Minimizing Polishing: General Industry Coverage

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END USER: Tech NH Inc., (603) 424-4404, www.technh.com. CHALLENGE: Reduce polishing time when producing hardened steel molds. SOLUTION: Long-reach, small-diameter endmills for hard milling. SOLUTION PROVIDERS: Harvey Tool Co. LLC, (800) 645-5609, www.harveytool.com; Industrial Tool Supply, (888) 200-8887, www.itslowell.com.

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Courtesy of Tech NH

Tech NH applies small-diameter, long-reach endmills from Harvey Tool, such as this 0.047 “-dia., 2-flute, AlTiN-coated one, to hard mill many mold features that were previously EDMed.

Tech NH Inc., Merrimack, N.H., provides molding services including engineering and manufacturing molds and injection molding parts. The shop performs prototype and custom work, as well as production runs from a few thousand to several million pieces.

The molds Tech NH produces often are complex and require fine surface finishes. Achieving those finishes typically required up to 50 hours of polishing time after EDMing. To mill graphite EDM electrodes, Wayne Burgett, toolroom manager, had been applying PVD-amorphous-diamond-coated miniature endmills from Harvey Tool Co. LLC, Rowley, Mass. Seeking to maximize tool life in the abrasive material, Burgett wondered whether Harvey Tool could coat the tools with CVD diamond, estimating that the thicker coating could extend tool life eight to 10 times.

Tim Stimson, sales representative for distributor Industrial Tool Supply, Lowell, Mass., brought Harvey Tool representatives to Tech NH.

In addition to confirming the availability of CVD-coated tools for machining graphite, the Harvey Tool personnel “wanted to look at my other processes,” Burgett said. “They just happened to come in when we were producing a twin- cavity mold made of 48- to 53-HRC 420 stainless. The required finish was almost a mirror.”

Harvey Tool was able to provide small-diameter, long-reach endmills that enabled Tech NH to hard mill many mold features that were previously EDMed. Hard milling imparted a finer surface finish than EDMing, enabling Tech NH to achieve the mirror-like finish with only 5 to 6 hours of polishing instead of the 40 to 50 hours necessary when EDMing was more extensive. (Tech NH still EDMs some small features that a milling tool can’t access.) In addition, Burgett said, “We are saving time on electrode design, graphite milling, EDMing and programming.”