Abstract: The system for measuring wear in a grinding mill has at least one bolt passing through the shell and a wear plate. The bolt has an elongated oblong-shaped bolt head extending through the wear plate, flush with a surface of the wear plate. The bolt head is exposed to a same abrasion as the wear plate. The bolt has a groove there along and a plurality of wire loops embedded in that groove. Each wire loop extends to a distinct point along the bolt head, such as to form a ruler along the bolt head. A mobile transmitter-receiver is mounted to the stem of the bolt and is connected to the wire loops. The mobile transmitter-receiver has electronic circuitry therein for detecting broken loop conditions and for transmitting these conditions to a remote receiver where the conditions are related to degrees of wear on the wear plate.