High-Speed Finishing of Hard Gear Teeth with cBN-Tipped Hob
Yoji Umezaki*, Yasutsune Ariura*, Toshio Suzuki**, and Ryohei Ishimaru***
*Faculty of Engineering, Kyushu University
744 Motooka, Nishi-Ku, Fukuoka 819-0395, Japan
**Department of Mechanical Engineering, Faculty of Engineering, Fukuoka University
8-19-1 Nanakuma, Jonan-Ku, Fukuoka 814-0180, Japan
***Dept. of Mechanical Engineering, Kurume National Collage of Technology
1-1-1 Komorino, Kurume, Fukuoka 830-8555, Japan
The hobbing finish of hard gear teeth such as case-hardened gears is anticipated for practical use in high efficiency production. We studied wear and finished surface properties in cutting tests using a cubic boron nitride (cBN) hob cutter in high-speed cutting at 900 m/min of case-hardened steel. The cBN content in tip ingredients is related to wear, and tips high in cBN content are superior in wear resistance. The high thermal conductivity of cBN tips helps transfer cutting temperature heat to chips, melting and adhering them to the relief surface. Flaking may occur on the cutting edge but new chipping does not occur although chipping may exist after grinding. Finished surface roughness is influenced by horning on the cutting edge. Round horning leads to a smooth surface. High-speed finishing with cBN-tipped hobs is analyzed in view of cBN tip grinding and finished surface properties, in addition to wear properties.
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