PEER-REVIEWED ARTICLE bioresources.com Author et al. (2015). “Roughness of pine wood,” BioResources 10(3), 5554-5562. 5554 Effects of Machining Methods on the Surface Roughness Values of Pinus nigra Arnold Wood Murat Kılıç In this study, samples were subjected to the following surface treatment techniques: sawing with a circular saw, planing with a thickness machine, and sanding with a sanding machine (with No. 80 sandpaper). After samples were treated radially and tangentially with machines, their surface roughness values (Ra, Ry, and Rz) were measured according to ISO 4288. When statistics related to surface roughness values (for Ra, Ry, and Rz) were analyzed, it was found that surfaces processed with the thickness machine exhibited the smoothest surfaces. Also, according to the same statistical tables, the lowest surface roughness values were found for surfaces cut tangentially. Keywords: Surface roughness; Pinus nigra Arnold wood; Wood machining; Cutting directions Contact information: Kırıkkale University, Faculty of Fine Arts, Deparment of Interior Architechure & Environment Design, Yahsihan, Kırıkkale, Turkey; *Corresponding author: muratkilic@kku.edu.tr INTRODUCTION The success of surface treatments in protecting wood as a final product and in increasing its visual appeal depends on the smoothness of its surface material (Richter et al. 1995). Also, the surface roughness of woody material significantly affects the general performance of the product in terms of the joining of wood with adhesive (Burdurlu et al. 2005). One of the most important criteria in the determination of a material’s surface smoothness is surface roughness. There are several factors influencing the surface roughness values of wood; these can be simply regarded as the annual ring variation, the density, the cell structure, and the latewood/earlywood ratio. The surface quality of the final product and accordingly its cost are also influenced by the machining used in manufacturing, the characteristics of the raw material, and/or the combination of these two parameters (Kilic et al. 2006). Increased cutting speed, or rpm, generally results in the improved surface quality of wood products (McKenzie 1960; Lemaster and Beall 1993; Mitchell and Lemaster 2002; Kilic et al. 2006). The planed surface characteristic of solid wood is a function of its machining quality, which is directly related to knife marks per cm and not cutterhead speed alone (Davis 1962; Akbulut et al. 2000; Burdurlu et al. 2006). Sand marks were also found to be important parameters influencing the quality of the surface. Grit size, and relatedly an alteration from the expected surface quality degree, would also result in a cost increase and wastage of raw material. Surface irregularities on solid wood are not always distinguished entirely compared to the other materials. Surface roughness of wood, at present, is defined using technical terms, given a representative or numerical reading of the surface topography. However, no universally accepted standard for the method has been established for these purposes, even though several methods are available such as stylus, optical profilometer, image analyses techniques-using a video