Hole Saw Enlarging Centering Cone
This cone stops a hole saw from wandering when you enlarge an existing 14–50 mm hole. You put the cone on a scrap board under the workpiece and let the old hole settle onto its 30° slope, which centres the hole. The arbor pilot bit then runs into a 6.7 mm guide bore that fits 1/4 in and 6 mm pilot bits. The cone is 56 mm across and 13.4 mm tall, has sight rings at 20, 30 and 40 mm hole diameters, and has three counterbored #6 screw holes for fixing it to the scrap board.
tool hole-saw drilling centering