Studies on Quantification of Sensuous Sharpness and Mechanical Sharpness of Wood Cutting Tools. III. Effects of the Microbevel Angle of a Knife and the Horizontal Mouth Opening between a Chip Guide and a Knife Edge on the Prevention of Occurrence of Torn and Chipped Grain in Wood Cutting against the Grain

摘要

In the wood cutting process with a knife equipped with a chip guide, it is important to obtain the optimum conditions of the microbevel angle of the knife (β1), the length of the rake face of the knife with the microbevel (ℓR),and the horizontal mouth opening (h) and to investigate the changes of cutting force acting on the knife and on the chip guide with β1, ℓR, h, and the grain angle (φ1(Figs, 1～3, and Table 1). In order to obtain quantitative information on them, the basic orthogonal cutting tests, in which the materials used were air-dried wood boards of western hemlock (Tsuga heterophylla SARG.), were performed using the knife as shown in Fig .3 (Figs. 4 and 5, and Table 2). The main results obtained are summarized as follows : The roughness of machined surface is affected by β1, ℓR, and h, as illustrated in Figs. 7 (a) and (b), 9 (a)and (b), and 11 (a) and (b). On the basis of these results, the other results on the cutting phenomena, and the results on the cutting- force components (Figs. 6, 8, and 10), the optimum cutting condition is β1≒ 55.0°, ℓR ≒ 0.35～0.40 mm, and h ≒ 0.60～1.20 mm, under cutting angle of the knife (θ) of 35° and depth of cut (t) at 0.3mm.