- Jet mills are common devices used in industry for the fine milling of dry particulate materials. The size reduction is caused by repeated impaction events between particles. Although many parameters affect the performance of a jet-mill, only a few of them have been investigated by researchers to date. Furthermore, the published investigations test only a few materials. In order to bridge the knowledge gaps which exist, a new experimental apparatus was designed and constructed to enable experiments involving as many influencing parameters as possible. The new apparatus enables changing of the material feeding, mass flow rate, air flow rate, nozzle parameters (velocity, diameter, angle, number and shape), grinding chamber height and the classifier orientation. In this paper, preliminary experimental results concerning a number of the aforementioned parameters and their effect on the mill performance are presented.