How To Drill Plastic

Plastic is deceptively tricky. It looks easy — smooth, uniform, cooperative — but push the wrong drill bit into it at the wrong speed, and the whole piece shatters like a bad promise. Whether you’re working with acrylic sheets, PVC pipes, polycarbonate panels, or everyday ABS plastic, the difference between a clean hole and a cracked mess comes down to a handful of precise decisions.

This guide covers every one of them.

Why Plastic Behaves Differently

Unlike wood or metal, plastic is thermally sensitive and structurally unforgiving. It doesn’t absorb heat — it holds it. That stored heat melts the surface around your drill hole, warps the edges, and introduces stress fractures that grow invisibly until the piece snaps days later.

Plastic also lacks the fibrous grain of wood to guide a bit naturally. Without proper centering technique, a drill can “walk” across the surface before it even bites, scratching the finish or starting the hole in the wrong place.

Understanding these two characteristics — heat sensitivity and surface instability — is the foundation of every good drilling technique that follows.

Know Your Plastic First

Not all plastics drill the same way. A method that works beautifully on polyethylene can destroy acrylic in seconds. Matching your approach to the material is the single most important step before you pick up a drill.

The Right Drill Bits for Plastic

Choosing the right bit is like choosing the right scalpel — precision starts before you touch the surface. Using the wrong bit doesn’t just risk cracking; it generates excess heat, rips the material, and leaves ragged holes that require hours of cleanup.

Brad Point Bits

Brad point drill bits are the top overall choice for plastic. The sharp center point locks onto your marked spot before the flutes begin cutting, eliminating the “walking” problem entirely. They pull clean chips away from the hole rather than compressing plastic debris into the edges, which reduces both heat and cracking risk.

HSS (High-Speed Steel) Bits

HSS drill bits are the most widely available option and handle most common plastics effectively. They’re durable, sharp, and heat-resistant — but they dull faster than carbide options, especially with abrasive composites. Use them with light lubrication to extend their life.

Step Drill Bits

The step drill bit is the Swiss Army knife of plastic drilling. One bit drills holes of multiple diameters, and its graduated cone shape enters the material gradually — spreading cutting pressure across a wider area and dramatically reducing the chance of cracking thin sheets.

Carbide-Tipped Bits

For hard engineering plastics like PEEK, polysulfone, or polymer composites, carbide-tipped bits are non-negotiable. Carbide stays sharp under punishing conditions and handles the abrasive fillers found in reinforced plastics that would destroy an HSS bit within minutes.

Auger Bits

Auger drill bits use a screw-like design that physically pulls material out of the hole as they cut. They’re best suited for softer plastics where clean chip evacuation matters more than fine precision.

Tools and Materials You’ll Need

Before drilling a single hole, gather everything. Stopping mid-process to hunt for supplies is how mistakes happen.

• Variable-speed drill (corded or cordless)
• Appropriate drill bit for your plastic type
• Clamps or a bench vice for securing the workpiece
• Scrap wood backing board
• Pencil or fine-tip marker
• Center punch or awl (optional, for marking)
• Masking tape
• Lubricant — water, machine oil, or plastic cutting fluid
• Safety glasses
• Fine-grit sandpaper or a deburring tool

Step-by-Step: How to Drill Plastic Cleanly

Think of this process as a rhythm — preparation, patience, controlled execution. Rush any step, and the plastic will punish you for it.

Step 1 — Mark Your Hole Precisely

Use a fine-tip marker or pencil to mark the exact center of your intended hole. For extra precision on smooth, shiny plastics, place a strip of masking tape over the surface first — it gives the marker something to grip and prevents the drill tip from skidding at the start.

Step 2 — Secure the Plastic

Never drill plastic freehand. Place the workpiece on a flat, stable surface and clamp it firmly. For thin sheets, sandwich the plastic between two pieces of scrap wood — one on top, one underneath. This distributes drilling pressure evenly and prevents the underside from splintering as the bit exits.

Step 3 — Place a Wood Backing Board

Slide a piece of scrap wood beneath the plastic before you drill. When the bit breaks through the far side, it enters the wood rather than tearing the plastic edge. This one simple step eliminates the vast majority of exit-side chipping and cracking.

Step 4 — Drill a Pilot Hole

For holes larger than 6mm (¼ inch), always drill a pilot hole first. Use a small bit — roughly half the diameter of your final hole — at slow speed. This gives the larger bit a centered guide and significantly reduces lateral stress on the surrounding plastic.

Step 5 — Set Your Drill to Low Speed

Slow speed is non-negotiable with plastic. High RPM generates heat, and heat in plastic means melting, crazing, or stress fractures. For most plastics, aim for 300–800 RPM to start. Only increase speed once the bit has fully bitten in — and even then, modestly.

For reference: ABS tolerates 165–650 ft/min cutting speed; polycarbonate is best kept to 165–320 ft/min; materials like polysulfone and Ultem need a conservative 65–260 ft/min.

Step 6 — Apply Light Lubrication

Before you start cutting, apply a small amount of water, light machine oil, or cutting fluid to the drill point and the marked surface. This isn’t optional with thicker workpieces — lubrication reduces friction, dissipates heat, and keeps your bit sharper for longer. Water works well for most thermoplastics; avoid oil-based lubricants on some materials like polycarbonate, which can be chemically sensitive.

Step 7 — Drill With Steady, Gentle Pressure

Hold the drill perpendicular — 90 degrees to the surface at all times. Apply consistent, gentle downward pressure. Let the bit do the cutting; forcing it does nothing except build heat and stress. If you feel resistance, ease off pressure and let the bit recover.

Step 8 — Use Short Bursts, Not Continuous Drilling

Drill in short 2–3 second bursts rather than continuous cutting. Each pause lets the plastic cool slightly and allows chips to clear from the flutes. This peck-drilling technique is especially important for holes deeper than 3–4 times the bit diameter.

Step 9 — Reduce Pressure as You Exit

As the bit approaches the far side, ease your downward pressure significantly. This is the highest-risk moment — the remaining thin wall of plastic is vulnerable to blowout. A backing board handles most of this risk, but reduced pressure provides the final layer of protection.

Step 10 — Deburr and Finish the Hole

Once drilled, remove burrs along the hole edge with fine-grit sandpaper, a deburring tool, or a larger drill bit turned by hand. Smooth edges aren’t just cosmetic — jagged burrs create stress concentration points that cause cracks to propagate under load over time.

Drilling Specific Plastic Types

Acrylic (Plexiglass)

Acrylic is the most unforgiving plastic to drill. It shatters under vibration and crazes when overheated. Use a brad point bit with a 0° rake angle — standard twist bits will grab and crack it. Keep RPM low, use masking tape on both faces, and always use a wood sandwich. Never apply sudden pressure.

PVC Pipe and Sheet

PVC is more forgiving than acrylic but melts readily. Use sharp HSS bits at moderate speed, keep cuts short, and allow cooling between passes. Avoid letting the bit sit stationary in the hole — the friction heats the plastic and the bit simultaneously bonds to the edges, making extraction difficult.

Polycarbonate

Polycarbonate is tougher than acrylic and more resistant to impact, but it still cracks under improper drilling. Use brad point or carbide bits at 165–320 ft/min cutting speed. Avoid oil-based lubricants; use water-based cutting fluid instead.

HDPE and Polyethylene

These soft plastics are prone to grabbing — the bit catches on the soft material and spins the workpiece suddenly. Secure HDPE aggressively before drilling. An auger bit works well here because its screw action pulls material away before it can grab the flutes.

Drilling Speed Reference Table

Common Mistakes That Wreck Plastic

Even experienced DIYers fall into these traps. Recognizing them before you start is far cheaper than replacing a cracked acrylic sheet after.

• Drilling too fast — the most common mistake; heat melts and deforms the plastic around the hole
• No pilot hole for large diameters — the bit wanders and splits the material at entry
• No backing board — exit-side blowout is almost guaranteed without one
• Using dull bits — a dull bit compresses rather than cuts, generating enormous heat
• Drilling without securing the workpiece — vibration causes micro-fractures that grow into visible cracks
• Continuous drilling without breaks — heat accumulation in deep holes causes crazing and dimensional changes
• Wrong bit for the material — using spade or paddle bits on plastic is a recipe for immediate cracking

Safety First

Drilling plastic generates sharp chips and, if overheated, toxic fumes from some materials. These precautions aren’t optional:

• Wear safety glasses — plastic chips travel fast and far
• Work in a ventilated space — burning or melting thermoplastics release irritants
• Wear gloves when handling freshly cut plastic — edges are razor-sharp before deburring
• Secure all workpieces — a spinning, unsecured piece of plastic is genuinely dangerous
• Never force a stuck bit — reverse the drill at low speed to back it out cleanly

Key Takeaways

• Slow speed is the single most important variable — high RPM generates heat that melts or cracks plastic every time
• Brad point bits give the cleanest, most precise results on most plastics; carbide bits handle hard engineering plastics
• Always back the workpiece with scrap wood and clamp it firmly before drilling
• Use pilot holes for anything larger than 6mm, and drill in short bursts to manage heat in thicker materials
• Match your technique to the specific plastic type — what works on HDPE can shatter acrylic in seconds

Frequently Asked Questions (FAQ)

What is the best drill bit for drilling plastic without cracking it?
Brad point drill bits are generally the best choice for most plastics because their sharp center point prevents the bit from walking across the surface. For hard engineering plastics like PEEK or polymer composites, carbide-tipped bits are more durable and stay sharp longer. Avoid wood spade bits or paddle bits entirely — they create excessive lateral stress that splits plastic.

Can I drill plastic with a regular metal drill bit?
Yes, HSS twist bits designed for metal can work on plastic, but with caution. They lack the ideal geometry for plastic and can generate more heat than a dedicated plastic bit. If you use an HSS metal bit, keep the speed very low, use lubrication, and drill in short bursts. Never use a dull bit — sharpness matters more with plastic than almost any other material.

How do I stop plastic from cracking when drilling?
The key is combining four protections: use a sharp brad point or step bit, back the plastic with scrap wood, drill at low RPM, and apply gentle, consistent pressure. Creating a pilot hole first for larger holes also dramatically reduces crack risk by guiding the larger bit and minimizing the entry stress on the plastic surface.

What speed should I use when drilling into plastic?
Most plastics drill cleanly between 300 and 800 RPM — well below the speeds you’d use for wood or metal. Brittle materials like acrylic need the slowest settings; softer materials like polyethylene tolerate slightly higher speeds. When in doubt, start slow and increase gradually only after the bit has fully engaged the material.

Why does my drill bit melt the plastic instead of cutting it?
Melting almost always means too much heat — caused by high drill speed, dull bits, or drilling continuously without breaks. Reduce RPM immediately, check that your bit is sharp, and switch to peck drilling (short bursts with pauses to cool). Applying a water-based lubricant to the drill site also significantly reduces thermal buildup.

Do I need lubricant when drilling plastic?
For thin plastic under 6mm, lubrication is helpful but not always essential. For thicker pieces, hard engineering plastics, or deep holes, lubrication is strongly recommended. Water is the safest and most universally compatible option. Avoid petroleum-based oils on polycarbonate, as they can cause stress cracking in that specific material.

When should I use a step drill bit instead of a twist bit for plastic?
Use a step drill bit when you need to drill a large hole (typically over 10mm) in a thin plastic sheet. The stepped cone design gradually widens the hole rather than punching through all at once, which is far less likely to crack or shatter thin material. Step bits are also ideal when you need multiple hole sizes in one project — one bit replaces an entire set.