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Plastic is easy to drill, but it is also easy to melt, crack, or snag. The right bit depends less on the word “plastic” than on the material, hole size, and how clean the hole needs to be. For most small holes in common plastic, a sharp general-purpose twist bit works if you run it slowly and support the work. For larger holes or brittle sheet, bit geometry and careful setup matter more.
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Identify the plastic and the job
Acrylic and polycarbonate sheet can crack under pressure, especially near an edge. PVC and other softer plastics tend to cut readily but can soften from friction and clog the bit. Unknown plastics are best treated cautiously: start with a sharp bit, low speed, and a test hole in scrap if available.
Also consider the hole’s purpose. A clearance hole for a screw does not need the same finish as a visible hole in a sign or enclosure. For a screw going into plastic, the pilot hole should usually be sized to the screw’s core diameter, not its outside thread diameter. A pilot that is too small can split the plastic; one that is too large may leave the screw with little to grip.
Choose a bit for the hole
| Bit type | Best use | Trade-off |
|---|---|---|
| Sharp twist bit | Small holes, roughly 1/8 to 3/8 inch, in many plastics | Affordable and widely available; aggressive points can grab or crack thin, brittle sheet |
| Brad-point bit | Accurate small holes in softer plastic or plastic backed by wood | Centers well, but its spurs can catch brittle sheet or leave stress marks |
| Step bit | Round holes in thin sheet, especially when enlarging from a pilot | Often leaves a clean edge; limited to its step sizes and sheet thickness range |
| Hole saw | Larger holes in sheet or plastic panels | Useful for openings; needs a pilot, steady control, and frequent chip clearing |
For ordinary small holes, a sharp high-speed steel twist bit set is usually the sensible buy. Cobalt bits are not necessary for plastic. A step bit is worth considering for neat holes in thin panels, while a hole saw makes sense only when the opening is too large for a twist bit. A specialty plastic-drilling bit can reduce grabbing, but it is not essential for an occasional hole.
Set the drill and workpiece up correctly
Use a cordless drill in its low-speed range or trigger it gently. As a practical starting point, aim for about 500–1,000 rpm for small bits, and slow down further as the bit diameter grows. The exact safe speed varies with the plastic and bit, so treat this as a starting range, not a universal setting. High speed can melt the cut, smear chips across the edge, or make the bit grab when it breaks through.
Clamp the work securely, but do not crush it. Put a scrap board behind thin sheet to support the exit side and reduce breakout. Keep the drill square to the surface. A cordless drill’s clutch is useful when driving a screw into plastic, but drilling calls for the drill setting rather than a low clutch setting. Do not use hammer mode: its impacts can crack the workpiece. An impact driver is also a poor choice for drilling plastic because its pulsing action makes control and clean cutting harder.
Drill without melting or cracking
Mark the hole and, for brittle sheet, keep it well away from the edge. A cautious rule is to leave at least two hole diameters between the hole and the edge; more distance is safer for thin or stressed material. Avoid punching a deep center-punch mark in acrylic, which can start a crack. A light mark or a small pilot hole is safer.
Start with light pressure and let the bit cut. Back it out periodically to clear chips, especially in deeper holes. If the plastic starts to soften, forms long melted strings, or smells hot, stop and let the bit and work cool. Reduce speed and pressure before continuing. Do not force a dull bit: it creates more heat and tends to wander.
As the bit nears the back surface, ease off pressure. Breakthrough is a common cause of chipping because the bit can suddenly pull into the work. For a larger hole, drill a small pilot first, then use a step bit or hole saw at low speed. Clear debris between steps rather than pushing through a wad of chips.
Fit fasteners and finish the edge
For a screw into plastic, drill a pilot hole based on the screw’s core diameter and the material’s thickness. Test on scrap if the part matters. Tighten by hand or use a drill’s low clutch setting; stop as soon as the head seats. Over-tightening can strip the hole or split the plastic, and a washer can spread the load on thin sheet. If the screw must hold a meaningful load, use a through-bolt with washers or a suitable plastic-rated anchor rather than relying on threads cut into a thin panel.
Remove sharp burrs with a deburring tool, a countersink turned by hand, or fine sandpaper. Use a light touch: a powered countersink can quickly remove too much material or catch the edge. If a hole is visible, check the finish before enlarging it; a clean, slightly undersized hole is easier to correct than a cracked one.