| 摘要 |
A flanged irregular bushing is fitted through a corresponding irregular hole in the base of a conventional hole saw and supports a cylindrical shank which extends from the back of the hole saw. Either the bushing or the shank is internally threaded with right hand leading threads. A collar is free to reciprocate on the shank and has pins projecting through corresponding holes through the base of the hole saw into the cup of the saw. The distance by which the pins extend into the cup of the hole saw depends upon the location of the collar on the shank. When the collar is positioned away from the base of the hole saw the pins extend only a short distance into the cup of the saw, permitting the mandrel to be threaded deeply into the saw with the fingers on the end of the saw close to the saw base. Then when the collar is moved closer to the saw base the pins extend deeper into the cup of the saw, blocking revolution of the mandrel fingers in the saw so that when the mandrel is rotated in right hand direction from in back of the saw, torque is transmitted to the saw for sawing, and then when the collar is again moved away from the saw base the collar pins are withdrawn from contact with the mandrel fingers and the mandrel is free to be threaded out through the hole saw to extrude any residual sawed material from within the saw.
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