| 摘要 |
A plug ejecting hole saw includes a saw cup provided at a front annular edge wall thereof with a plurality of forward protruding angled cutting teeth, and having at a rear end thereof a circular base wall having therethrough a non-circular aperture concentric with the cup. An arbor holder removably attachable to a saw cup of a selected size includes a collar axially slidably holding therewithin a central body having a front nose piece which protrudes axially outward of the collar, the front nose piece having a transverse cross-sectional shape adapted to be inheritably received into the saw cup aperture. The nose piece has formed in longitudinal wall surfaces thereof a pair of diametrically opposed, longitudinally disposed grooves, each of which longitudinally slidably holds therewithin a locking tab member urged forward to abut a separate one of a pair of diametrically opposed, front transversely disposed web ribs formed in the nose piece axially inward of the front transverse face of the nose piece. Each longitudinal groove communicates on one longitudinal side thereof with a separate one of a pair of transversely disposed grooves blocked by a forward biased tab member. When the nose piece is inserted into a saw cup aperture and pushed axially forward, each tab member is pushed rearward in a longitudinal groove, unblocking the transverse grooves and thereby allowing the nose piece to be rotated relative to the saw cup, with peripheral edge walls of the aperture received in the transverse grooves. With sufficient relative rotation, the front tab members become axially aligned with diametrically opposed larger diameter portions of the saw cup aperture, allowing each tab to be urged forward by a front spring to a location blocking a transverse groove and thereby preventing the arbor holder from becoming disengaged from the saw cup. The arbor holder has a coaxial bore provided with left-hand internal threads for threadably receiving an arbor having left-hand external threads, has a rear shank portion adapted to be clamped in a chuck of a power drill, and has a front collet flange for clampingly receiving the shank of a pilot drill. The hole saw includes a pilot drill held in the collet flange. Rotating the saw in a clockwise sense to cut a hole in a workpiece forms a plug lodged within the saw cup, while reversing the drill with the saw cup cocked in the workpiece hole causes the arbor to threadingly advance forward from the base of the saw cup, thus causing the collet flange to advance and push the plug from the saw cup.
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