Complex sentence: Devices of this sort are cheaper than burr grinders, but the grind is not uniform and will produce particles of widely varying sizes, while ideally all particles should have the same size, appropriate for the method of brewing.
Split into simpler sentences: Devices of this sort are cheaper than burr grinders, but the grind is not uniform and will produce particles of widely varying sizes. Ideally all particles should have the same size, appropriate for the method of brewing.