A semi-autogenous grinding mill, or slag mill, is responsible for grinding materials from large chunks into small, usable pieces for processing. The slag mill is usually part of the primary stage in the grinding process. Pieces of raw or fairly reduced materials are ground into smaller pieces for further processing or sorting. These machines are typically electrically powered, but have been modified from a variety of powering systems over the years.

A slag mill is most often used in the mining fields, particularly in the mining of precious metals such as gold, copper, silver, and nickel. The slag mill serves in the line of industrial mining equipment designed to process, crush, separate, or locate precious metals from mined coal. The slag mill is one of the large mining equipment pieces, and often requires mining equipment repair and maintenance. This is most often due to the large amount of heavy, residue bearing material being churned through the large drums of the grind mill. The slag mill uses lifting plates along the interior of the drum, which lift material throughout the rotations, causing them to fall onto one another to promote crushing.

It can often be necessary service a variety of industrial gold mining equipment, coal mining equipments, and other relevant large mining equipment. People who work on these machines must understand the intricate details involved with refurbishment of mining equipment and take great care in each stage of the machinery repair process. These details require a trained eye and skilled hand to ensure that the machinery continues to function properly.