Why modular drills are a productive alternative

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Step over solid carbide; time to retire, high-speed steel—modular drills are a productive, cost-effective alternative

Fans of solid carbide drills (this author is one) begrudgingly admit they’re not for everyone. For starters, solid carbide is easily several times the price of high-speed steel (HSS) and cobalt, and grows downright cost prohibitive as drill diameters reach 20 mm (0.79 in.) and above. And while some carbide drills are designed to cope with intersecting holes, most are not, just as they are less forgiving of misalignment, less-than-rigid setups, and other drill destroyers as are their HSS counterparts.  

Solid carbide drills are, however, much more productive than the traditional alternatives. When combined with high-pressure, through-the-tool cutting fluid, carbide drills achieve penetration rates many times that of HSS. They also produce rounder, straighter holes, and boast significantly greater tool life to boot. 

So, what’s the answer? Break the bank for added productivity, or pinch pennies and sacrifice competitiveness and part quality? Fortunately, a new kid has come to drilling town, and it offers an attractive balance of cost-effectiveness and throughput. Meet the modular, replaceable tip drill.  

Rhymes with BAM!

David Vetrecin, Iscar Canada’s holemaking product manager, is happy to make the introduction. He says modular drills such as the company’s Sumocham line give manufacturers a best-of-both-worlds solution to a broad range of holemaking needs. “In our tools, at least, the penetration rates are equal to or higher than solid carbide, and since you only have to replace the tip, modular drills are more cost-effective and cause less downtime for tool changes.” 

Sumocham is available in lengths of 1.5 x D to 12 x D and diameters from 4 mm (0.16 in.) to 32.9 mm (1.3 in.) as standard. Vetrecin suggests that solid carbide often remains the preferred choice up to 10 mm (0.39 in.) or so, but becomes less attractive as drills grow in size and the cost of carbide tips the scales in modular’s favor. And even in those smaller holemaking applications, people recognize how fast it is to change the tip on a modular tip drill. 

Modular drills have a steel shank and body, he adds. This makes them more flexible and forgiving of misalignment but also more likely to deflect. Because of this, Iscar recommends machining a flat or drilling a pilot hole on angled surfaces greater than six degrees, or switching to a solid carbide drill. The latter might also be a better choice in hydraulic manifolds and other parts where intersecting holes tend to wreak havoc on a modular drill connection, leading to vibration, drill walk, and poor tool life. 

In most iterations, the tip either screws onto the modular drill body or attaches via a cam-style locking mechanism (as with Iscar’s Sumocham and the other brand featured in this story, Kennametal’s KenTIP FS). There’s also a proprietary pocket for highly accurate and repeatable seating. This repeatability, says Vetrecin, is one of modular drilling’s biggest advantages. It’s also why he recommends against regrinding. 

According to Kennametal, the shank on its KenTIP FS modular drill boasts large, polished flutes for hassle-free chip evacuation, enhancing tool life and performance. Image: Kennametal

Leave the grinding to us

“I don’t advise it,” he says. “Jobbing shops can sometimes get away with it because they do ten pieces here, twenty pieces there, but in a production environment, a regrind can never match the OEM’s edge prep, geometry, and coating. Even so, some customers try it despite my recommendations, only to find that tool life falls significantly or the drill fails unexpectedly, sometimes taking the pocket with it.”

Vetrecin’s other suggestion is to grip the drill with a hydraulic toolholder or hydraulic milling chuck to eliminate runout. Avoid side-lock holders at all costs, as these are known tool life killers. “I also recommend high-pressure coolant,” he says. “If you’re buying a new machine and are planning to use it for any level of holemaking, that should be at the top of your options list.”

Georg Roth might differ on the brand of modular drill he would recommend, but is in complete agreement with the application advice just given. As the marketing manager for drilling and threading tools at Kennametal, he’s pleased to announce that the company has expanded its KenTIP FS modular drilling lineup with a
general-purpose offering, the GOtip. 

“Until now, our KenTIP FS platform offered only material- and application-specific inserts,” he says. “These provide very high performance but are not very versatile—our customers in job shops and high-mix, low-volume environments were looking for a modular drill tip that would work well in a variety of materials, so we decided to leverage our GOdrill geometry for this latest product expansion, the KenTIP GTP.”

Nice margins

Like Iscar’s Vetrecin, Roth doesn’t work very hard to convert customers seeing success with solid carbide drills in the 10 mm and smaller range. Even though modular drills of all kinds are faster and easier to replace, there’s little price delta either way in these smaller sizes, and many shops prefer solid carbide for its greater rigidity. That argument loses strength as hole sizes go up. “The bigger the drill, the more economical a modular solution becomes,” he says. 

Roth points out a few additional changes to the KenTIP FS lineup. “The GOdrill itself is a margin-less design, so to increase stability in deep hole drilling, we added a pair of margin lands to the GTP insert, while an internal coolant supply supports the use of GTP inserts in challenging materials like high alloyed steel and stainless materials. We’ve also introduced a new, straight-flute body style for turning operations. Our internal testing has shown that straight flutes help increase rigidity and improve chip evacuation on non-rotating applications, or when doing manifold-type work where intersecting holes can be a problem.”

The results have been quite positive. For example, a customer drilling 26 mm (1.02 in.) diameter holes in 16MnCr5 grinder bushings (a chromium steel alloy) saw tool life increase from 1,000 pieces to 2,600 after moving to the KenTIP GTP insert. Another doubled tool life and eliminated unpredictable edge chipping in 316L stainless after switching to the new drill design, as did a shop drilling 15.5 mm (.61 in.) holes in Grade 6 titanium (Ti-5AI-2.5Sn). 

These are impressive figures, and they’re nowhere near an exception—Roth and Vetrecin each have their fair share of modular drilling success stories. But for those reading this who might look at modular tip drills as a revamped version of the spade drill, and wonder if the performance will be similar (generally poor), Roth has some final words. “People buy spade drills based on price, and while they might work well in certain applications, they provide nowhere near the performance of a well-designed modular drilling system.” SMT

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