For aerospace and medical parts, Martin recommends the B21*SGL series drill. These and other industries rely extensively on stainless steel and heat-resistant superalloys (HRSA), metals that create extreme heat and high amounts of mechanical force. The result is a built-up edge (BUE), chipping of the drill corners and margin lands, and chip binding, ultimately leading to unpredictable drill breakage. Kennametal has addressed such failure modes, Martin says, with special point gashing and a positive rake angle at the cutting edge to reduce cutting forces. A polished cutting edge and flute help to further reduce these forces and promote chip evacuation, as does the drill’s hard, wear-resistant KCSM15 coating.
“The B21*SGL drill is available in a broad range of inch and metric sizes, and hole depths up to 8xD,” Martin says.
Hard, but Tough
Brandon Hull agrees with the need for shops to periodically reevaluate their drilling tools.
The vice president of product management and business development at Guhring ticks off an equally impressive attribute list, adding that modern drills are also much tougher than those of even a decade ago.
Read more: Meet Guhring’s RT100XF: A High-Performance Carbide Drill Developed for Tough Metals
“Setting aside any geometry considerations, the carbide drills made today are simply much better than they once were,” he says. “For example, our RT100XF high-performance drill is now available in a new grade, K40XF, which retains the hardness of carbide but is tough enough for interrupted cuts and similarly abusive applications.”
It also makes these drills more suitable for less-than-rigid or manual machining environments, applications that often have shops reaching for high-speed steel tools, due to the steel’s greater toughness and flexibility. Granted, Hull suggests dropping feed rates by roughly 50 percent when breaking into a cross-hole or starting on an angle with solid carbide drills, yet this is a small price to pay given that carbide runs four to six times faster than HSS, especially when coated with one of the many multilayer coatings now offered by most cutting tool manufacturers.
One of these is Guhring’s nano-FIREX, which Hull explains is an upgrade to the company’s decades-old FIREX coating, one that relies on “additional but thinner” layers to extend tool life and increase operating parameters. Of course, there’s also geometry to consider. The makers of high-performance carbide drills pay special attention to details that, at first glance, might seem insignificant. Hull points to features such as micro-honing of the cutting edges for greater strength, and polishing of the flutes for improved chip evacuation, and don’t forget that many carbide drills are equipped with double margins, an attribute that increases stability as well as hole quality.
There are also several material-specific options, starting with the RT100VA, a coated, coolant-fed drill in 3xD and 5xD lengths, and designed specifically for stainless steel.
“We also have the RT100HF, which is similar to the RT100XF but better suited for nickel alloys and titaniums, as well as our RT100AL for aluminum,” he says.
“Lastly, there’s the RT100U for steels, probably the most general-purpose of our drill lineup but still falling into the high-performance category,” he adds. “That’s the one I often recommend to job shops that are drilling a wide variety of materials in lower production volumes.”
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I look forward to any new innovations in the machining world. Having more effective tooling is always a step in the right direction. I use solid carbide drills on my manual mill everyday and they hold up great to the case hardened steel I have to drill through!! Great work.
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