オーガビットによる木材の機械穴あけ加工における切削力 : ビットの持ち上げ力と安全作業について

Machine boring of agathis (Agathis alba Foxw.) and other five wood species with both augar bits with a feed-screw at the center and screw-killed bits by use of drilling machine were performed under boring conditions of 1500 rpm of spindle speed and 0.1-0.3 mm/rev of feed per revolution, cutting force (thrust and torque) was measured. Maximum lifting forces of wood by augar bits with different diameters at the first stage of boring were examined and were compared with those for the screw-killed bits. Furthermore, the difference of mean cutting force for 15-mm boring depth of outer corner of bit between the two kinds of bits were also examined. From the experimental results, it became clear that the maximum lifting force of wood by augar bit increased with increases in bit diameter or feed per revolution for all wood species. Thus, since machine boring of wood with augar bit with holding it by hand can be regarded to be very dangerous, safty working of wood machine-boring for pupils at juniar high school was discussed.