"We don't believe it!" – that's how experienced machinists reacted to their first encounter with a machine tool that had produced nine bores per part with only 0.000020 in. (0.5 µm) variation, all day long, with essentially no operator attention. That's 2.21 Cpk process capability. It's transformative technology in a shop like Waltz Brothers Inc., a precision grinding and machining operation in Wheeling, Ill., where these parts – flight-critical hydraulic pumps – are produced by the hundreds every year.

So, it did not surprise president Larry Waltz that his machine operator complained no one at the shop believed the results, achieved by a new Sunnen SV-1015 honing system on its first run of production parts.

Waltz knows it's hard to hit this tolerance window honing one bore per part, to say nothing of nine bores, as the shop had been doing with a standard machine. With nine opportunities to make a micron-sized mistake on an expensive workpiece, it takes great skill and many time-consuming machine/measure iterations to make these parts on a standard machine.

The new hone not only produces perfect bores, it also records its final air gaging measurements to track with each serialized part. "When I showed this new machine to a customer for whom we'd been making these parts, they were so impressed they wanted us to commit to a blanket order for all their parts for the next five years," Waltz said. "In that instant, we validated our painstaking decision to adopt this technology."

One critical detail about the Sunnen machine is a patented, new ‘smart tooling’ technology that servocontrols the force on a honing machine's tool feed system. This and other machine automation capabilities, such as robotic part indexing and in-process air gaging, have created a new reality at Waltz, a company that looks at machining through the eyes of a precision grinding shop.

"We're a second-generation grinding business started by my father and uncles in 1939," explained Waltz. "Our focus is close-tolerance precision parts requiring many operations that typically conclude with grinding, honing, or lapping, so we added chip cutting to better control the processes upstream from grinding.

“Most machine shops don't process blanks in a way that facilitates good grinding, honing or lapping results,” he continued. “For example, if a part is machined between centers, most shops will not be too concerned about variation in the centers, which will affect how consistently the part locates in a grinding fixture. We want to control these factors -- straightness, hardness, stock allowance, etc. If grinding is only a side business to a shop's chip cutting, they won't look at things the way we do."