by Jim Barnes
Unleashing the wiper insert’s potential in turning
Wiper inserts are well-established in turning operations, but some of their capabilities are not well-recognized. The experts interviewed for this article emphasize that these tools have wide potential applications that could enhance productivity and profitability, but that many shops seem to be unaware of them.
The wiper insert concept is based on a series of radii that make up the cutting edge. Instead of just one nose radius, a wiper edge consists of a main radius and several smaller radii. The multiple nose radii smooth out the peaks and valleys caused by conventional inserts with a “wiping” action.
“In essence, what you’re doing is extending the effective radius. By doing that, you’re producing a better finish,” explains Jan Andersson, senior global product manager, Kennametal Inc., Latrobe, PA.
Wipers first appeared about 25 years ago in milling applications and over 10 years ago in turning. There were reasons for the lag.
“In milling, the concept of the wiper is a little more obvious. In turning, there were concerns about what the wiper would do to the nose radius and whether or not that would be accepted by the market,” says Don Graham, manager of Education and Technical Services, Seco Tools Inc., Troy, MI. “Conceptually, it just is not as easy to grasp in turning as it is in milling.”
“The problem with adapting it to turning is that a straight, parallel land doesn’t work as well,” adds Dave Andrews, former product and applications specialist, turning products for Sandvik Coromant, and now regional business manager for Western Canada for the company. “It’s a little more difficult to make sure the toolholder is always 100 per cent parallel to the workpiece. Then, when it comes to profiling and so on, there are other issues with a straight, parallel land. Some engineering needed to be done.”
Capabilities
“When wipers were introduced to the metalworking industry, they were presented as a product to increase the feed rate while maintaining the finish. That is still valid, absolutely the case,” says Andersson. Shop owners can obtain the same finish at higher feeds than conventional inserts or better finishes at the same feed.
In fact, these superior finishes might even make secondary finishing operations like grinding unneccessary.
You also get good chip control at low feeds and consistent chip breaking at high feeds. “If you increase your feed rate, the chip is thicker. On the springier steels, using a wiper insert aids chip control,” explains Graham.
Negative and positive variations are available in the technology.
A positive wiper design involves less tool pressure, bringing the benefits of wipers to applications that can’t handle the extra pressure caused by the wider radius that could result in vibration and other problems.
Negative wipers support increased tool pressures, increasing cutting power on highly rigid machines. The negative angle grind pushes crater wear away from the edge, increasing tool life. SMT
Jim Barnes is a contributing editor.
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