This study covers the use of a modified button pressing machine as an axial-loaded shear test apparatus for shear strength measurements of mineral filter cakes. Mechanical properties of very fine grained mineral filter cakes are directly measured by uni-axial tests applying an external load among the diameter of the cakes via a moving crosshead. A uni-axial button pressing machine used in textile industry was so modified that it is possible to measure the shear strength of dolomite and calcite pressure filter cakes with satisfying results. The results obtained with this machine are also in good agreement with the other apparatus used in previous studies, like Fischer Test Apparatus and Universal Sand Strength Machine.