Characteristics of Torques for Driving Screws into Wood-Based Composites

Critical torque factors, typically used for screw-driving behavior, were used to investigate characteristics of torque behavior in wood-based composites. Factors investigated were wood-based composite type, embedded screw orientation, and pilot-hole diameter. Recorded torque-time curves, which illustrated the complete process of driving screws into wood-based composites, indicated that screw torques behaved differently in sides and faces of wood-based composites and that the whole screw-driving process can be divided into two phases. Critical torques of these two phases on torque-time curves were defined and named. Statistical analyses of evaluated factors on critical torques, such as maximum drive torques (MDT) and stripping torques (STT), indicated that those factors had significant interactive effects on critical torques. Oriented strandboard materials evaluated had mean MDT from 1.04 to 1.75 Nm, mean STT from 3.30 to 5.91 Nm, and mean STT-to-MDT ratios from 3.18 to 3.53. Particleboard materials had mean MDT ranging from 1.01 to 1.84 Nm, mean STT ranging from 3.12 to 6.05 Nm, and mean STT-to-MDT ratios ranging from 3.08 to 3.29