6. The rollers are mounted on the central horizontal shaft and move around the bed in a shallow circular pan.

Working of edge runner mill

The material to be milled is fed into the center of the pan and is worked outwards by the action of the wheels. Scrapers are employed in scraping the material constantly from the bottom of the wheel vessel after which it is fed to the wheel where it gets crushed to powders. The material is ground for a definite period and then it is passed through the sieves to get the powder of the required size. An electric motor in the basement provides power for the mill to start the device as used in flour mills. This mill is used for crushing or grinding various materials without the danger of clogging or jamming the machine by the accumulation of the ore with greater efficiency and in high comparative quantities. The crushed powder is discharged through the outlet at the bottom.

edge runner mill
Fig. 2.6: Edge Runner Mill (a) Schematic (b) Industrial Mill Used In Practice


  1. This mill is used for grinding most of the drugs to very fine powder.
  2. It is used to crush or grind all types of the drugs.
  3. It is most preferred for size reduction of non-sticky materials


  1. Very fine particle-sized materials can be obtained by this edge runner mill.
  2. It has a simple design.
  3. The major advantage of this mill is that it requires less attention during operation.
  4. The combinations of various elements in this machine makes it to operate with greater efficiency.
  5. Utilizes less power, and does not require frequent clean-up and particular adjustment.


  1. It requires more floor space than the other commonly used mills.
  2. It is not suitable for sticky materials.
  3. This mill produce lot of noise pollution.
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