The main purpose of this test was to find the difference in the sawing efficiency between the green woods (BUNA) and frozen woods; the former were stored in a yard about 150 days after cutting, the latter were frozen in winter at Hida district (Temperature is shown in Fig. 4).
The tests were carried in a usual practice of sawing by a 42" bandsaw machine (20 H.P.), eguipped with automatic feed carriage (3 H.P.) using the perfprated saw blade which is 24 B.W.G. thick, 4" wide, and of whrch diameter of hole is 12.7-25.4mm, and distance of hole centers is 33.5-532.0 mm, and rate of hole area (Total area of holes/Total area of band saw blade) ε is 0.5-4.0%. The model of saw blades are shown in Fig. 1, 5, 8. (The model of the original no-hole blade is omitted).
Cutting speed V (m/s) were varied in 6 kinds of speed in a range of 33.5-50.3 m/s and saw cuts were made as fast possible within a limit of good cutting.
Assuming that the cutting force F_<max> (kg) could be estimated by the net electric power K (KW) reguired for cutting, F was calculated by the next formula,
F = (102 K) / V
The relationship among the cutting force F (kg), the depth d (mm) of wood cut per tooth and the side friction b (kg) of saw blade is the following,
F = αd + b (Here α is a coefficient.)
Reltions between V (m/s) and K (KW) are shown in Fig. 2 (green woods) and Fig. 6 (frozen woods), and relations between F (kg) and d (mm) in Fig. 3 (green woods) and Fig. 7 (frozen woods).
These results seem to show that it takes larger electric load K (KW) in a cutting of frozen woods like BUNA (Fagus crenata Blune) by a perforated bandsaw than that of green woods. Generally speaking, the cutting force F (kg) and the coefficient α seem greater by the perforated bandsaws than by the non-perforated ones and we find these trends are remarkable noticeable with frozen woods.
We surppose that the greater electric lord K (KW) and the greater coefficient α should be originated in the frozen condition of woods and in the extrusive resistance of sawdust adhered to the face of cutting (as shown in Fig. 12), because the frozen sawdusts decrease in proportion to the rate of hole area ε% as shown in Fig.11.