More Than a "Stopgap": Intermediate Sleeves Ensure Safe Clamping and Precision

They appear to be unimposing - but they are located at a decisive interface in the chain of the metal cutting process. Between toolholder and workpiece, the intermediate sleeves influence reliability and precision of the clamping operation. The thin-walled, mostly slotted precision sleeves cover the difference between the clamping diameter of the toolholder, and the workpiece which has to be clamped. Functioning like reduction inserts, they multiply the fields of application of the toolholders or arbors, compensate tolerances, and ensure safe and gentle clamping of gear wheels. The newest sleeve design can do even more. Intermediate sleeves with nozzle effect extend the tool service life and increase the volume machining.
From the technical point of view, these flexible accessories have highly sophisticated features. They evenly transfer the clamping force via their whole wall, radial to the toolholder onto the workpiece, or onto the tool shank. Thereby the complete clamping force acts on them. Eroded slots in the wall provide the necessary flexibility to the intermediate sleeve, and leave enough space for the coolant supply. Since they are an additional interface, they have a great influence on the achievable run-out and repeat accuracy. In case of intermediate sleeves for precision toolholders, it is lower than 0.003 mm.
Intermediate sleeves are mainly used in toolholding systems for covering the clamping diameters. Various clamping diameters can be reliably clamped in one mounting, which increases the user‘s flexibility, and in turn, saves the user money. They can be used in hydraulic expansion toolholders, but also for tool mountings with polygonal clamping technology, or in toolholders with elastomer technology. There are two considerable restrictions: due to the thermal effects, intermediate sleeves cannot be used in heat shrinking toolholders, whereby the flexibility of the mountings is significantly reduced. However in collet chucks, mechanical collets are used. They also cover various clamping diameters and thus replace the intermediate sleeves. But their run-out accuracy is not efficient for most of the precision applications, which differentiates from toolholders where intermediate sleeves are used. 


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