Curve sawing effects on board dimensions when rip-sawing with a circular saw blade

Curve sawing means advantages for yield and quality of sawn boards. However, for circular saw machinery deviations of saw kerfs give losses of valuable board volume. Deviations give thinner boards but also slight cupping of the cross sections. Theoretical calculations show that even with moderate (large) curve radii, these saw kerf deviations are typically 0.2-0.6mm for normal circular saw machinery and Swedish log material. The test sawing reported here was made in order to give experimental values that can be compared to theoretical values. Fifty normal logs and 50 curved with top diameter 236-248mm were cut with sawing pattern 3X with center boards 51x149mm. The average curve radius of the curved cants that were cut in the resaw was 132m (bow height 19mm) and the theoretical saw kerf deviation for this radius is 0.31mm. The experimental results show that the thickness reduction at the measuring points for curve sawn boards compared to straight sawn boards was in average 0.19mm to be compared with the theoretical value of 0.20mm. Cupping was more difficult to measure but results seem to agree well between theory and experiments.