Grinding target definition: the limiting particle size for a grinding operation corresponds to which particle in the feed/sample?

Introduction / Context:
Comminution objectives are often specified as “all material below X μm”. Achieving that specification requires consideration of the coarsest particles present.

Concept / Approach:
The limiting size to which the entire sample must be ground is governed by the largest particle; you must supply enough energy and residence time for these coarsest pieces to reach the target size. Finer particles are already below specification and need no further breakage.

Final Answer:
Largest particle