In the veneer cutting process, compression and restraint caused by the pressure bar play an important role, but few studies have dealt with their effects on the frictional coefficient on the tool rake-face. Therefore, the main purpose of the study reported here was to obtain a quantitative information on these aspects. In this study, the rollr bars with various diameters (D) and of various rolling types were prepared to vary depth (r(t)) of restraint by interface between face of the roller bar and the tool rake-face, action area of restraint, and degree of adhesion between face of the roller bar and tight side of veneer. Before cutting, test specimens were preheated in water at about 95-degrees-C for 4 hours. White seraya (Parashorea sp.) veneer, 10 mm thick, was cut with five rolling types of the roller bars, and frictional (F) and normal (N) forces acting on the tool were measured. Based on these measurements, the frictional coefficient (mu) on the rake face was calculated from Eqs. (17)-(19) and its variation under various experimental conditions was determined. The main results obtained are summarized as follows: (1) The values of F and N increase with increase not only of r(t) but also of D (Fig. 4). (2) The value of mu decreases with increase of r(t) in the range of 0 < r(t) less-than-or-equal-to 1.0 mm, but increases remarkably with increase of r(t) in the range of r(t) > 1.0 mm. These decreasing and increasing tendencies with r(t) vary under various combinations of rolling types and diameters (D) of the roller bars (Figs. 5 and 6). (3) The value of mu is smallest when cut with a RR-type roller bar (Fig. 5). (4) The value of mu decreases with increase of D, but the decreasing tendency of mu varies with r(t) and rolling types of roller bars (Fig. 7).
