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Machine designers are sometimes confronted with high contact pressure conditions which generate plastic deformation. However there is no clear design method for such severe condition. We investigate the contact condition in the high contact pressure by using a ball-on-glass disc type test. According to the test results, the following conclusions were obtained. 1) The ratio of calculating contact pressure and the hardness in consideration of working hardness, the number of the ratio is settled about 0.4 for any loading condition. 2) In the condition of high contact pressure generating plastic deformation, the contact pressure converges with constant value according to the work hardening behavior of material.

Micro-Traction-Drive is made by modified angular contact ball bearings. It is developed for the purpose of transmitting high torque with small drive size. Structure of Micro-Traction-Drive is as follows: The traction force is generated by the thrust preload between inner race and outer race. The retainer connected to the output shaft transmits the driving torque. The retainer is made from copper alloy. The test-runs of Micro-Traction-Drive (outer ring diameter 42mm) have been carried out as tandem stage type (reduction ratio 7.3). The test results demonstrate that Micro-Traction-Drive has been successfully operated at 20,000rpm. Furthermore, material of retainer has been examined. Effect of retainer material on efficiency of Micro-Traction-Drive was revealed.