Operational performance of individual handsaw teeth

摘要

Initially a study was conducted using a single ripsaw tooth to cut a variety of woods both along and across the grain. A CNC router machine was used to control the tool path and apply cutting depths of between 0.4-1.2 mm. A series of mechanical tests were conducted concurrently, evaluating the same wood varieties in bending (across the grain) and shear (along the grain). A second study evaluated two different tooth geometries: a bevelled handsaw tooth and an unbevelled handsaw tooth. In this instance only one wood variety was machined (Douglas fir) both along and across the grain. To ensure a lower cutting depth (≈0. 15 mm) a shaper machine was used to control the tool path. A high speed camera with macroscopic lens was used to capture the chip formation in real time. For the first study, a triaxial dynamometer was used to record the forces acting on the ripsaw tooth. Modulus of rupture (Pa) and bending toughness (J/m3) were found to have the greatest influence on cutting forces across the grain. Likewise, shear strength (Pa) and shear toughness (J/m3) were found to have the greatest influence on cutting forces along the grain. From the second study, the high speed footage of the unbevelled handsaw tooth showed this to be the most effective at removing material along the grain in a “chisel like” cutting action. The high speed footage of the bevelled handsaw tooth showed that the sharp lateral edges of these teeth are ideal for severing the wood fibres across the grain in a “knife like” cutting action.