Cost efficient, high value for money timber is essential for the welfare of our Nordic citizens and for the profitability of our forests and the forest industry. The sawmill recovery rate, or yield, is one of many influential factors. In the primary breakdown, ca. 10% of valuable round wood is converted into low value sawdust by the saw kerfs. This has remained so despite a never-ending technological development – which has mainly resulted in higher production capacity and lower need for operators. The size for new sawmills, the annual capacity, increased proportionally. However, restricted by limited roundwood supply, the last two decades there was no room for new sawmills in Norway. The largest Norwegian factories have been reduced to SME sawmills producing one third of a new mill.
Most kerfs are ca. 4 mm wide: frame saws, circular saws, double arbor circular, pre- sawing circular elements in chippers and profiling heads. Band saws might be thinner, at the trade-off of accuracy. Exactly the same kerf thickness was in use 250 years ago. With modern steel, blade failure is less frequent, and alloys like stellitt reduces the need of re- sharpening, even at high feed rates: the result was always higher capacity. Even the ability of sawing parallel to the pith, curve sawing, has been reduced.
The technical options and profitability effects for a medium-sized sawmill to convert to saws with thinner kerfs and improved curve sawing properties are discussed. Some techniques are readily at hand – for the sawmill prepared to ask.
Keywords: Sawmill recovery rate, Thin kerf sawing, Improved curve sawing
Authors
Peder Gjerdrum
Norwegian Forest and Landscape Institute
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