Most of the large open gear sets for mining industry are designed according to AGMA 6014?A06 and AGMA 2001?D04. and rating according to AGMA standard (service factor) involve the final design of the pinion such as: material and heat treatment (through hardening or case carburized pinion)@ and the finishing process of the teeth (to achieve the design geometry). Basically@ customer specification and rating according to AGMA standard (service factor) involve the final design of the pinion such as: material and heat treatment (through hardening or case carburized pinion)@ and the finishing process of the teeth (to achieve the design geometry). Moreover@ the increase of applied load for a single meshing becomes a new challenge. In addition to the mechanical properties for the material used and its associated heat treatment requirements given in standards@ elastic and thermal behaviour and resulting accuracy@ as well@ have to be taken into account at design stage@ even for large open gears. Beside design consideration@ such increase of single meshing load cannot be achieved by using conventional manufacturing and quality control methods. Therefore@ improvements in manufacturing process and in quality inspections for such heavily loaded single large parts@ as already performed for smaller parts in batch are now mandatory to achieve these new design requirements. Based on examples@ in this paper@ it is presented such manufacturing and the associated quality controls improvements from steel fabrication to final machining for heavy parts@ to ensure the customer that the result meets the specification requirements.