Systematic classification of commonly used timber species for finger-joint mixed panels in Sri Lanka

Off-cut wood pieces are often dumped or used as fuel wood. A certain portion of timber has to be removed also due to inadequate length of sawn timber material. Finger joint, a method which connects two small pieces of timber is identified as a sound technique to minimize timber wastage. At the finger joint production process, different timber species are bonded together for making finger-jointed mixed panels. In this connection, the selection of the best possible combination of timber species is vital as the success largely depends on the mechanical and physical properties of the pieces. Workability, on the other hand, is another key factor which minimizes manufacturing defects. However, expansion of the finger joint industry is restricted due to the unavailability of a reliable timber classification system based on wood properties. Therefore, the present study focused on developing a classification system for selected 32 clear timber species based on physical, mechanical and anatomical properties of wood. Factor analysis was used in preparing the Total Wood Index (TWI) and timbers were grouped into four categories as low, medium, high and very high based on TWI. It is recommended for selecting suitable timber species from the TWI-based groups to ensure the best matching thereby the attractive aesthetic appearance in finger-joint manufacturing can be achieved.