Friction mechanisms in wood cutting

The variation of the coefficient of friction with normal load and tool surface finish in slow speed orthogonal cutting of white fir was investigated to determine the relative importance of different sources of friction. Cutting forces were measured as a function of tool-chip contact length and tool surface roughness. The coefficient of friction was independent of tool roughness for roughness in the range of typically well-finished cutting tools but did become a factor for large values of tool surface roughness. The data indicate that for well-finished cutting tools the primary friction mechanism is adhesion between the tool and work and that for rough tool surfaces the effect of tool surface asperities (unevennesses) as they advance through the chip becomes an important source of friction.