Screw thread shape and fastener type effects on load capacities of screw-based particleboard joints in case construction

In this study, the suitability of several mostly screw-based fasteners for connecting 5/8-inch- (15.87-mm-) thick furniture grade particleboard was assessed. Separate statistical tests were made for the effects of screw shank diameter, screw thread pitch, screw thread design, and fastener type (screw, screw PVC anchor, or dowel) on edge screw withdrawal resistance (SWR), bending moment resistance of corner joints, and lateral edge load of butt-jointed shelf units. A thicker shank diameter (0.252 in) gave significantly improved edge SWR and bending moment resistance but thinner screws gave the highest edge load of shelf joints. A thread pitch of 9 threads per inch (tpi) gave the highest edge SWR, and screws with a fully threaded shank performed best in the lateral edge load tests. Beveled threads made little difference to performance compared with the same screw brand and type with plain threads. Opposing trends for edgeSWRand lateral edge load of shelves with increasing screw shank diameter are interpreted in terms of fracture mechanics and contrasting load distribution patterns on the substrate surrounding the fastener. Combining screws with a large expandable PVC anchor or replacing with an unglued dowel connector reduced the fastener performance in all three tests.

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