| 摘要 |
PURPOSE:To selectively control the length of cut chips in accordance with a drilling condition before they are discharged from a hole, by supporting a rolling element support ring on a drill spindle in such a way that the rolling element support ring may take selectively two conditions, i.e. a stationary condition with respect to one of thrust rings and a freely rotating condition with respect to both thrust rings. CONSTITUTION:If a rolling element support ring 20 is set in a stationary condition with respect to one of thrust rings, when rolling elements 16 are fitted in recesses 27 formed in the other thrust ring, for every predetermined revolution of a drill spindle 10, the rotating element support ring 20 is axially displaced slightly in accordance with the depth of the recesses 27, and therefore, chips are cut into a predetermined length and are discharged from the drilled hole. If the rotating element support ring 20 is set in a freely rotating condition with respect to both thrust rings 15, 18, the rotating element support ring 20 are relatively rotated at a rotational speed equal to one-half of that of the spindle 10. At that time, the cycle number of displacements in the direction remote from the front end of the spindle 10, with respect to the rotational speed of the spindle, is set to be one-half of that in the above-mentioned case. |
