Patent Number: 6,305,885

Title: Hole enlargement apparatus

Abstract: A hole enlargement apparatus which uses a simple spring biased disc to center a larger hole cutter in the existing hole and a disc retention means to ensure that the disc does not fall unretrievably into the enlarged hole. The apparatus is used in conjunction with a conventional large hole cutter of the type having a toothed cylindrical cup, a hub axially secured in a bottom portion of the cup, and a pilot bit axially and removably secured through the hub and cup. The hole enlargement apparatus comprises: a guide member having a disc portion dimensioned to matingly fit within the existing hole, a rim portion connected to a rear portion of the disc portion adapted to seat on the workpiece, and a disc center guide opening dimensioned to slidingly accept a shaft the diameter of the pilot bit; a drill bit replacement shaft having a hub end portion and an opposite disc end portion; a cotter pin carried by the disc end portion of the drill replacement shaft to prevent the guide member from sliding off the disc end portion of the shaft; and, a spring to bias and maintain the disc portion in the existing hole.

Inventors: Linthicum; Leo (Colorado Springs, CO)


International Classification: B23B 51/04 (20060101); B23B 035/00 (); B23B 051/04 ()

Expiration Date: 10/23/2018