Abstract
Japanese cedar, sugi (Cryptomeria japonica D. Don), which is a main conifer species in Japan, has earlywood of low density. A large difference in hardness is observed between earlywood and latewood in sugi. Cutting and many other machining processes are quite troublesome issues with this wood, and result in inferior surfaces. Therefore, sugi samples were subjected to lateral thermal compression loads to achieve a hardness of earlywood approaching that of latewood. After machining by orthogonal cutting, the cross sections of the resulting chips were observed at the cellular level. The results obtained are as follows : 1)Most of the cell walls in the earlywood were deformed by thermal compressed treatment of 50% compliance, and its durometer hardness became close to the value (HDD 60) of the latewood. 2)The cross section of cells in the chip surface by orthogonal cutting appeared U-shaped in the case of the sugi wood compressed to 50% compliance and a good machined surface could be confirmed. In particular its effect was remarkable in the ray neighborhood and around the annual ring boundary. 3)It is concluded that as one of the planes which solve a problem of the surface roughness in the machining of sugi wood, the thermal-compressed treatment is useful.
