Plastic and acrylic crack, melt or grab if you drill them like wood or metal. The best drill bits for plastic use a modified point that shaves cleanly instead of biting in, so the bit does not snatch through and split the sheet at the moment it breaks the far side.
What to Look For
Acrylic and polycarbonate are brittle and heat-sensitive, and different plastics behave differently — cast acrylic is far more prone to cracking than tougher polycarbonate. A standard sharp twist bit tends to dig in and grab, cracking cast acrylic or corkscrewing the bit through as it exits the far side. Friction also melts plastic, welding gummy chips to the flutes and glazing the hole so the bit stops cutting and starts smearing. The goal is a scraping cut, controlled speed and good chip clearance. Look for a bit with a blunter tip and a less aggressive rake so it peels a clean ribbon rather than snatching, and pick a material that stays sharp so it slices instead of rubbing and overheating.
The Best Type of Bit for Plastic and Acrylic
A standard HSS twist bit works well once the tip angle is modified, or you can use bits specifically ground for plastics. The key is a blunter included angle and a slightly dulled leading edge so the bit peels rather than bites. Brad-point wood bits also give clean, controlled entry in softer plastics.
- Point angle: a blunter tip near 60–90° scrapes cleanly and resists grabbing in brittle acrylic.
- Speed: run slower to reduce heat; melting plastic clogs the flutes and ruins the hole.
- Feed: ease off as you break through the far side, where cracking and grabbing occur.
- Support: back the sheet with scrap and clamp it so it cannot flex or spin up the bit.
Avoiding Cracks and Melt
Peck-drill deeper holes to clear chips and let heat escape between passes. If chips come off gummy, stringy or welded together, you are running too fast — slow down until you get discrete curls. For a truly clean edge on thick acrylic, deburr or lightly countersink the hole afterward to relieve stress that could later propagate a crack. American-made HSS bits give the consistent, precisely ground geometry that clean plastic drilling depends on, so results stay repeatable across a run of parts.
Choosing the Right Size
Plastics expand and contract with temperature and swell around a tight fastener, so slightly oversize clearance holes prevent stress cracks down the road, especially on parts left outdoors in the sun. Never thread a screw hard into a tight hole in acrylic without some relief, and avoid over-tightening, which locks in stress that later finds its way to a crack. When two plastic parts must bolt together, an oversize hole in at least one lets them move without binding. Our selection guides help you pick the right diameter and bit style for the plastic you are working, so the finished part holds up instead of splitting weeks later.