Magnetic abrasive finishing (MAF) process is the method, which the permanent magnet field or electromagnet field is used to control the abrasive particles. The abrasive particles are supplied between the North-pole and South-pole of magnets and they can finish the surface of workpiece when the workpiece rotated.

Tungsten carbide bar is the high hardness material and the compressive strength is much higher than other steel, because the mechanical properties are so great so it has been widely used in cutting tools. The smooth surface of tungsten carbide is required in cutting tools, so magnetic abrasive finishing process was applied for achieving the smooth surface roughness.

In the paper, tungsten carbide was used as the workpiece, with 0.5mm diameter and 50mm of length. When magnetic abrasive finishing (MAF) process applied to finish the surface of material, the surface roughness, roundness, removal weight and changes of diameter were measured every 20seconds in the total time 160seconds. The best experimental conditions in this paper were found by using three methods for finishing. First, the changing of the workpiece rotational speed, secondly, the changing of the grain sizes of diamond abrasives, and thirdly, by using magnets in different shapes. First, the different of rotational speeds such as 1,000rpm, 3,000rpm, 10,000rpm, and 15,000 rpm were applied to process in 120seconds. According to the best result, it is shown that the best value of Ry was 0.03㎛ and the value of Ra was 0.02㎛, these results were obtained when the workpiece rotated at 10,000rpm in 120seconds. The total removal weight of the workpiece by abrasive was 0.00063g, which was better than other rotational speeds, and in the case of 10,000rpm, the best value roundness was obtained up to (0.12㎛). Secondly, when different sizes of diamond abrasives such as, 0.1㎛, 1㎛, 6㎛, 15㎛ were used, respectively. As the result indicates the best value of surface roughness and roundness were obtained when finishing with 1㎛ grain size of diamond paste. Thirdly, there are three types of magnet shapes were used in this research such as the end pointed A-type of magnet, 2.5mm tip flat B-type of magnet and the end shape which is an R-shaped C-type of magnet. The result shows that when the end pointed A-type of magnet was used the best value of surface roughness was obtained. The best result was obtained because the shape of magnet was the pointed style so the force of magnet can control the particles of unbonded magnetic abrasive well.

According results, it is shown that for achieving the smooth surface roughness of tungsten carbide, the surface of workpiece can improve with 1㎛ grain size of diamond abrasive and end pointed A-type of magnet at 10,000rpm.