Learn How to Drill a Clean Hole in Acrylic Successfully

Drill a clean hole in acrylic by using a bit ground to a 90-degree point angle and a 0-degree rake angle, backing the sheet with scrap wood, and pecking the drill in and out for holes deeper than the bit’s diameter. The hole center must be at least 1.5 times the hole diameter from the sheet edge, and bolt holes need a diameter twice the bolt size for expansion clearance.

The 90-degree angle is the difference between a clean exit and a spiderweb crack. A standard 118-degree metal bit acts like a wedge, prying the material apart from the inside. The flatter 90-degree point slices through, and the 0-degree rake scrapes instead of gouges. Get that wrong, and the last millimeter of the hole blows out.

What follows is the geometry, the feed rate, and the spacing that keeps acrylic intact. It’s not about going slow. It’s about matching three specs printed in OEM manuals that most DIY guides skip.

Key Takeaways

• A standard metal drill bit will crack acrylic. You need a bit reground to a 90-degree point angle and a 0-degree rake angle.
• For any hole that will hold a screw or bolt, the drilled diameter must be at least twice the fastener’s diameter.
• Keep the center of your hole at least 1.5 times the hole’s diameter away from the edge of the sheet.
• For holes deeper than the bit’s diameter, you must use a pecking motion and water cooling to clear chips and prevent melting.
• Always back the acrylic with a sacrificial piece of wood or MDF to prevent blowout on the exit side.

The Right Drill Bit Is Not What You Think

Forget the drill. The bit is the whole job. A standard high-speed steel twist bit meant for metal has a 118-degree point. That sharp angle is designed to cut steel, but in acrylic, it acts like a chisel. It pushes material outward instead of shearing it, and the last bit of uncut material at the exit point snaps under the pressure.

ACRYLITE’s fabrication brief states that for most sheet drilling, bits with a 90-degree tip angle should be used. This generates smaller chips for easier evacuation and reduces the risk of cracking and blowout as the bit exits.

You need a bit ground for plastic. The specs are non-negotiable: a 60- to 90-degree point angle, a rake angle ground flat to between 0 and 4 degrees, and a clearance angle behind the cutting edge of 12 to 15 degrees. A 0-degree rake angle means the cutting edge scrapes the acrylic instead of digging into it. This prevents the bit from grabbing and shattering the sheet.

Brands like Fisch and Bosch make off-the-shelf brad-point bits for plastic that meet these specs. The LP Aero Plastics acrylic drill bit is a known, reground option. For a one-off job, you can modify a metal bit by carefully grinding the cutting edges flat on a bench grinder. It’s a fussy job, but it beats buying a new sheet.

Bit Type	Point Angle	Rake Angle	Best For	Risk If Wrong
Standard HSS (Metal)	118°	Positive (~15°)	Steel, Wood	Chips and cracks exit side
Modified Acrylic Bit	90°	0° to 4°	Acrylic, Plexiglas	None if geometry is correct
Carbide Tipped	90°	0°	Production runs	Expensive, brittle on hand drills
Brad-Point (Wood)	60°-90°	Variable	Not recommended	Can grab and crack sheet

The helix angle, the twist of the flutes, matters too. A moderate 15- to 30-degree helix helps pull chips out. A low helix angle lets chips pack in the flutes, melt from friction, and weld themselves to the hole wall. You’ll smell burning plastic before you see the cloudy, rough bore.

Speed, Feed, and the Pecking Drill

Drill speed is measured in surface feet per minute (SFM), but your drill has an RPM setting. For a 1/4-inch bit in acrylic, you want between 20 and 160 SFM. That translates to roughly 300 to 2500 RPM. Start at the low end.

Feed pressure is the silent killer. The weight of a cordless drill is often enough. Push harder, and you generate heat. The acrylic’s low thermal conductivity traps that heat right at the cutting edge. The material expands, grips the bit tighter, and melts.

Where this goes sideways: Forcing the bit. If you see long, continuous spirals coming out of the hole, you’re feeding too fast and generating too much heat. The chips should be small, powdery fuzz.

For any hole deeper than the bit’s diameter, you must peck drill. Drill in about one diameter’s depth, pull all the way out to clear the chips, then go back in. This isn’t optional. It’s the only way to keep the flutes clear and coolant reaching the tip. For manual drilling, this is the step every impatient builder skips. The hole walls turn cloudy and rough halfway down because packed chips are rubbing, not cutting.

Step 5: Cool It Down (Or Don’t)

Coolant does two things: it keeps the bit and acrylic from overheating, and it flushes chips out of the hole. For thin sheets under 1/4 inch, you can often get away with no coolant if you peck and use the right bit. Go thicker, and you need it.

PLEXIGLAS’s guide says tap water is fine. Use a spray bottle. A couple of spritzes into the hole every few pecks works. Don’t flood it. The goal is to keep the temperature below the glass transition point where acrylic gets gummy, around 105°C (221°F).

If you’re drilling on a drill press, a drip system is better. But for a hand drill, the spray bottle and pecking rhythm is the field fix. The moment you see smoke or smell that sweet, acrid burn, stop. You’ve already damaged the hole.

Hole Placement and Sizing Are Not Suggestions

You can drill the perfect hole in the wrong place and still crack the sheet. Acrylic expands and contracts with temperature changes more than the metal fastener you’re putting through it. If the hole is too small or too close to the edge, the stress has nowhere to go.

The two rules from ACRYLITE’s engineering guide are specific: 1. Bolt Hole Diameter: At least 2 times the diameter of the bolt or screw. 2. Edge Distance: The hole center must be at least 1.5 times the hole diameter from the sheet edge.

Drilling a hole for a #8 screw (0.164″ diameter)? Your pilot hole should be at least 0.328″, or 21/64″. And the center of that 21/64″ hole needs to be no closer than (1.5 * 0.328) = 0.492″ from the edge.

Skip these rules for a shelf bracket, and the first hot day will push against the fastener. A hairline crack starts at the hole and runs to the edge. It might take a season, but it will happen.

The 7-Step Manual Drill Process

This is for a cordless drill and a single hole. A drill press is more precise, but most people don’t have one bolted to their workbench.

1. Mark and Punch. Use a fine-point permanent marker on the masking film. Hit the center with a center punch to create a small dimple. This keeps the drill bit from walking.
2. Secure the Work. Clamp the acrylic to your workbench. Put a sacrificial backing board, scrap plywood or MDF, underneath. This is your blowout guard.
3. Set the Speed. Start at a low RPM. For a 1/4″ bit, that’s around 800 RPM on your drill’s variable trigger.
4. Start the Hole. Hold the drill perfectly perpendicular. Apply light pressure and start the hole. Let the bit’s point find the dimple and begin cutting.
5. Peck and Clear. Drill in about 1/4″, pull all the way out to clear chips, spray a little water in the hole, and repeat. Listen. A quiet, steady hum is good. A high-pitched whine means slow down.
6. Mind the Exit. As the bit tip breaks through the backside, reduce pressure to a feather touch. Let the backing board take the final push.
7. Deburr Both Sides. Use a countersink bit, a larger drill bit by hand, or fine sandpaper to break the sharp edge around the hole on both the entry and exit sides. A sharp edge is a stress concentrator and a crack starter.

Common mistake: Drilling the hole, then removing the clamps to deburr. The thin, flexible sheet can flex as you press on it with a countersink, cracking radially from the hole. Deburr it while it’s still clamped down.

When to Step Up Your Tools

A hand drill works for one or two holes. For more, or for larger diameters, your approach changes.

• Hole Saws: Use only for thin sheets (under 1/4″). The tooth pitch must be fine. Run slow, use lots of coolant, and clear the teeth of packed chips every few seconds.
• Step Drills (Unibits): Excellent for thin sheets and creating clean, cylindrical holes. They generate less grabbing force than a standard bit.
• Drill Press: The game changer. It guarantees perpendicular holes and consistent feed pressure. If you’re drilling more than five holes, set up a press.

For a hole over 1 inch, don’t try to drill it in one shot. Drill a pilot hole, then use a circle cutter or a fly cutter on a drill press. The ACRYLITE manual specifies a spindle speed of 400-600 RPM for circle cutters and insists the bit must be modified to a 0- to 4-degree rake angle to scrape, not cut.

Troubleshooting Cloudy, Melted, or Cracked Holes

You followed the steps and it still went wrong. Here’s what happened.

Cloudy, rough hole walls: Chips melted and re-solidified inside the hole. The feed rate was too high, the speed was too low, or you didn’t peck and cool. The bit’s flutes were packed.

Spiderweb crack on exit: The bit’s point angle was too steep (118 degrees), or you forced the feed on exit. The acrylic flexed downward before the point broke through, creating tensile stress that cracked it.

Hole is oval or oversized: The drill wandered. You didn’t use a center punch, or the drill was not held perpendicular. For larger holes, not using a pilot hole causes this.

Long, stringy chips: The rake angle is positive. The bit is digging in and lifting ribbons of material instead of scraping it into powder. This creates more heat and increases the chance of grabbing.

If the hole is just cloudy, you can sometimes salvage it by carefully reaming it with the same bit, using perfect technique and plenty of coolant. A cracked hole is a loss. Drill a new one in a new location, following the edge distance rule.

Frequently Asked Questions

Can I use a regular drill bit on acrylic?

You can, but you risk cracking it. A standard 118-degree metal bit is designed to cut metal, not plastic. It pushes material outward and can act like a wedge, especially on the exit side. If you must use one, grind the cutting edges to a flat, 0-degree rake angle first.

Why does my drill bit keep grabbing and cracking the acrylic?

The bit is grabbing because its rake angle is positive, it’s digging in like a shovel. Acrylic bits have a 0- to 4-degree rake, so they scrape. Also, too much feed pressure or a dull bit will cause grabbing. Ease up and let the bit do the work.

How do I drill a large hole in acrylic, like for a pipe?

For holes over 1 inch, a hole saw or circle cutter is the right tool. Use a fine-toothed hole saw, run it at a low speed (under 500 RPM), and use constant coolant. A circle cutter on a drill press is better, as it puts less stress on the material. Always drill a pilot hole first for the center arbor.

Do I need a special drill, or is my cordless drill okay?

Your cordless drill is fine. The tool is less important than the bit and the technique. A drill press is superior for control and perpendicular holes, but for most DIY jobs, a steady hand, a sharp acrylic bit, and a clamped workpiece are all you need.

What’s the best way to drill acrylic without cracking it?

Use a drill bit ground for plastic (90-degree point, 0-degree rake), clamp the sheet to a backup board, drill at a low to medium speed with very light pressure, and use a pecking motion with water cooling for any hole deeper than the bit’s width. The backup board is critical to prevent exit chipping.

Before You Go

Drilling acrylic cleanly comes down to respecting the material. It’s brittle, it expands, and it melts easily. The right bit geometry, a 90-degree point and a scraped edge, turns a risky job into a routine one. Clamp it down, peck your way through, and give that hole plenty of room from the edge. Your first perfect, glass-clear hole is the only proof you need.