3.Machining and processing HPL
Drilling tools
Drills for plastic materials are the most suitable for drilling in HPL. These are spiral drills with a point angle of approx. 60 – 80°, rather than 120° for normal metal drills. They also have a steep pitch with a large chip space. HSS drills are recommended for hand-held tools, TCT drills for machines with mechanical feed. Feed rate approx. 1500 – 3500 rpm. Multi diameter or step drills are suitable for stepped holes with different diameters, while cylindrical drills are suitable for holes with larger diameters.
Hole saws with guide drill can also be used and so-called adjustable hole saws with guide drill can be used for even larger diameters. For the latter, the hole should be cut from both sides if possible. Alternatively, larger cutouts can be made using a router with a template
1 Spiral drill | 2 Stepped drill | 3 Cylinder head drill | 4 Circle drill
Drilling technique
The penetrating speed of the drill has to be adjusted to avoid damaging the HPL. The cutting speed for HSS drills is approx. 0.8 m/s, for TCT drills up to 1.6 m/s. A feed of 0.02 – 0.05 mm/rev is considered suitable, i.e. for every 1000 revolutions the drill penetrates between 20 mm and 50 mm per minute. Using a hardwood or HPL base can prevent buckling of the material at the exit point of the drill. Even better results for series production can be achieved with drill gauges which have drill bushings on both sides and allow tight clamping of the workpiece. Speeds should be reduced by half for countersinking
