Abstract: A mixer for liquids and liquid suspensions has a motor drive and housing which is portable and can be carried from tank to tank and attached to the tank where mixing is carried out. The housing depends from the yoke and contains a quill which is driven by the motor drive. A chuck mechanism is associated with the housing and quill to enable mixer impeller shafts to be held in assembled relationship in the mixer and readily removed and replaced with shafts having impellers specially adapted for the particular mixing application of interest. The chuck mechanism is operable even though the quill is hidden in the mixture housing.