Effect of Grain Direction on Drilling Resistance Measurements in Wood

Abstract

ABSTRACT An IML-Resi PD-400 drilling tool with two types of spade drill bits (IML System GmbH, Wiesloch, Germany) was used to study the influence of the drilling direction in relation to wood grain orientation on drilling resistance (DR) and feeding resistance (FR) measurements. The drilling tests were performed on Scots pine, European beech, English oak and Silver poplar conditioned in a standard climate. The differences in DR between radial and tangential drilling direction were negligibly small or minor for both drill bit types. In contrast, the difference between longitudinal and tangential drilling direction was more pronounced but differed between wood species and drill bit types. FR was the most sensitive parameter to changes in the wood grain orientation when using a drill bit with a single major cutting edge. The mean FR decreased by approximately 27% for Scots pine, 33% for Beech, 37% for Oak and 40% for Poplar when changing the drilling direction from longitudinal to tangential. It was concluded that the drilling direction between longitudinal and transversal drillings needs to be considered for the prediction of wood properties based on DR measurements. Potential applications of drill bits with a single major cutting edge can be the object of further studies.