A better grip: Turning Performance

No matter how good the tool, it won’t cut to the satisfaction of the user if it’s not held properly. That’s why a good deal of time and money are spent on the development of toolholding technology. Not surprisingly, a major focus of these efforts is on improving toolholder grip. But toolholder manufacturers also report good progress in key areas such as better coolant delivery and faster tool changes.

Due to today’s demanding machining requirements, shops are asking for more than ever from their toolholders. That’s the word from Platinum Tooling Technologies Inc., a tool importer and distributor in Prospect Heights, Illinois. Platinum Tooling supplies accessories for a wide variety of machines. Despite the differences in their equipment, however, many customers are looking for the same things. “What we’re being asked to do is to supply products that are more accurate (to minimize runout) and can run faster,” noted Preben Hansen, owner and president of Platinum Tooling.

According to Hansen, a technology that fits the bill in both areas is shrink-fit tooling. Shrink-fit “is a very accurate way of holding an endmill in a toolholder and helps with running under high-speed imbalances,” he said. “We even sell shrink-fit collets that go into live tools. It’s a technology that can be used right across the spectrum of machining.”

When it comes to accuracy, Hansen said, shrink-fit toolholders can keep runout down at around ±0.0001″ even at the highest spindle speeds machines are capable of today. A major reason for that, he noted, is that, unlike competitive systems, shrink-fit is a one-piece toolholding solution.

Shrink-fit toolholders provide a very firm grip and can keep up with high spindle speeds. Image courtesy of Platinum Tooling

“We just quoted some tools to a customer who wanted a 16″ long toolholder,” he said. “That’s very long, but (with shrink-fit) we can make it all in one piece so it’s rigid and accurate.”

The long reach of shrink-fit tooling makes it a popular choice in the mold business, allowing manufacturers to get down into mold cavities to mill the required profiles. “The longer the reach, the more stress you get — and the easier it is to push tools off-center,” Hansen noted, adding that shrink-fit provides the firm grip necessary for accurate machining in those situations.

Another big advantage of shrink-fit is that it allows the use of very thin tools that can get into small spaces. Hansen reported that his firm produced a shrink-fit holder for a 1/8″ diameter tool, with the holder itself measuring around 1/4″ in diameter.

On the downside, Hansen pointed out that the creation of shrink-fit toolholders requires machines that range in price from around $15,000 all the way up to about $50,000. He also noted that capabilities of shrink-fit are not necessary for every toolholding application — good news for machining firms on a tight budget.

“There are a lot of small job shops that are not going to invest in this technology, and they probably don’t need to,” he said.

Rigid and Cool

For turning processes in particular, recent toolholding developments of note include the introduction of the CoroCut 2 tool system by Sandvik Coromant in Mebane, North Carolina. Developed for parting and grooving applications, CoroCut 2 features double-edged inserts produced with patented technology, as well as both a screw clamp and a rigid rail seat design that work together to hold the inserts firmly in place. The rail is a mechanical interface that prevents micro movements of inserts during machining, explained Keith Brake, the company’s turning product manager for the Americas.

Another notable upgrade offered by CoroCut 2 is the addition of internal coolant ports. Taken together, the new features “make for pretty significant improvements for parting, grooving and shallow part-off,” Brake said.

Coolant-delivery features can be found in many of the latest toolholding products, according to Alan Miller, senior manager of engineering at BIG DAISHOWA Inc. in Hoffman Estates, Illinois. The company offers chucks with coolant-delivery capabilities that supplement flood and center-through coolant systems. “We’re giving coolant that extra path to get exactly where it needs to be for improved tool life, better finishes, and all the other things that come with better coolant delivery,” Miller said.