Chipboard: Types and Treatment
Chipboard is made by spreading resin-coated particles of wood, usually, on a flat plate and bonding them together under high pressure and heat.
Thicknesses of chipboard vary from 4 to 40 trim., but the most common available are 12, 18, 22 and 24 mm sheets are usually 2440 x 1220 mm (8 x 4 ft), but sizes up to 5200 x 1830 mm (17 x 6 ft) are made. Both British-made and imported varieties are widely available in several grades of hardness.
The fibres of the particles criss-cross, so that the board has similar strength and characteristics in all lateral directions, but the vertical structure is layered.
Most chipboard is now made in three or more alternating layers of fine and coarse particles, with fine particles on the faces.
There is also single-layer chipboard, which tends to have a coarse surface finish because large chips are used.
In extruded chipboard, which is now obsolete, the chips run from face to face and the board is easily snapped across its width. If you have any extruded chip- board, do not use it for furniture-making.
Modern multi-layer chipboards usually have sanded faces and some types are sealed and filled, ready for painting. There are also chipboards for special purposes, such as flooring, and veneered and melamine-faced chipboards.
Prices vary, but chipboard is generally half to two-thirds the price of.
Use: normal chipboard is for indoor use only and should not be used in damp conditions. Exterior-grade boards are not yet readily available.
Sawing and planing: use a panel, tenon, circular or jig saw. Finish the edges with a plane and glass-paper. Chipboard machines well, but wears cutters more quickly than softwood because of its resin
Jointing: chipboard can be jointed in the same way as solid wood but with one exception — do not make unsupported edge-to-edge joints to increase the width of a panel: the layered structure makes joints of this type very weak.
Fixing: always pin, nail andthrough chipboard. Never pin, nail or into the edge; the fixings will pull out easily.
Where hinges and other fittings have to be screwed to chipboard, fit solid timber lippings for piano-hinges, butt-hinges etc., and dowels for single fittings with only a few. dowels give the screws something solid to grip into and spread the load over a wide area.
Gluing: chipboard can be glued with any woodworking, but urea and thick PVA are best. The most effective bond is to the face. When lipping to the layered edge, use a tongued joint if possible, but a well-glued butt joint will do.
Storing: store sheets flat, but if space will not allow this, stand them on edge in a vertical position and secure them so that they do not become distorted.
This material, commonly used in furniture-making as a core in veneered sheets, is lighter than chipboard but is just as stable and slightly cheaper.
It is becoming more readily available in thicknesses of 19, 22 and 25 mm.
In 22 and 25 mm thicknesses, flaxboard is often used in its unsanded state as amaterial for mineral-felted roofs of garages etc., where it is nailed with large-headed galvanised clouts direct to the joists at 600 mm (24 in) spacings.
Flaxboard smells strongly of new-mown hay, unless completely sealed byor paint, and the smell can be overpowering in a confined space.