If you’ve ever walked through a machine shop floor, you’ve likely seen a radial drilling machine: that tall, adjustable arm mounted on a heavy base, spinning a drill bit with precision to cut holes in metal, wood, or plastic. For the last 12 years, I’ve been supplying radial drilling machines to job shops, aerospace fabricators, and automotive parts makers across North America, and one question I hear more often than any other is: “Can this thing tap threads?” Radial Drilling Machine
I get it. Tapping is one of the most common, high-stakes secondary operations in metalworking. Mess up a thread, and a perfectly machined component is scrap. Most shops dedicate separate tapping centers, press brakes with integrated tapping heads, or even hand taps for small runs—so why would anyone want to use a radial drilling machine for the job? For years, I avoided giving a direct answer because it’s not a yes or no question; it depends on your setup, your tolerance, and your part volume. After repairing dozens of radial machines that were used (and misused) for tapping, and helping dozens of shops adapt their drills to thread cutting, I can tell you: yes, a radial drilling machine can tap threads—if you do it right.
Let’s start with the basics. What is a radial drilling machine, and what is tapping? A radial drill’s key features are its swiveling arm, adjustable head, and heavy-duty column, which let you move the spindle horizontally over large workpieces without repositioning the part. Its spindle has variable speed control, forward/reverse feed, and a quill that moves up and down under power. Tapping, by contrast, is cutting internal threads by driving a tap into a pre-drilled hole, then reversing the tap to back it out. The critical difference between drilling and tapping is “chase thread ratio”—or how the forward feed of the tool matches the pitch of the tap. A 1/4-20 tap, for example, needs the tool to move forward exactly 0.05 inches per full rotation to cut clean threads. If the feed is too fast, the tap breaks; too slow, and threads get stripped.
Most standard radial drilling machines are built to handle drilling, not synchronized tapping. That’s where the confusion starts. A lot of shops I work with try to rig a tap on a standard drill chuck, flip the spindle to reverse when they hit depth, and hope for the best. This almost never works—unless you’re tapping a very large, coarse-pitch thread on a soft material like aluminum. Let’s say you’re tapping a 1-inch-8 thread (coarse pitch, 0.125 inches per revolution) on a thick steel plate. A standard radial drill with a 0.05 inch per revolution feed (common for small drilling jobs) would be way too slow for that tap, leading to a broken tool in the hole and scrap. I had a shop in Detroit call me three years ago because they broke 12 M12 taps in a single shift, trying to tap engine mounts on an old manual radial drill. They were using a M12 x 1.75 tap, but their drill’s feed was calibrated for drilling, so it only moved 0.08 inches per revolution—far too slow, and the tap ripped the threads out before they even finished driving it in.
So why do some shops swear by radial drilling machines for tapping? It comes down to upgrading the machine’s spindle controls. Early on, I saw a job shop in Cleveland adapt a 1998 manual radial drill we sold them in 2005. They added a tapping attachment with a floating chuck—also called a tap collet chuck, which gives the tap a little “give” so it can move slightly axially if the spindle’s feed is off by a hair. More recently, we started selling radial drills with synchronized tapping capabilities, which eliminates that manual calibration entirely. Synchronized tapping uses the machine’s CNC (we offer both manual and CNC models) to link the spindle’s rotation exactly to the spindle’s feed, so the feed per revolution matches the tap’s pitch automatically. No more guessing, no more broken taps.
But before you rush to upgrade your radial drill for tapping, you need to ask yourself three questions: What are you tapping? What’s your tolerance? What’s your volume? If you’re running small, low-volume jobs (like prototype parts or 10 to 50 pieces a year), a standard radial drill with a floating tap chuck might work for coarse-pitch threads. If you’re tapping high-volume parts (like 1,000+ pieces a month) or tight-tolerance threads (like aerospace-grade M6 x 1.0 threads with a ±0.002 inch depth requirement), you’ll need a CNC radial drilling machine with synchronized tapping. I’ll give you a real example: Last year, we worked with a aerospace parts maker in Texas that was outsourcing all their tapping operations because their old manual radial drill couldn’t handle the M8 x 1.25 threads on wing bulkheads. They bought our mid-range CNC radial drill with a 5-axis spindle, and now they tap 200 bulkheads a week in-house, cutting their tapping costs by 65%. That’s not a small win—for shops that work with large, heavy parts (like wind turbine components or construction equipment frames), moving tapping to a radial drill means you don’t have to load the part into a separate tapping center, saving hours of setup time.
There are also myths I hear all the time about radial drills and tapping. The first is that radial drills are too imprecise for fine threads. That was true 15 years ago, when most radial drills had manual dials with 0.01 inch feed increments. Today’s CNC radial drills have feed resolution down to 0.0001 inches, which is precise enough for even medical-grade tapping (think orthopedic implants, which require threads with no dimensional error). Another myth is that tapping on a radial drill causes too much vibration. Again, that’s true for old, worn-out machines. All the radial drills we sell have heavy cast-iron bases and columns that absorb 90% of spindle vibration, so even when you’re tapping at 150 RPM on a 2-inch tap, there’s no chatter in the thread.
That said, there are limits. If you’re tapping threads smaller than M3 (0.118 inches) or pitches finer than 0.5 mm, a radial drill is probably not the right tool. Small taps like that snap easily if the feed is off, and most radial drills don’t have the spindle speed control to run small taps at the high RPM they need (small taps need 500+ RPM, while coarse taps can run at 50 to 100 RPM). For small, fine threads, a dedicated tapping center or a mill with integrated tapping is still better. Also, if you’re tapping blind holes (holes that don’t go all the way through the part), you need to set the spindle’s depth stop very carefully. Too deep, and you’ll ram the tap into the bottom of the hole; too shallow, and the thread won’t be full. CNC radial drills let you set depth stops to within 0.001 inches, so blind hole tapping is totally manageable.
I’ve been in this industry long enough to know that shops hate buying new equipment unless it solves a clear problem. A lot of my customers ask: “Why would I modify my radial drill to tap when I already have a tapping machine?” The answer is flexibility. If you’re a job shop that runs a mix of drilling, tapping, and milling jobs, a single CNC radial drill can do all three, cutting your floor space and equipment costs. I had a customer in Chicago who used to have three separate machines: a radial drill, a vertical mill, and a tapping center. After buying our 2022 CNC radial drill, they sold two of the three machines, saving over $100,000 in annual equipment leases and setup time. They now drill, mill, and tap all their customer parts on one machine, which means faster turnaround for their jobs.
Another big benefit of tapping on a radial drilling machine is accessibility. For large parts—like a 10-foot wind turbine blade root flange, or a 15-foot construction equipment frame—you can’t move the part easily between machines. A radial drill’s arm can swing 180 degrees along the column, letting you reach every hole on the part without repositioning it. If you had to move that 15,000-pound frame to a separate tapping center, you’d need a crane, extra labor, and a lot of downtime. Tapping on a radial drill eliminates all that. We recently worked with a wind energy component maker in Iowa that was moving their 12-foot flanges to a tapping center 45 minutes away, costing them $2,000 per day in transport and setup. They bought a large-capacity CNC radial drill from us, and now they tap all flanges on-site, cutting their lead times by 80%.
So how do you get started tapping on a radial drilling machine? Here’s the step-by-step guide I give all new customers: First, match your tap to your setup. For coarse threads (pitch ≥1.5 mm) and low volume (<50 pieces), use a floating tap collet chuck on your manual or CNC radial drill. For fine threads (pitch <1.5 mm) and high volume (>50 pieces), upgrade to a CNC radial drill with synchronized tapping. Second, calibrate the feed. If you have a manual drill, check the feed rate by drilling a test hole, measuring its depth at 10 spindle rotations, and adjusting the feed until it matches the tap’s pitch. If you have a CNC drill, you can input the tap’s pitch directly into the machine’s control, and it will calibrate automatically. Third, use cutting oil. Tapping generates a lot of heat, which can cause the tap to expand and snap. For steel parts, use a heavy-duty tapping oil; for aluminum or brass, use a lighter oil. Finally, test on scrap parts first. Always run a test tap on a piece of scrap the same material and thickness as your production part, to check for stripped threads or broken taps before you run your first production part.
I’ve spent 12 years refining these processes, and I’ve seen firsthand how tapping on a radial drill can transform a shop’s efficiency. But I also want to be honest: it’s not for every shop. If you only run small, fine threads in low volume, a radial drill won’t save you money. But if you work with large, heavy parts, run a mix of operations, or want to cut the cost of separate tapping equipment, a radial drilling machine is a viable, cost-effective solution.
If you’re curious about adapting your existing radial drill for tapping, or if you want to learn more about our CNC radial drilling machines with synchronized tapping capabilities, get in touch with our team. We can help you assess your current operations, recommend the right setup, and provide training to make sure your tapping runs smoothly. No pressure, just honest advice for your shop’s needs.
5 Axis CNC Milling Machine References:
- “Machinery’s Handbook: Tapping and Thread Cutting Processes”, Industrial Press Inc.
- Radial Drilling Machine Operation and Maintenance Manual, American Machine Tool Distributors Association.
- “CNC Tapping Synchronization: Precision in Thread Cutting”, Journal of Manufacturing Processes, 2021.
Shandong TaoFong CNC Machine Tool Co., Ltd.
Shandong TaoFong CNC Machine Tool Co., Ltd. is one of the most professional radial drilling machine manufacturers and suppliers in China, featured by quality products and good price. Please rest assured to buy durable radial drilling machine for sale here from our factory. Customized orders are welcome.
Address: No.3189, East of Longquan Road and North of Kangzhuang Road, South sha he, Tengzhou City, Zaozhuang City, Shandong Province
E-mail: tony@tafocnc.com
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