Trending to Turning: Hard Turning

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Holding a few tenths tolerance on a piece of 60-HRC steel was once the domain of expensive grinding equipment. Today, it’s no big deal.

A growing number of machine shops are shoving their OD grinders into the corner and replacing them with relatively inexpensive lathes. The ability to inexpensively, accurately and quickly cut hardened steel on commodity turning centers is opening doors for part manufacturers and job shops looking to reduce costs and increase throughput.

Can a Plain Jane CNC lathe really eliminate a high-precision grinder and hold a few tenths tolerance on a piece of 60-HRC steel? Blake Bailey thinks so. He’s the senior manufacturing engineer at Bronson (Mich.) Precision Products, a division of Royal Oak Industries Inc. Bailey explained how his shop turns 60- to 62-HRC 8620 steel driveline components for Harley-Davidson, as well as 4130 casehardened parts with similar hardnesses for Caterpillar. “We hold 0.0003 ” to 0.0004 ” and 16 µin. Ra all day long on 15-year-old Wasinos, no problem,” he said.

Back up the truck! Using gang-style lathes bought during the Clinton administration to turn hardened-steel motorcycle components? “When you’re only removing 0.010 ” [of material], you don’t need a super rigid machine,” Bailey said. “We use an old linear-way machine that might have cost $50,000 back in the day, compared to a grinder that cost 10 times as much.”

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