| 摘要 |
Cutting teeth around the lower edge of an inverted cup-like cutter cut a circular kerf resulting in a circular slug being cut from the material being worked on. The proximal end of a retainer is fixed centrally of the cutter and the distal end projects beyond the plane of the teeth so the resilient tab means on the distal end can be deflected inwardly towards the longitudinal axis of the retainer as the retainer passes through a pilot hole in the material. The tabs engage the underside of the material when the retainer has been passed through the pilot hole and enable removal of the slug through the hole cut by the cutter.
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