This Kitronik University course is part of the working with materials course, and covers aspects of machining and routing Perspex.
Machining
Perspex® is a brittle material. It is, therefore, necessary that only light machining cuts are taken and feed rates kept slow. Perspex® will soften if heated above 80°C and heat build-up can cause stress. Therefore, the use of coolants, including water and compressed air, in particular, is recommended during machining operations. Perspex® can also be turned on a conventional metalworking centre lathe with cutting speeds to be reduced for an improved quality finish. For turning, HSS tool bits are preferred, kept sharp and ground to zero rake at the top and with 15-20° front rake. Stress generated by machining can lead to stress-cracking or crazing either immediately or some time after machining. However, stress can usually be reduced, else eliminated in some materials by the gentle heat conditioning process of annealing.which is a gentle heat conditioning process. While annealing may be required, if machining Perspex® cast to very close tolerances, it may be necessary to normalise the sheet in order to remove the casting stresses from the products manufacture, which would ordinarily have no effect on the behaviour of the product. By heating the Perspex® above its glass transition temperature, the stresses are relaxed giving rise to uniform shrinkage of approximately 2%. Normalised Perspex® would therefore, be fully stress-relieved.Routing
Fixed head, moving head or portable standard woodworking routers are suitable for Perspex® using the same cutter speeds as for wood. Routing can actually be performed dry but all swarf must be cleared and the cutter kept cool. Compressed air directed onto the cutter and work-piece would be preferred. For routing, HSS double-edged cutters are preferred, ground and honed with a back clearance angle of about 12° or greater. See table below for cutter speeds.| Cutters | Spindle Speed |
| 6-12mm Diameter or less | ca 24000RPM |
| >12mm | ca 18000RPM |
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