| 摘要 |
<p>A circular cutter is provided for use in cutting a hole through a main pipe wall from within a branch pipe, the circular cutter including a shaft rotated about a rotational axis, a circular cutter having at an outer end cutting teeth and an inner end secured to the shaft, and at least one centering ring secured to the circular cutter external cylindrical surface and of external diameter greater than the circular cutter external cylindrical surface and less than the internal diameter of the branch pipe, the centering ring serving to centrally position the circular cutter as it is rotated within the branch pipe and also serving to provide a positive stop to axial advancement of the circular cutter after it has cut through the main pipe wall.</p> |
