| 摘要 |
<p>An apparatus for drilling a large profile workpiece has a support fixable relative to the workpiece, a drill arbor centered on an axis intersecting the workpiece, a bit coaxially carried on the arbor, and a drive connected to the arbor for advancing the bit toward the workpiece either at a relatively fast advance speed or at a relatively slow boring speed. A guide element displaceable in the support parallel to the axis is secured by a compression spring to the arbor for joint movement parallel to the axis with a predetermined limited lost-motion stroke, in other words, the arbor and element can only move relative to each other through this stroke. A switch carried on the element and a switch operator carried on the arbor control axial movement of the arbor along with an abutment carried on the element and a stop on the support engageable with the abutment that define an outer position for the guide element and arbor. Thus the guide element is prevented by engagement of the abutment of the stop from moving further away from the workpiece than the outer position. A clamping device is provided on the support for arresting the guide element thereon, to that, when the guide element is prevented by engagement of the abutment on the stop from moving further away from the workpiece than the outer position. A clamping device is provided on the support for arresting the guide element thereon, to that, when the guide element is arrested on the support, the axial stroke of the arbor is determined by the switch and the operator in dependence on the lost-motion stroke.</p> |
