Workholding: Give CNC lathes an uptime makeover

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I once thought nothing of boring a new set of top jaws. Just remove half a dozen cap screws, take the old jaws out, bolt on fresh jaws, attach a spider or boring ring and crank the hand wheel until the part fits. Setups were long in the 1980s and my boss considered 2 or 3 hours of downtime each day a normal cost of business.

Today, shops might opt for a quick-change chuck. Simply twist a few screws and load a new set of top jaws. And, compared to the hours of lost production in the prehistoric days of paper tape and brazed carbide cutting tools, dropping eight to 10 grand for a quick-change chuck is a no-brainer.

But because of different workholding requirements, sometimes even a quick-change chuck can’t cut the mustard. Collet chucks, faceplates and expanding mandrels are just some of the other workholders found in most turning departments, and swapping one out means muscling 20 lbs. or more of an uncooperative steel chuck out of a CNC lathe before mounting whatever workholding device stands at bat next. This is a something that even the speediest setup man needs 20 minutes to accomplish.

“Our industry has worked extremely hard over the last 20 to 30 years to take minutes or even seconds out of cycle time. What we didn’t do is figure out how to take minutes and hours out of changeover time,” said Jeff Estes, director of Partners in THINC Technology Centers for machine tool builder Okuma America Corp., Charlotte, N.C.

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