Proper Drill Bit Angle and Speed for Drilling Plastic

Drill Bits

• A drill bit that is specially designed to penetrate plastic has a sharp tip and two large channels up the sides. The angle of the point is narrower than on drill bits for wood and masonry to cut through plastic better without jerking it around. "Plastics Distributor & Fabricator Magazine" recommends choosing or grinding a bit point to between 60 and 90 degrees. Acrylic bits may have a diamond dust coating that helps the tip penetrate the plastic more smoothly, reducing chipping and cracking.

Drill Speed

• When hard plastic meets the metal drill bit, it generates a lot of friction on the bit, causing it to heat up quickly. The heat can even melt the plastic right around the bit, creating a hole that is bigger than the diameter of the drill bit. When drilling into plastic, always drill slowly at low to medium speed and pause frequently. This allows the bit and the plastic to cool back down to workable temperatures. Try drilling a small pilot hole in the plastic first then using the larger bit. This will mean less stress on the bit and the drill, along with less friction.

Coolant

• Because of the heat generated between the plastic and the bit, use some kind of liquid to keep temperatures down. Lubricate the bit and the hole with either water or a water-based oil. This lubrication is used as cutting fluid and gives the holes smoother sides.

Angle

• The drill bit should be held perpendicular to the surface of the plastic to take advantage of the sharp point needed to penetrate it. When the bit is properly sharpened, lubricated and held at the proper angle when you drill, two strips will spiral out from the channels in the bit. This is a good sign that the drill bit is making a smooth hole. Clamp the plastic to the work table to keep it still and place a piece of wood under it to accept the drill bit when it punctures the plastic completely. This can prevent chipping and splitting on the bottom part of the hole.