Hole saw driver-extruder and hole enlarger

A method of assembling a flanged supplementary hole saw mandrel adapted to engage the threaded bases of conventional hole saws in the pilot drill hole of the conventional mandrel of a first conventional hole saw and supporting a second smaller conventional hole saw on the supplementary mandrel concentrically in said first hole saw and spacing said smaller hole saw out from said first saw for fitting into a circular hole to stabilize said first saw around said hole for said first saw to saw a concentric enlargement of said hole, comprising the procedures of:

• inserting the shank end of a said supplementary mandrel into the open end of a first conventional hole saw mounted on a conventional hole saw mandrel, said first saw having a sawing diameter larger than the diameter of a circular hole to be enlarged;
• fitting the shank of said supplementary mandrel into the pilot drill hole of said conventional mandrel, the flange of said supplementary mandrel resting against the end of said conventional mandrel;
• tightening a set screw retained in said conventional mandrel to secure said supplementary mandrel in said pilot drill hole;
• placing a sleeve on said mandrel against said flange, the sleeve being shorter than the length of the mandrel extending out from the open end of said first saw;
• inserting the open end of said smaller saw into the open end of said first saw over said supplementary mandrel and sleeve, said smaller saw having a sawing diameter to closely fit said hole, and;
• threading the base of said smaller saw onto said supplementary mandrel against said sleeve, the said base extending out from said first saw forming a pilot to enter said hole stabilizing said first saw around said hole for sawing a concentric enlargement of said hole.

A device attachable to a conventional hole saw for driving the saw and for extruding sawed material from the saw after sawing, said saw being of that conventional type which provides a threaded mandrel mounting hole axially through its base and driving holes arranged around the mounting hole, said device comprising:

• (A) an internally right hand threaded shank having a cylindrical body, a threaded stub of smaller diameter on one end thereof adapted to engage said mounting hole in said saw base, a radial shoulder formed at the juncture of said stub and body and a flange formed on the opposite end thereof, said stub being threaded into said mounting hole with said shoulder being brought tightly against the outer base end of said saw base for said shank to form a rigid appendage to said saw;
• (B) an elongated right hand threaded mandrel adapted to engage said internally threaded shank, said mandrel having a hexagonal extension of smaller diameter on one end thereof for coupling to a drill chuck, wings formed on the opposite end thereof, said wings extending radially and a short distance toward the hexagonal end of said mandrel, the ends thereof arranged around said mandrel to conform with the arrangement of said driving holes around said mounting hole in said saw base, a hole formed axially into the winged end of said mandrel for retaining the shank of a pilot drill and a radially disposed threaded hole, intersecting said axial hole, for retaining a set screw with which to secure a drill shank when a drill is needed, said mandrel being fully threaded into said shank through the stub end thereof, the ends of said wings being brought very close to the inside face of said saw base and not aligned with said driving holes therein;
• (C) a sleeve, shorter than the length of said shank body, having pins projecting from one radial face thereof arranged to simultaneously fit through said driving holes in said saw base, said sleeve being mounted on said shank body with said pins projecting toward the stub end thereof, said sleeve being free to rotate on said body for aligning said pins with said driving holes while assembling said shank and saw and free to reciprocate thereon between said saw base and said shank flange;
• whereby, with said sleeve being moved on said shank body to rest against said saw base, the ends of said pins thereby projecting through said driving holes sufficiently far into the cup of said saw for said pins to block rotation of said wings relative to said saw, torque may be transferred from said wings through said pins to said saw during rotation of said mandrel for sawing and, with said sleeve being moved on said shank body to rest against said flange thereon, the ends of said pins thereby being withdrawn from the cup of said saw into said driving holes, and said wings thereby being free to rotate in said saw, such that said mandrel may cooperate with said shank for the winged end of said mandrel to be threaded out through said saw to extrude sawed material therefrom.