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The sweeping, arcing motion of tool against work in five-axis applications has always mesmerized me. However, I found the promotional video above to be particularly immersing, and not just for the complex, harmonious interplay of the axes driving the table and spindle motion. Get past that, and you'll notice those cutters taking particularly large slices of the worm gear component on each and every pass.

Instinct and experience would likely drive many manufacturers to employ a ballnose tool for many of these operations. That's despite the fact that the tools in the video engage more of the work to enable larger stepovers, and, by extension, reduced machining time and smooth surface finish. Yet, even among those who are familiar with "barrel cutters," a common name for tools with exceptionally large cutting edge radii, going with ballnose wouldn't necessarily be all about comfort and familiarity. Historically, these types of tools have been manufactured as specials, and few CAM packages have offered support.

That's according to Open Mind Technologies, a CAM developer that has offered support for these geometries for more than a decade now. Recently, however, its efforts have gone beyond just support. The latest version of the company's HyperMill software offers dedicated finishing strategies for a conical barrel cutter that tapers at the tip for improved access and other benefits, a geometry that differentiates it from traditional designs. What's more, that tool is produced as a standard, along with three other geometries, by cutting tool manufacturer Emuge-Franken, which partnered with Open Mind on the development of all four and produced the video above. This brief article details the development, features and advantages of these tools, which have been dubbed "circle-segment end mills" and are available in North America as part of Emuge Corp.’s Top-Cut line.