## 1 Introduction
Since high roughness corresponds to discontinuities in the wood tissue, it is expected and inevitable that this is also associated with the retention of a higher moisture content, the higher potential of wood biological damage, wood degradation by the action of microorganisms, a deterioration in wood substrate, etc. Therefore, the smoothness of wood surfaces has been associated with a longer service-life duration of wood and wood structures. Currently, empirical procedures and models have been applied, using several surface roughness indexes of \(Ra\), \(Rz\), \(Rq\), \(Rk\) and \(Rap\), among others [21]. However, the most commonly used surface roughness indexes being recorded, in order to define wood surface roughness, are as follows: \(Ra\), which corresponds to the average of the values of the roughness profile; \(Rz\), the mean value of the roughness depths of different sampling lengths; and \(Rq\), the largest roughness depth width. Determination methods can be applied either with or without contact with the wood surface. Contact methods employ a stylus tip, pneumatic methods, and tactile sensation [22]. A quite commonly used method is the use of a profilometer bearing a diamond stylus, which runs a path on the surface and records the surface roughness in different directions of wood grain [20; 22; 23]. The wood of chestnut is regarded as being classified among the most valuable timber species of Europe and presents a great range of uses and applications in the form of round timber, technical sawn wood, floors, furniture, high-value items, etc. [24; 25]. It is a ring-porous hardwood species with earlywood vessels that are of significantly higher diameter than those of latewood, presenting a clear ring arrangement [25]. Especially when sapwood is being transformed into heartwood, the earlywood vessels are usually full of tyloses, while latewood vessels are polygonal and are found in groups generating a flame-like design. This species' rays are more often uniseriate, rarely biseriate, and of different heights [8]. The parenchyma is mostly apotracheal and rarely paratracheal in places [8; 25; 26]. Chestnut wood is considered to be of medium density, approximately 0.57-0.63 g/cm\({}^{3}\), and in general, density is strongly related to ring width. Especially for ring-porous hardwoods such as chestnut, growth rings of high width tend to demonstrate higher values of density, due to the fact that earlywood remains more or less stable, while the increase in growth ring width is attributed to the increase in the latewood part. However, density is also slightly affected by the cambium age and appears to decrease as the tree ages [27; 28]. The outdoors exposure of wood, where intensive changes in environmental conditions take place, concerning relative moisture content, atmospheric precipitation, UV radiation, etc., causes chestnut wood to gradually deteriorate and discoloration of the surfaces occurs, regardless of whether the wood has been coated with mild hydrophobic solutions or not, which subsequently deteriorate the quality and roughness of wood surfaces [29]. According to the literature, only [PERSON] and [PERSON] [30] have dealt with surface quality of chestnut among other species. More specifically, they investigated how machining conditions (feed rate, spindle speed, step-over, axial depth, etc.) affected the roughness of chestnut, beech, and walnut specimens, concluding that the wood roughness was greatly influenced by the factors of cut depth, feed rate, and spindle speed. Therefore, a great lack of research measurements and data have been identified in the literature with regard to the surface roughness of chestnut wood and the factors influencing it, although chestnut constitutes such an important timber species, frequently used in applications where roughness is a crucial parameter.