Effects of Surface Roughness and Wood Grain on the Friction Coefficient of Wooden Materials for Wood–Wood Frictional Pair

In order to investigate the effects of the surface roughness and wood grain on the friction coefficient of wooden materials, the friction coefficients of solid wood, medium-density fiberboard (MDF), and particle board (PB) with varying surface roughness were tested by a friction coefficient tester. The friction coefficients of solid wood for a wood–wood frictional pair were measured under varying wood grain (the orientation of fibrils). The results showed that the friction coefficients of the solid wood increased linearly with the arithmetic mean deviation of the surface profile (Ra). The friction coefficients of MDF and PB increased sharply at first and then stabilized with increasing Ra. The friction coefficient of solid wood was respectively maximized and minimized when the grain directions of two wood specimens were both perpendicular to the sliding direction and perpendicular to each other.