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Holemaking Coolant-through inserts on Iscar’s ChamDrill Jetdrills cool workpiece while enabling efficient chip evacuation.

that you bore or drill is a round hole. It’s very difficult togenerate a tapered hole in a machining center. There’sonly some very specialized pieces of equipment that cando it, and with your run-of-the-mill CNC machining cen- ter, it’s not possible.” Quality threaded holes depend heavily on accuratelydrilled holes. They’re especially important in aerospaceapplications that demand threads adhering to stringentquality levels, and where rework or scrap of expensive aerospace workpieces represents a costly or unacceptablescenario.“The drilling operation is certainly one of the criticalaspects to a good tapping operation, with the prepara-tion of the minor diameter, especially when you get into the exotic materials, such as the titanium alloys and theInconels that are common to aerospace,” notes MarkHatch, manager, thread milling, at Emuge Corp.(Northborough, MA). “One of the scenarios that they’vefaced with regard in particular to tapping is that it’s usu- ally the last operation performed, so the user has invest-ed a lot in manufacturing that part. And then when we get to threading, if we have a failure at that point thatresults in either rework requirements or even potentially a very high risk of scrap, the user can lose all the money spent on the part.”With Emuge’s new generation of solid carbide Aerothreadmills, aerospace manufacturers can produce internal “J” series threads in aerospace materials including Inconel 718, titanium, and 15-5 PH/17-4 stainless steels, Hatchnotes, meeting the requirements for the minor diametermandated under the MIL-S-8879 specification. The Emuge threadmill, which can machine all materials up to RC58,feature select micrograin carbide engineered with multiplespiral flutes and employing a profile-corrected micro-geom-etry. The tool’s design incorporates an axial internalcoolant supply for efficient chip removal, and a PVD TiCN coating for improved edge wear and thermal stability.“When we get into aerospace, their challenge is the dif-ficulty of the materials that they machine,” Hatch notes.“There’s a lot of squeezing characteristics that are presentin these types of materials that cause tool breakage prob- lems and very low tool life.”Aerospace manufacturers including Boeing, Pratt &Whitney, Rolls-Royce, and General Electric are continual- ly reducing their in-house chip capabilities and using more subcontractors, Hatch adds. “The challenges that subcon- tractors face is that their margins are always squeezedwith regard to how much they can get per piece,” he says,“and typically the quality standards that they’re held toare even higher than what the company would hold itselfto.” The J-series threads are safety-critical threads often found in aircraft engines, airframes, and space vehicles,Hatch notes. “They’re used especially heavily in enginecomponents, where you have components that must resistfatigue, and experience a lot of heat stress.”

WANT MORE INFORMATION? For more information on the holemaking equip-ment mentioned in this article, circle the numberson the reader service card. CompanyCircle Bilz Tool Co. Inc. 360 Carboloy Inc. 361 Emuge Corp. 362 Kennametal Inc. 363 Iscar Metals Inc. 364 Komet of America Inc. 365 KPT Kaiser Precision Tooling Inc. 366 Sandvik Coromant 367
March 2003? www.sme.org/ manufacturingengineering

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