Comparison results of visual and machine strength grading of Scots pine sawn timber from the Greater Poland-Pomerania Forestry Region in Poland

Comparison results of visual and machine strength grading of Scots pine sawn timber from the Greater Poland-Pomerania Forestry Region in Poland. The paper presents an analysis of the strength grading results performed by two methods – visual (appearance) and machine, carried out for sawn timber obtained from the Greater Poland-Pomerania Forestry Region in Poland. Visual strength grading was performed in accordance with PN-D-94021:2013, while the machine strength grading with the use of MTG device (Brookhuis Electronics BV). As a result of the tests, it was confirmed that a large part of timber batch (39%) was classified as a reject while visual grading, when the machine grading resulted in a very small share of sawn timber classified as rejects (only one piece). At the same time, during machine strength grading there was only one sawn timber piece that was not classified for any class or a reject. Based on its visual appearance, this timber element should be graded as reject.