Cutting forces in handheld wood sawing: a factorial study of tooth geometry and cutting direction

Abstract Controllable cutting performance is essential for handheld saws in both craft and professional wood processing. Despite the widespread use of side-bevelled handsaw teeth in manual and electrically powered tools, the combined influence of tooth geometry, set pattern, as well as cutting direction on cutting forces is not well understood. A Design of Experiments (DoE) approach was applied to evaluate the effects of tooth type (universal, UT; compound, GT), side-bevel, set, set pattern, and cutting direction on main ( F m ) and normal ( F n ) cutting forces. Experiments were conducted on Norway spruce blocks sourced from a single log, which was conditioned to achieve uniform moisture content and characterised using X-ray computed tomography. A custom-built cutting rig measured F m and F n under controlled cutting speed and depth conditions. A 2⁵⁻¹ fractional factorial design was applied as an exploratory DoE screening approach to capture main and two-factor interaction effects. F m was dominated by cutting direction and kerf-related factors, with GT teeth exhibiting lower F m than UT teeth in rip cutting. F n was primarily governed by tooth type, bevel, and set pattern. Interaction effects between geometry and cutting direction were statistically significant, highlighting the multivariate nature of the cutting process. Overall, cutting forces are governed by interactions between tooth geometry, set configuration, and cutting direction. The results provide a quantitative basis for further development of handsaw tooth design and cutting efficiency.