Optimization of Double Thread Nuts Screwing Process

The construction of furniture corner joints is often carried out by assembling double thread (“Trio”) nuts and metal corners. Such connections are particularly suitable for disassemble bal structures and these connections are also used for savings in transport when all the structural elements are transported in boxes and furniture is prepared for in site assembly. The assembly process consists of fastening the binding metal corners to wooden elements with the metric thread screws. To achieve the optimal quality of these joints, the production process must comply with the requirements of various products including the loading applications and strength of individual wood species. This paper examines the fundamental factors affecting the quality of such joints. Special attention was paid to the process of screwing and loading capacity of double thread nuts in three different types of wood. Optimization of the technological process was set as the ultimate goal aimed at achieving a high level of product quality. Tests have been conducted on fi r, beech and oak wood to determine optimal bore diameters and nut screwing parameters relative to the screwing resistance, extraction force and the time interval required for nut screwing.