A jigger machine is usually coupled with a classifier to form a grinding and classifying unit for operation. The mill grinds the material to be processed, while the classifier classifies the milled product into qualified and unqualified products.

The classifier classifies the milled product into qualified and unqualified products. The rejects are returned to the mill to improve the grinding process. The classifier operation and the grinding operation to which the classified return sand is fed form a grinding section. Classification can be preclassification, check classification, controlled classification or a combination of both. A grinding section using a rod mill in a two-stage milling process can also be used without a classification operation.

The main factors affecting the determination of the number of grinding segments are the grindability of the ore and the embedded characteristics of the minerals, the feed size of the mill, the required size of the grinding product, the production scale of the processing plant, and the need to deal with the ore and sludge separately. It has been proved in practice that with one or two grinding stages, the ore can be economically ground to any size required for beneficiation without the use of more grinding stages. The increase in the number of grinding stages to more than two is usually dictated by the requirements of the stage of beneficiation to be carried out.

The majority of metal ore beneficiation plants use a wet grinding process, and most of them use a ball milling process or a rod milling and ball milling process; in order to avoid over-crushing, a rod milling process is used for ores containing friable minerals, for example, tungsten, tin ore and some lead ores in a re-election plant.