Abstract: A cleaning process and apparatus for cleaning small diameter clogged holes or passages fashioned as deep through-holes or small diameter through-holes of varying sizes. The holes may be provided in dies for enabling a pressing of materials for manufacturing of pellets such as feed stuff pellets. The cleaning is effected by directing at least one water jet having a diameter less than one-half of a smallest diameter of the hole or passage to be cleaned. The cleaning medium is supplied possibly at supersonic speed. It is also possible to clean radially oriented holes or passages in the die by ejecting the cleaning medium from nozzles of the apparatus.