Techniques and equipment used to machine free cutting metals are generally suitable for plastics, as is most woodworking machinery. However, heat absorption and the resilience of many plastics call for some modification of general workshop practices. These notes, based on published data and practical experience, are offered as a guide.

• Plastics absorb heat. Because they are good thermal insulators, care must be taken not to overheat the workpiece. Heat in not easily dissipated.

• Plastics have high thermal co-efficients and often low melting points. Overheating will cause expansion, increase tool pressure and generate yet more heat.

• Plastics are not as 'stiff' as metals and, therefore, adequate support should be provided for the workpiece. Tools should have clearances to ensure that only the cutting edge is in contact with the material. Many plastics are also resilient.

• Nearly all plastics are notch sensitive. De-burring should always be carried out as a finished process.