The wide range of mechanical fittings developed for use with particleboard can be used just as effectively to join MDF panels. Some typical example are described.
Particleboard screws can be used for joining MDF panels in low stress applications. Recommendations relating to the insertion of screws in MDF should be noted, particularly with respect to the use of sufficiently large pilot holes to accommodate the solid core of the screw.
The principle components of this device are a hollow alloy cylinder which initially is a loose fit in the face of one half of the assembly and a hard metal pin anchored into the other. Although the outside of the cylinder is constant diameter and smooth, the wall thickness varies to provide the wall with the appearance of a circular wedge. In the wall there is a circumferential keyhole shaped slot which extends part of the way round the cylinder. The metal pin has a spherical head supported by a waisted portion of the pin. In order to use the joint the head of the pin is first inserted through the wall of the cylinder until the waisted part is located in the slot, then the cylinder is rotated with the wedging action of the wall drawing the metal pin further into the cylinder.
These connectors are made from plastic, with a metal locking screw. Both the dowel and the drum are held in their respective locations by the external ribbing. The dowel also has an internal metal pin which upon impact expands the bifurcated moulding into the core of the MDF. The angled metal locking screw within the drum both locks the head of the pin in position and draws the joint together.
Twin block fittings which are screw fixed to each panel and joined together with a single bolt are used to join furniture panels. By relying on face fixing of the plastics blocks, any tendency of the MDF to delaminate in the plane of the board is avoided. The simplicity of this fixing system is offset by the unsightly appearance of the blocks when placed in obvious positions.
|5.||The appearance limitations of twin block connectors can be avoided by using two face fixing inserts. This system is ideally suited to automatic insertion. The fitting is concealed by a plastic cover cap.|
The following general recommendations apply when using mechanical fixings in MDF.
1. Select fittings which depend upon face fixing wherever possible.
2. Avoid fittings which depend upon expansion of a component inserted into the board edge.
3. Sufficient clearance should be allowed for screws, dowels or other fittings inserted into board edges.