Deviations of kerf by handsaws III: the bend of saw blade by unsymmetrical set

To clarify the inducing mechanism of kerf deviation caused by unsymmetrical set of the handsaw, we hypothesized that the moment on the bottom edge of the saw blade, which is generated by the unsymmetrical set on handsaw teeth, bends the saw blade and this deformation should be one factor of the kerf deviation. To verify this hypothesis, the bend of a saw blade was examined by experiment and by calculation. In the experiments, a model tooth was attached to an actual handsaw. In the calculations, a saw model with a rectangular prism as the model tooth was analyzed by the finite element method. Loads were applied on the model tooth or the rectangular prism. From both the experiments and the calculations, the following results were obtained: (1) the deformation of the handsaw was caused by the unsymmetrical set in the length direction and the height direction of the saw blade; (2) the deformation and the inclination of the blade was larger at the front part of the saw than at the butt part; and (3) comparing the saw handle fixing conditions, the kerf deviation in the sawing line was supposed to be larger in the free handle condition and that kerf deviation in the depth direction was larger in the fixed handle condition. Based on the above results, it is apparent that one of the kerf deviation mechanisms originated from unsymmetrical set on the saw teeth. Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, Japan, August 2004.