| 摘要 |
A tool and a method for drilling holes having an increased cross-sectional area in a region remote from an exposed surface of the support structure in which the holes are to be drilled include mounting a drill bit having cutting edges at one end of a resiliently-deflectable, elongated force-transmitting spring, and angularly displacing an other end of the elongated force-transmitting spring so as to resiliently deflect said one end thereof into a plurality of positions in each of which the cutting edges of the drill bit are brought into engagement with the inner circumferential wall of the hole being drilled so as to form undercut surfaces in said region. |
