If you’re in the market for DTH (down-the-hole) bits, chances are you’ve Googled “how fast do these things actually drill” more than once—same here, I get it. Let me cut through the jargon I see every day on industry forums and customer questions, since I’ve been a DTH bit supplier for 7 years now, working with quarry crews, water well drillers, and construction teams across North America and parts of Latin America. No stuffy textbooks, just real talk about drilling speeds, what makes them tick, and how my team’s bits fit into that puzzle. DTH Bit
First off, let’s nail down what “drilling speed” actually means here—because it’s not just a single number you can plug into a spreadsheet and call it a day. Most drillers refer to two key metrics: penetration rate (that’s linear speed, like feet drilled per hour) and rotational speed (RPM, which ties directly to how hard the bit works). People ask me all the time, “What’s the average speed?” and I usually start with, “Well, it depends on what you’re drilling through, what DTH hammer you’re using, and how you’re running the machine.” Let’s break that down with real-world examples, not just lab data.
Let’s start with the rock—this is the biggest variable, hands down. Soft to medium rock, like limestone, sandstone, or weathered granite? That’s where you see the highest speeds. Last year, a water well customer in Texas was drilling through layered limestone and soft shale with a 6-inch DTH hammer and one of our standard carbide-taper bits, and he hit over 80 feet per hour during his best runs. Another quarry guy in Arizona drilling through hard limestone for road aggregate was averaging 45 to 55 feet per hour with the same bit size, same setup. That’s a big gap, but it makes sense—quarry rock is way denser and has less natural fracturing than a well’s soft, layered formations.
Now hard rock—think unweathered granite, basalt, or quartzite. That’s where speeds drop fast, and it’s not uncommon to see 10 to 25 feet per hour, sometimes even lower if the rock is super abrasive. I had a customer in Minnesota drilling for bedrock water, and he hit a patch of solid granite that only let him get 12 feet per hour with a 8-inch bit. The mistake he was making? He was running the hammer at too low an air pressure, so the bit wasn’t striking hard enough to break through the hard rock. That’s another thing I see all the time: new drillers undersize their air compressor or don’t adjust pressure for the rock, and then blame the bit for slow speeds.
Wait, let’s talk about DTH hammers too—because the bit doesn’t work alone. A small 4-inch hammer (used for residential water wells or small excavation holes) will never drill as fast as a 12-inch heavy-duty hammer used for mining or large foundation work. I supplier bits for all sizes, and a 4-inch bit on a compact drill rig might average 20 to 35 feet per hour in soft rock, while a 12-inch bit on a mining rig can hit 100+ feet per hour in the same soft formation, just because the hammer’s impact energy is way higher. That’s why it’s useless to compare a residential driller’s speed to a mining crew’s—they’re using totally different gear.
Another big factor: bit design. Not all DTH bits are made equal, and that’s where my team’s work comes in. We test every bit before it leaves the shop, but we also adjust designs based on what our customers are actually drilling through. For example, our standard bullet-tooth bits are great for medium rock, but if someone’s drilling through highly abrasive granite, we recommend our carbide-button bits with reinforced steel bodies that don’t wear down as fast. A customer in Quebec was switching from a cheap imported bullet-tooth bit that wore out in 100 feet of granite and only averaged 15 feet per hour, to our heavy-duty carbide-button bits, and his speed jumped to 22 feet per hour—plus he replaced the bit half as often, so his total downtime was way lower. That’s a win, but it’s not just about “faster drilling”—it’s about speed per dollar, right?
Let’s get into the numbers that actually matter for real work, not lab tests. Most of our customers send us data, and here’s the breakdown we see consistently, after 7 years of tracking:
- Soft rock (shale, soft limestone, weathered sandstone): 50–120 feet per hour
- Medium rock (hard limestone, granite with some weathering, compact sandstone): 25–60 feet per hour
- Hard/abrasive rock (solid granite, basalt, quartzite): 8–25 feet per hour
That’s a range, I know, but that’s the real range, not the 150 feet per hour you might see in a lab with perfect conditions and a brand-new drill rig running nonstop. Also, don’t forget about RPM and air pressure—you can have all the right bit and rock, but if you’re running your hammer at 80 PSI when it needs 150 PSI, your speed will be half of what it should be. I had a driller in Colorado who was complaining his bits were slow for months, until he realized his compressor was leaking air—once he fixed that, his speed went up 30% overnight. Air leaks are the #1 thing that kills DTH performance, and it’s so easy to miss.
Wait, what about surface vs. underground drilling? That’s another variable I don’t see talked about enough. Underground, you have limited ventilation, sometimes smaller rigs, and often rock that’s been fractured from mining, so speeds can be a bit higher or lower than surface drilling. A copper mine in Utah we work with drills underground with 10-inch bits, averaging 35 to 45 feet per hour in medium hard rock, which is actually a bit faster than their surface drilling setup because the rock is already fractured from previous blasts. It’s all about context.
Now, let’s address the myth that a “faster drilling bit is always better.” I see so many drillers obsessing over maximum speed, but that’s not the only thing. If a bit is drilling 10 feet per hour faster but wears out in half the time, you’re actually spending more money overall. For example, a cheap bit that costs $200 and lasts 50 feet at 20 feet per hour is $4 per foot. Our premium bit that costs $500 and lasts 200 feet at 25 feet per hour is $2.50 per foot—way cheaper, and you get more done without replacing bits every other day. That’s the value we push with our customers, not just “speed speed speed.”
I also want to talk about what affects bit life, because that ties into speed too. If you’re drilling too fast for your setup, the bit’s buttons or teeth will wear down quickly, and you’ll have to pull it out of the hole early, which costs time. We work with drillers to match the right bit to their rock, their rig, and their needs—whether they need maximum speed for a short job, or maximum durability for a long project. Last year, a construction company was doing 100 foundation holes in Florida’s soft limestone, and they were using a standard bit that worked, but we suggested a bit with a wider face that displaced rock faster, and their speed went from 70 feet per hour to 95 feet per hour, and they finished the job 2 days ahead of schedule. That’s the kind of stuff I love hearing about, because it’s not just about selling a bit—it’s about solving a problem.
Wait, let’s get back to the original question: “What is the DTH bit’s drilling speed?” The short answer is, it depends on a whole bunch of factors, but the average real-world speed for most jobs is between 10 and 100 feet per hour, with most jobs falling in the 20 to 60 feet per hour range. But if you want a specific number, you have to tell me what rock you’re drilling, what size hammer you’re using, what compressor PSI you’re running, and how big your bit is. That’s why we never give a one-size-fits-all number—we ask our customers those questions first, then recommend the right bit to get their desired speed.
I’ve been in this long enough to know that a lot of DTH bit suppliers just throw out generic numbers to sound impressive, but that’s not helpful. If you’re drilling through solid granite, 100 feet per hour is impossible, no matter what bit you buy. But if you’re drilling through soft shale, 20 feet per hour is way slower than it should be. The key is matching the bit to the conditions.
For example, last month we had a customer from Oklahoma who was drilling water wells through mixed sandstone and limestone, and he was using a bit from a different supplier that only averaged 35 feet per hour. He switched to our medium-duty carbide bits, adjusted his air pressure from 120 PSI to 150 PSI, and his speed jumped to 55 feet per hour. That’s a 57% increase, all because we matched the bit to his rock and helped him adjust his setup. It’s not magic, it’s just knowing how DTH bits work.
I think the biggest mistake new drillers make is thinking the bit is the only variable. I always tell them: the hammer, the compressor, air pressure, air volume, rock type, operator technique—all of that matters. The bit is a key part, but it’s not the whole story. That’s why my team spends so much time helping customers troubleshoot their drilling setup, not just selling a bit and moving on. If your speed is slow, 9 times out of 10 it’s not the bit—it’s a leaky compressor, wrong pressure, or even a dull drill bit on the rig itself.
Now, if you’re a driller, a quarry owner, or a construction manager who’s tired of guessing about DTH bit speeds, or you’re looking to upgrade your setup to get faster, more consistent drilling, reach out. We don’t do one-size-fits-all advice—we’ll ask you about your project, your rock, your rig, and give you a real breakdown of what speed you can expect, and which of our bits will get you there without breaking the bank. No sales pitch, no gimmicks, just real experience from guys who’ve been in the field and behind the desk for years.
Drill Rod References
- Atlas Copco. (2021). DTH Drilling Performance: Factors Impacting Penetration Rates. Rock Drilling Tools Division.
- American Rock Drilling Association. (2022). Field Guide to DTH Bit Selection and Drilling Efficiency. ARDA Publication 2022-03.
- Sandvik Mining and Rock Technology. (2020). Down-the-Hole Drilling: Optimal Speed and Cost per Meter. Technical Brief TB-127.
Super Rock Machinery Equipment (Qingdao) Co., Ltd.
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