Drilling Plastic
Special Scraping Drill Bits
Using a regular twist drill in plastic is a problem because the cutting edge takes too big a bite on each rotation of the drill. The best way to drill plastic is with special drill bits designed for plastic. These bits use a scraping action instead of slicing into the material, and they have a much more acute angle on the tip so that the hole is more gradually enlarged than with a metal cutting 118 or 135 degree bit. One brand is "Plexi Point," shown below.
Regular high speed drill bits can be ground to cut plastic. See this site for details.
Hole Saw
You can cut plastic with a hole saw, but the balance between enough force to cut and enough to melt the plastic is fine. Using water as a lubricant and coolant can help a lot.
Zero Flute Countersinks
We have had some success at enlarging holes using a zero flute countersink and cutting all the way through. The single cutting edge on these countersinks is not really scraping, but takes a controlled fine cut on each rotation.
