Abstract: A developing unit for an electrophotographic processor includes a developing roller and a doctor blade for controlling an amount of developing material on an outer surface of the developing roller. A developer housing stores the developing material and has an opening for accommodating installation of the developing roller. First and second arm plates are connected to first and second ends of the developer housing, respectively. The first and second arm plates each have an eye into which the developing roller is inserted. First and second protrusions extend outwardly from the first and second arm plates, respectively, and provide surfaces upon which the doctor blade is placed during assembly of the developing unit to ensure a uniform spacial gap between the outer surface of the developing roller and an edge of the doctor blade.