Fig. 1
From: Wood machining with a focus on French research in the last 50 years
Evidence of a narrow shearing zone for continuous chip formation (from Thibaut 1988). Top machining of polymer (PMMA), bottom wood machining (Plane wood). ϕ is the angle between shearing plane and cutting direction (shearing angle) measured on the picture, ϕt is the theoretical shearing angle calculated from Merchant’s theory using friction angle β coming from experiment (Thibaut 1988), α is the tool rake angle, β is the friction angle between tool and material