SCOTT DEAN MILLS
Pilots at Saddlehorn Rd, Phoenix, AZ

4749315, Jun 7, 1988

Feb 2, 1987

7/010184

Scott D. Mills - Phoenix AZ

B23B 5104

408209

A tool is provided for drilling a hole in a construction material precisely concentric to a nearly inaccessible reference aperture situated opposite the side of the construction material from which the hole must be cut. A typical application is in cutting a sprinkler head receiving hole concentric with the open end of a downwardly directed drop of a sprinkler distribution system. The tool includes an elongated rod which carries a sliding guide member constrained between a stop positioned at one end of the rod and a compression spring urging the guide member toward the stop. Intermediate the length of the rod, there is provided a hole saw retaining shoulder against which a conventional hole saw of the desired diameter cut to receive a sprinkler head may be affixed with its teeth directed toward the rod first end. In use of the tool, the second end of the rod is secured into the chuck of a drill, and the guide member is inserted through a small, rough access hole and into the open end of the drop to correctly position the tool assembly. The operator may then push the drill upwardly to force the guide member against the compression spring and thereby address the construction material with the teeth of the hole saw which cuts through the construction material to obtain the correctly dimensioned and aligned hole to receive the sprinkler head.