Effect of thermal rectification on machinability of Eucalyptus grandis and Pinus caribaea var. hondurensis woods

Thermally rectified wood acquires colors similar to those observed in tropical woods, improved resistance to fungi and weathering, higher dimensional stability and lower hygroscopicity. Little information is available on the effect of heat treatments on the machining properties of wood. In this work, relatively low-valued woods (Eucalyptus grandis and Pinus caribaea var. hondurensis) underwent a variety of thermal rectification treatments (from 140°C to 200°C), performed in presence or scarcity of oxygen. Heat-treated wood underwent peripheral knife-planing (15°, 20°, and 25° rake angles) and sanding tests (60–80, 80–100, and 100–120 grit). Surface quality was evaluated as a function of the incidence of machining defects and uniformity of texture (planed surfaces), and roughness and wettability (sanded surfaces). Thermally rectified samples provided better surface quality after planing, and increased surface roughness after sanding, compared to control samples. The increment of treatment temperature caused an increase in wetting time, which indicates reduced hygroscopicity.