Testing the strength of beech (Fagus sylvatica L.) and pine corner joints (Pinus sylvestris L.)

The work encompassed the strength testing of corner L-joints on chairframes made of beech and pine. The aim was to compare the results from previous work on similar joints with modern joint elements in order to assess their practical applicability. The task was to evaluate the physical and mechanical characteristics that determine the strength of L-joints in construction of the solid wood furniture. The experiment was performed on two groups of specimens. One of them consisted of Minifix harpoon bolts in plastic dowel, which are fixed by cylindrical wedge. The other type was a joint with Minifix threaded bolts in metal socket which are fixed with cylindrical wedge. The joints have been tested to the point of breakage in a static loading-testing machine. The results show that the joints with Minifix harpoon and Minifix fastenings exhibit smaller strength in comparison with the glued wood joints of the same shape and dimensions. The physical and mechanical parameters that were shown to influence the strength properties of joints were the exactness of dimensions of joining parts and the rotation angle of the wedge. In conclusion it can be stated that the tested fittings can be used in furniture constructions for joints which do not undergo significant dynamic or static loads in use such as shells of cupboards. The joints for chairs and tables, for example, should be better joined with glued joints or with special joining fittings.