We have a look at Norbord MDF installation guidelines.
Mechanical joints and fixings
Mechanical fittings developed for use with particleboard can be applied to CaberWood MDF with the following recommendations:
- Wherever possible, select fittings that depend upon face fixing
- Avoid fittings which depend upon the expansion of a component inserted into the board edge
- When using screws follow the pilot hole dimensions recommended below
Use screws with the non-threaded core of a similar length to the thickness of the panel being jointed
The internal bond strength of CaberWood MDF gives substantially better screw holding over other types of panel products.
Type of screw
Most types of screw can be used. Best results are obtained with parallel thread screws and a high overall diameter-to-core ratio is desirable.
Screws which are inserted into the face should not be less than 25mm from the corners. Screws inserted into the edge should not be less than 70mm from the corners. Do not over-tighten screws as further turning after screws are tight will reduce the holding power.
Larger diameter pilot holes than those recommended for solid wood and particleboard are required in faces and edges of MDF to accommodate the core of the screw. For GKN Superscrews, the recommended pilot diameter should be 85% to 95% of the screw core diameter.
This requirement is particularly important when screwing into the edges
of thinner boards. Pilot holes should be drilled approximately 1mm beyond
the expected depth of insertion of the screws into the board.
Dowel holes should be machined with a sharp tool so that the surfaces are free from loose fibre. All dust should be removed prior to assembly. The dowel hole diameter should be slightly larger than the dowel as this will allow good adhesive cover and avoid splitting of the edge. Dowels with multiple longitudinal or spiral groove patterns ensure uniform adhesive spread within the joint. For best results, dowels should be given a total glue coverage; adhesives such as Polyvinyl Acetate (PVA) or Urea Formaldehyde are preferred as they have good gap filling properties while their high solid content counteracts absorption of adhesive into the machined edges of CaberWood MDF.
Nailing and stapling
Where other methods of fixing are not practical, CaberWood MDF can be fixed with nails. Nails should be spaced 150mm apart to reduce the risk of splitting and at least 70mm from the corners. Nailing the edges of 9mm and 12mm CaberWood MDF is not recommended because of the risk of splitting
CaberWood MDF can also be fixed using staples. For best results, staples should not be inserted closer than 12mm from the edges and 25mm from the corners. This fixing method is only recommended for applications involving light loads. Close spacing of the staples is acceptable but the legs should be aligned at an angle of 15° to the plane of the board.
Mitre joints between CaberWood MDF panel.
Adhesive bonded joints
A wide variety of jointing methods can be adopted providing the following simple guidelines are observed:
- The joint parts should be accurately machined
- Sharp cutters should be used to avoid tearing or burnishing the surfaces to be bonded
- A high solids content adhesive with gap filling properties should be used. (Polyvinyl Acetate or Urea Formaldehyde)
- Mating pieces should be accurately located and held under pressure while the adhesive is setting
- The width of grooves machined in CaberWood MDF should be limited to about one third of the thickness of the board
- The depth of groove should be about one half of the board thickness
- Adhesive bonded joints should be allowed to condition for several days before sanding and finishing to avoid the appearance of sunken joints. This treatment is essential when using high gloss finishes
- A tongue and groove joint is very efficient, provided the fit of the joints is not too tight as this may cause a split along the edge
- When attaching lippings the tongue should be machined on the solid wood piece
CaberWood MDF can be fixed using conventional dry lining techniques. For best results, follow these recommendations:
- Before fixing, condition the board for a minimum of 24 hours in the area of use
- An expansion gap of 10mm or 2.5mm per metre (whichever is the greater) must be allowed, on length and width