There has been a diligent effort in utilizing human beings as manpower in various types of industry in the present era as minimum as possible, for otherwise, it would need many requisites such as a technical knowledge and skills, an overture to extra expenditure, and without a doubt, would be extremely much time consuming, not to mention the great range risk of human errors. In order to discontinue using manual polishing, this research offers analysis of polishing of a conical shaped steel material (SPK) forging gear die, produced by EDM process using abrasive flow machining technique. As of now this die is being manually finished, which is very costly, and time consuming. The identified conical rotating gear, is used as a free wheel in the differential of vehicle. Abrasive flow machining is usually used for polishing of partial areas of the workpiece, which would take place in an abrasive flow direction. Since the geometry form of the gear die has not have any such characteristic, therefore an intermediate piece called "Mandrel", has been used to create a passage for the distribution of the flow in the curved die. Two different mandrel design for simulation purposes have been used. In the first design, a series of perforated holes have been used, for the fluid to enter into the die. In the second design, all the perforated holes are replaced by three grooves, so that the fluid flow would travel in and out more freely. In both designs, in order to create gaps for the fluid passage going through the geometry of the die, a smaller scale gear geometry has been used, with three scales of %2, %4, and %6 smaller than the die's geometry has been considered. Simulation of flow in the first half cycle showed that the pressure distribution in all cases are equal. Comparing simulation processes, the flow of both the back and forth cycle specified that the pressure in any direction point is consistent of a fixed amount equal the two half cycle in total. This represents a uniformed polishing in the die. Considering the results of simulations, the first mandrel design with 3 millimeter gap, was chosen because of the simplicity of manufacturing. The experiments were based on mixed Taguchi method ( ), which showed an almost uniformed polish of the die. It was specified in the experiment, that the bigger the size of the abrasive sands is the more chances for material removal rate increase would be. Also in most cases, in high concentration of abrasive, the level of removal, has decreased, for the cause of extra rush of compressed particles. The analysis of variance proved that the parameter of the abrasive grain size is the most effective factor. With the Regression analysis, an equation has been developed to forecast the surface roughness by maximum of %8.5 error. Keywords: Finishing, Abrasive Flow Machining, Mandrel, Conical Gear Forging Die, Simulation.