Production Machining

AUG 2013

Production Machining - Your access to the precision machining industrial buyer.

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TECH BRIEFS Tips for Improved Holemaking By Jack Lynch C utting tool manufacturers face a constant challenge when raising performance levels of their products, including the important intermediate area of holemaking. But depending on their type, drills can vary substantially in their capabilities. Tey have established application areas according to hole requirements, practical limits to tooling and tool development. A few drill types dominate holemaking, a machining process made up of sub-areas that are evolving along with changing drill capabilities. capability of 5× the diameter. Tis type of drill can also be reconditioned, with a complex geometry requiring fveaxis grinding. Exchangeable-tip drills are a more recent development, shown to provide various benefts that have helped to establish a position in the market for this type of drill. In general, they provide tolerances in a range that falls between those of solid carbide drills and indexable insert drills, with some overlap. Tese drills ofer benefts over brazed drills. Frontrunners Indexable insert drills provide unbeatable production economy, with high machining productivity for bolt-type holes as well as some thread-tapping holes. Drill-depth capability is 5× the diameter. Solid carbide twist drills are ground and have the capability of making accurate holes with a high surface fnish. However, they represent a relatively expensive tool even when reconditioning is considered. Brazed carbide-tipped drills are ground and represent an intermediate diameter and tolerance area. Diameters typically range from 0.39 to 1.18 inch, with a depth 26 PRODUCTION MACHINING :: AUGUST 2013 Holemaking Advancements Te intermediate area of holemaking has signifcant room for improvement. Holes of this type are found on a number of diferent components and materials formed by solid carbide and indexable insert drills. Tey can be deep holes, more precise fabrication holes, tubesheet holes in heat exchangers, fne holes made by reaming, and close-tolerance holes made for tapping. Te technology of exchangeable tip drills can be limited both by its capabilities and the practical nature of the operation in terms of minimum and maximum sizes for acceptable tip design,

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