Abstract
Heat generation in bearings of self-driven rotary cutting tool was investigated to improve the bearing life. Three type of tests, cutting test by rotary tool, cutting test by fixed tool and loading test modeled on cutting, were conducted to clarify the heat generation. The results showed that the heat generation in the bearing was caused by the excessive preload resulted from the thermal expansion of the tool shaft. The adoption of angular contact ball bearings preloaded by spring, which was hardly influenced by thermal expansion of shaft, was effective to the improvement of bearing life of the tool.
