How to Drill Asphalt: Best Asphalt Drill Bits & Core Drilling Techniques

Asphalt drilling is the process of creating precise holes in asphalt surfaces, a task vital for roadwork, pavement maintenance, and underground installations. 

Whether it’s installing utility lines, testing pavement quality, or performing targeted repairs, this technique ensures projects stay on track and utilizes the best products. Its importance lies in its ability to support infrastructure development and upkeep without compromising the asphalt’s integrity.

However, asphalt drilling isn’t without its challenges. Unlike concrete, asphalt is softer, yet it demands precision to prevent cracking and surface damage, unlike concrete drill bits. Also, standard drill bits won’t work—asphalt’s unique texture requires specialized drill bits designed to cut cleanly and efficiently.

This guide is here to help you continue overcoming these hurdles with confidence. Here’s what we’ll cover:

• The best asphalt drill bits and core drills for various applications
• A step-by-step guide to drilling asphalt safely and effectively
• Common mistakes to avoid and troubleshooting tips to keep your project running smoothly

By the end, you’ll have the know-how to tackle asphalt drilling like a pro, ensuring successful outcomes every time. Let’s get started! 

What Is Asphalt Drilling & Why Does It Matter?

Asphalt drilling means making exact holes or taking samples from asphalt roads with special machines. It’s used for things like installing utility lines (think electrical or drainage systems), testing pavement, or making specific repairs. 

For example, when drilling through asphalt on highways, contractors must be careful not to mess up the concrete underneath. Engineers use samples to check if the asphalt meets standards like ASTM.

Choosing the Right Tools

• Carbide-tipped bits: Great for small holes in thin asphalt without breaking the bank.
• Diamond-core bits: Perfect for tough jobs, like drilling through thick asphalt mixed with concrete.
• Core extraction bits: These are Used to take samples without damaging the asphalt.

Good asphalt drilling saves money over time by ensuring longevity and preventing extra damage during setups. It keeps the pavement strong and stops water from sneaking in, which can lead to potholes. For pros, mastering this skill means following safety rules and meeting project goals in big jobs.

Choosing the Best Drill Bit for Asphalt

Picking the right drill bit sizes and lengths is key to making your asphalt drilling project a success. With different options out there, it’s all about finding the one that fits your job. Here’s a simple rundown to help you choose.

Types of Drill Bits for Asphalt

Carbide-Tipped Drill Bits

These are great for small holes and lighter jobs. They’re affordable and work well on thin asphalt where you don’t need to drill too deep, especially considering the length needed for the task. A solid choice here is the Bosch Asphalt Masonry Drill Bit—it’s durable and spot-on for smaller tasks.

Diamond-Tipped Drill Bits

Got a bigger or tougher job? Go for diamond-tipped bits. Their diamond coating cuts through asphalt smoothly, giving you clean holes without cracks. They’re capable and perfect for large holes or deep drilling. Pros swear by the Hilti Diamond Asphalt Drill Bit for its awesome performance.

Asphalt Core Drill Bits

Need to pull out a core sample or make a big hole? Asphalt core bits are your answer. They cut out a full chunk of asphalt without wrecking the surface—ideal for testing or big installations. The BLUEROCK Asphalt Core Bit is a trusty pick, even for rough jobs.

Wet vs. Dry Drilling

The way you approach drilling—wet or dry—can change how your project turns out. Here’s the scoop:

Wet Drilling

Wet drilling uses water to keep the bit cool and cut down dust, making it one of the top products for thick asphalt. It’s awesome for thick asphalt because it helps the bit last longer and makes cleaner cuts. You’ll need water handy and a drainage plan, though. The Hilti DD-BI Asphalt Core Bit is made for this and works like a charm.

Dry Drilling

Dry drilling skips the water, so it’s faster to start and clean up. It’s best for thin asphalt and quick jobs, but you’ll need to use a vacuum to deal with the dust. The bit might wear out faster, too. Check out the Bosch Dry Diamond Core Bit—it’s tough enough for dry work.

Related: What is Core Drilling? Dry vs. Wet Core Bits & Best Tools for Concrete

How to Drill into Asphalt (Step-by-Step Guide)

Drilling into asphalt demands a careful approach to ensure safety, accuracy, and efficiency, so you can continue with your project without setbacks . Let’s walk you through the process to avoid slip-ups and deliver solid results.

Step 1: Gather Your Tools & Safety Gear

Start by rounding up everything you need. You’ll want a core drill machine—something handheld like the Bosch GDB 2500 for shallow holes, or a stand-mounted option like the Hilti DD 150-U for deeper, wider cuts. 

Pair it with the right bit: carbide-tipped for smaller holes under 2 inches, or a diamond-tipped core bit like the BLUEROCK 4-Inch Asphalt Core Bit for tougher jobs.

If you’re going with wet drilling for testing , connect a water supply system—think Husqvarna Water Feed System—to keep the bit cool and dust down. For dry drilling, hook up a vacuum dust extractor like the DeWalt DWV012 to keep the air clear and the site safe.

Safety comes first, so gear up with the essentials: impact-resistant goggles to block flying debris, heavy-duty gloves for grip and vibration protection, a dust mask or respirator to avoid breathing asphalt dust, and hearing protection because drills get loud. 

A quick tip: stash a fire extinguisher nearby at all times, especially if you’re using electric tools outdoors near anything flammable.

Step 2: Mark the Drilling Spot & Prepare the Surface

Getting the spot right is key to avoiding trouble later. Grab some bright spray paint or chalk and mark where you’ll drill. If you’re on a road, double-check utility maps or use ground-penetrating radar (GPR) to steer clear of hidden pipes or cables. Sweep away loose gravel, dirt, or debris so the drill sits steady.

In busy areas, set up safety cones and signs to keep people out of harm’s way. If the asphalt’s uneven, smooth it out around the drill spot with a grinder—it’ll keep the machine stable. For jobs with multiple holes, mark all your spots upfront to save time and keep things consistent.

Step 3: Start Drilling (Wet vs. Dry Techniques)

Wet Drilling Method

First, hook up the water supply by attaching a hose to the drill’s inlet—something like the Hilti DD-BI Asphalt Core Bit works great with 1–2 liters per minute. Kick things off at a low 300–500 RPM to carve a guide groove, which stops the bit from slipping. 

Once that groove’s in place, crank it up to 800–1,200 RPM for standard asphalt. Press down steadily, but don’t muscle it—let the drill’s weight do the work. For example, if you’re cutting a 6-inch hole for a drainage pipe, hold a 45-degree angle until you’re all the way through.

Dry Drilling Method

Attach a vacuum system like the DeWalt Dust Extractor to catch the dust. Drill in short bursts—20–30 seconds at 1,000 RPM, then pause for 10 seconds to let things cool. 

Check the bit’s heat between cycles; if it’s too hot to touch, give it a longer break. Here’s a handy trick: If you hit concrete under the asphalt (like on roads), switch to a diamond-tipped bit mid-drill—it’ll chew through both layers without a hitch.

Step 4: Remove the Asphalt Core & Clean the Hole

When you’ve drilled through, ease the bit out slowly to avoid jams. To free the core, wiggle the bit gently, and if it’s stubborn, nudge it loose with a pry bar or chisel. 

Vacuum out the loose debris to prep the hole for whatever’s next—installs or testing. If the edges are rough, smooth them with an angle grinder and a diamond cup wheel for a clean finish.

For back-to-back holes, let the bit cool 5–10 minutes between rounds. Store carbide drill bits in a dry case to dodge rust, and rinse diamond bits with water after wet drilling to wash off asphalt gunk. A smart move: Label your cores with the spot and date for testing down the line.

Final Checks & Best Practices

Take a moment to check your work. Measure the hole’s depth and width to make sure it’s spot-on for the job. Jot down a few notes—drill speed, bit type, any snags—to reference next time. Wrap up by cleaning the drill and bits right away; it keeps them in top shape for the long haul.

Follow these steps to minimize asphalt cracking, reduce tool wear, and complete projects efficiently. For large-scale jobs, consider renting a stand-mounted core drill with a vacuum base—it offers unmatched stability and precision for demanding asphalt drilling tasks and high-quality products.

Common Mistakes & How to Avoid Them

Even the best in the business can trip up when drilling asphalt. Spotting these common mistakes—and knowing how to steer clear—keeps your project on track, saves cash, and cuts the frustration.

Mistake 1: Wearing Out Your Bit Too Soon with Concrete Drill Bits

Why It Happens: Dry drilling thick asphalt or revving the drill too fast builds up heat that dulls the bit quickly.

How to Fix It: Go for wet drilling with a diamond core bit like the Hilti DD-BI Asphalt Core Bit. Water cools it down and clears the junk. 

Stuck with dry drilling? Work in 30-second bursts and let the bit chill out between rounds.

Mistake 2: Cracking the Asphalt Around Your Hole

Why It Happens: Hammering too hard or starting at full speed can split the surface, especially on old, beat-up asphalt.

How to Fix It: Ease in at 300–500 RPM to cut a guide groove, then bump up to 800–1,200 RPM. With a stand-mounted drill, let its weight do the heavy lifting—no need to lean in. Perfect for fragile pavement.

Mistake 3: Kicking Up a Dust Cloud

Why It Happens: Dry drilling spits out fine asphalt and concrete dust that blinds you and clogs the air.

How to Fix It: Hook up a vacuum dust extractor like the DeWalt DWV012—it sucks up 95% of the mess. For indoor gigs or tight spots, wet drilling wipes out dust with water.

Mistake 4: Picking the Wrong Bit for Asphalt Over Concrete

Why It Happens: Asphalt often hides a concrete base, and regular bits, unlike an asphalt drill bit, choke when they hit it.

How to Fix It: Use a diamond-tipped bit like the BLUEROCK 4-Inch Asphalt Core Bit for more effective testing . It powers through both layers smoothly and easily—no tool swaps are needed.

Best Core Drills for Asphalt Drilling

Top-Rated Core Drill Machines for Asphalt

Hilti DD 150-U Core Drill – Best for large-scale asphalt drilling

Why It’s Great:

• Three-speed gearbox (0–1,400 RPM) for versatile cutting.
• Auto water feed and the capability to handle bits up to 6 inches.
• Vacuum base locks it steady on rough ground—perfect for highway crews.

BLUEROCK Z-1 Core Drill Machine – Best for wet & dry drilling versatility

Why It’s Great:

• Speed adjusts from 1,100–2,200 RPM for different drilling needs.
• Powered by a 15-amp motor, compatible with both diamond and carbide bits.
• Lightweight design, ideal for confined utility work spaces.

Husqvarna DM 230 Core Drill – Best for high-speed coring

Why It’s Great:

• Cranks up to 2,300 RPM for rapid drilling.
• Capable of drilling up to 10 inches deep, ideal for parking lot lines.
• Ergonomic grips provide added comfort for extended use.

Pro Tip: Pair with the Husqvarna DMS 240 Dust Management System for dust-free dry cuts.

Recommended Asphalt Drilling Accessories

Husqvarna Water Feed System – Best for wet drilling

• Pumps 1.5–2 gallons per minute to efficiently cool bits and control dust.
• Compatible with most stand drills for enhanced performance.

DeWalt Vacuum Dust Extractor – Best for dry drilling dust control

• Features a HEPA filter to capture fine asphalt dust.
• Equipped with a 12-gallon tank, reducing the need for frequent emptying.

Conclusion: Mastering Asphalt Drilling

Great asphalt drilling boils down to three things: the right gear, smart moves, and staying on top of the details. Wet drilling with diamond bits is king for deep, clean holes—especially in thick or mixed pavement, so be sure to use them correctly. For fast, shallow cuts, dry drilling with a vacuum setup gets it done safe and quick.

Gear like the Hilti DD 150-U or BLUEROCK Z-1 is worth every penny—less downtime, better results. Just as big: start slow, watch your bit’s temp, and keep the dust under control for your crew and the surface.

Ready to crush your next asphalt job? Hit up your equipment hub for pro-grade bits, drills, and extras to continue achieving successful outcomes. With the right tools and a little practice, you’ll tackle every project like a champ and wow your clients every time.

Visit Johnson Tools to shop for the best asphalt drill bits and core drills today to equip yourself for flawless performance on every project!