Precision honing of large components is a special challenge. In some cases, the bores are large enough to fit a ball or even a person, and the depth of the bores can be several meters. This is what the experts call tube honing. Gehring Technologies GmbH + Co KG, Ostfildern, Germany, has optimized this technology with the newly developed DH series of multi-strip honing tools.
With the Deephone series, Gehring offers specialized machines for honing large components. The machinable diameter range for these machines is between 37 and 600mm, even larger in special cases. Typical applications include large hydraulic and pneumatic cylinders, precision tubes in general plant engineering, extruder housings, aircraft landing legs, molds, etc. In this concept, the tool body is mounted on a drive shaft that is matched to the machine spindle. The length of the drive shaft determines the depth that can be drilled. Gehring offers four grades: 1,500mm, 3,000mm, 6,000mm and 10,000mm. The bayonet connection allows for quick tool changes. Depending on the application, honing stones up to a maximum of 300mm are available.
Because the drive shafts are connected to the machine spindle via an adapter, the DH tool series has an extremely wide range of applications.
“We are happy to help machining companies that have other, perhaps older, machines to adapt them,” said Holger Gehrung, sales manager for tools and cutting materials at Gehring. “The modular concept of our solution leaves many options open.”
Two features of the DH series are likely to be decisive for many users: The tools, including drive shafts, are optionally available with internal cooling and air metering.
Internal cooling ensures that coolant is delivered precisely to the point of machining. This means higher performance and cutting capacity with better surface quality. It also aids chip evacuation and flushes the chip/oil mixture out of the hole, significantly reducing the risk of scoring from jammed chips. The more effective internal cooling also outperforms conventional flood cooling in terms of coolant consumption, saving the user additional costs.
“We expect our new DH series tools to reduce machining times by up to 30 percent,” said Gehrung.
Air measurement is mainly used on conventional honing machines. In the field of tube honing, this type of quality assurance is rather uncommon. The advantages are obvious: air measurement allows the diameter to be checked during the process. Without air measurement, the operator must stop the process and remove the tool from the deep hole. The bore may also need to be cleaned prior to measurement, taking an enormous amount of time.
But that’s not all. Another highlight of the tools is the integrated linear feed of the honing stones. This solution reduces vibrations compared to the usual rotary feed via a rack. This not only makes the process quieter, but vibration-reduced machining also benefits workpiece quality, process reliability and tool life.
Gehring places great emphasis on flexibility when it comes to cutting tools. Depending on the application, diamond, CBN, or ceramic honing stones are available, all of which are manufactured in-house.
“We can look back on many years of experience with all types of cutting tools, and in addition to honing tools, we also equip finishing and grinding tools of all makes and designs,” said Gehrung. “We achieve maximum cutting performance and tool life thanks to the extreme hardness of the diamond and CBN cutting grains and their bonding and interaction, which we tailor precisely to the requirements.”
As a cost-effective alternative, users also have ceramic cutting tools at their disposal, which also achieve high-precision, defined surfaces. They are suitable for machining almost all materials.
Honing tools are precision products of the highest order, and the DH series is no exception. They are manufactured to the highest quality standards. This includes, for example, triple-supported support bars to achieve the best values for roundness, straightness and cylindrical shape. The tools are also designed to be very robust, so the customer can expect a long service life.
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