Effect of Sanding Factors on Surface Roughness of African Rosewood (Dalbergia melanoxylon)

Dalbergia melanoxylon (African Blackwood/Mpingo) is a tree species known for its high density and hard structure and is widely used in producing musical instruments, luxury furniture, and handicrafts. The surface roughness of wood is determined by certain sanding factors. This study investigated the factors affecting the surface roughness of Dalbergia melanoxylon wood and determined optimal sanding conditions. Surface roughness was evaluated using Ra (average roughness), Rq (root mean square roughness), and Rz (maximum profile height) parameters, and differences between groups were statistically examined using analysis of variance. The results showed that the most influential factor for Ra and Rq was the sandpaper grit size, with contributions of 53.29% and 36.39%, respectively, while for Rz, the measurement direction was the most influential factor, with a contribution of 43.20%. The highest roughness values were obtained with 80 grit sandpaper, 15 s of sanding time, and measurements taken perpendicular to the grain, with Ra = 4.071, Rq = 5.668, and Rz = 35.207 µm. On the other hand, the lowest roughness values were obtained with 220 grit sandpaper, 60 s of sanding time, and measurements taken parallel to the grain, with Ra = 2.116 µm, Rq = 3.160 µm, and Rz = 22.668 µm. According to the Duncan test results, the combination with the lowest surface roughness was 220 grit sandpaper, 60 s of sanding time, and measurements taken parallel to the grain. In conclusion, for dense and hard-grained woods such as Dalbergia melanoxylon, fine sandpaper and longer sanding times are the most suitable conditions for optimizing surface quality. These findings provide an important reference for quality control processes and industrial applications of wooden decorative surfaces.