how to cut and use
Plastics sheets show many of the characteristics of composite wood-based boards. Most woodworking tools can be used, providing they are kept sharp. The biggest problem is frictional heat, which causes the plastic material, especially swarf, to melt. The HIPS sheets are particularly susceptible to melting. The general rule is, 'fast speed, slow feed', and if necessary use water based cutting fluids. Plastics materials expand when they are heated and contract on cooling. For all except the Yoghurt and Charcoal this can be as much as 2mm per m over a 10 degree temperature change.
Sheets will scratch if handled roughly, so care should be taken when they are being moved and stacked, especially when they are laid flat on the floor or a worksurface. They will also bend if stacked badly, but stacking 'in the other direction' will normally return bent sheets to their original shape. The HDPE bottle range bend more than the HIPS ones. Metal clamps should have a softer buffer to avoid indentation of the sheet surface.
Holes up to 25 mm diameter can be made with standard tools; trepanning tools should be used for larger holes. Drills should be kept sharp, and the drill regularly withdrawn to ensure that melting is not taking place at the point - the 'woodpecker' method. A point angle of at least 100° should be used. Special drills for plastics are available with fast helices and polished flutes. Cooling should be by air blast as a minimum, water or emulsions are preferable, oil based coolants should be avoided. Liquids should be washed off with water after machining.
Milling machines and woodworking routers can be successfully used on HDPE boards, but are difficult with the HIPS range. Sharp tools and a relatively slow feed rate give the best results. To prevent chatter, care should be taken to ensure that work is securely clamped using broad, soft faced jaws.
Most saws can be used to cut our plastic board, fine teeth are preferred. A wavy set or skip tooth saw is recommended to ensure that the friction from the face of the blade is kept to a minimum and that swarf is rapidly removed. Reciprocating blade saws (e.g. jig saws) can generate heat and attention should be given to swarf removal and blade cooling, especially with HIPS. For circular saws, TCT blades are preferred, the kerf width should be greater than the blade, with deep gullets, all helping to reduce friction and remove swarf speedily.