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Abstract
Cutting resistance when sawing with narrow kerf saws can be influenced by the moisture content and temperature of the wood and the feed speed. In this study, experiments were conducted using a sash gang saw in order to investigate the frozen wood cutting process. A set of experimental samples of Scots pine were frozen in a climatic chamber before testing. Cuttings were performed on the frozen and room-temperature wood pieces. Cutting power during sawing was determined as well as the obtained surface roughness and thickness variation. Values obtained from this study of the specific cutting resistance when using narrow kerf saws were greater than the reference data found in the literature. A decrease in the dimensional accuracy of sawn lamella was observed for frozen wood. On the contrary, sawn surfaces were smoother compared to the non-frozen wood samples.
Processing frozen wood during winter is an old challenge for craftsman and sawmillers. Some of the knowledge related to the physics of cutting frozen wood, as found in the literature, is summarized below.
Lunstrum (2001) and Jeronimidis (2005) reported that frozen wood is more brittle than unfrozen wood and, therefore, can be cut cleaner. The superior cutting performance is an effect of the improvement in the mechanical properties of the frozen wood (Kuricyn 1981), especially hardness and dynamic failure stresses (Jeronimidis 2005). Moreover, because the friction coefficient between wood and steel is significantly lower when sawing frozen wood, it is possible to use saws with smaller clearances per side (Kuricyn 1981). It has also been reported that fuzzy grain generation has been lessened. The heating of the sawblade is reduced as a consequence of low sawblade friction and the low initial temperature of the wood, which naturally cools the sawblade. It was also suggested that cutting edges with built-in chip breakers should be used because they could help pulverize the dust into smaller particles. This would aid in the dust escaping since chips and sawdust cut from frozen wood have a tendency to conglomerate and remain in the gullet. Another recommendation for sawmillers processing frozen logs during the winter season was to reduce the circular saw's rim speed (cutting speed) to about 30 percent (Lunstrum 2001).
Other problems related to cutting frozen wood are associ-...