| 摘要 |
<p>A drill for forming an undercut in the base part of a hole drilled into masonry comprises a drive shaft (20) and a cutter assembly (2) coupled to a distal end of the drive shaft. The cutter assembly comprises a support structure (4) and an array of cutters (10) mounted on the support structure for pivotal movement between a retracted position in which the cutter assembly can move along the preformed hole into the base of the hole and a radially-expanded position in which the cutters form a generally conical undercut in the base of the hole upon rotation of the drive shaft with the conical undercut widening in cross section in a direction towards the outer end of the hole.</p> |
