| Popis: |
In high precision cylindrical grinding it is cutomary to support the workpiece with dead-centres. Then, the geometrical deviations of cone centres and centre holes, and their misalignments have an influence on the roundness of ground surfaces. It is known that the misalignments and geometrical deviations of centre holes do not influence the roundness of ground surfaces with the accurate and inexpensive steel balls in place of cone centres. Few reports, however, are found which are concerned with the characteristics of the ball centres. In this paper, experiments on the axial and radial stiffness were performed, at the contact parts between balls and centre holes. The obtained main results are as follows. (1) The relationships between the elastic deformations and the loads exhibit hysteresis. (2) The axial and radial contact compliances are from 0.0025 to 0.006 μm N −1 . In the ball centres, the stiffness is smaller than that of the cone centres, but the variances of stiffness are smaller than these. (3) The stiffness decreases according to the increase of the circumferential waviness of centre holes, and to the decreases of ball diameter and Young's modulus. (4) The ellipsoidal component of centre holes decreases the radial contact stiffness remarkably. |
