John Swope’s tip in FHB #240 (“Corralling a Wandering Hole Saw“) tells how he wrapped the pilot bit of his hole saw with masking tape so that it wouldn’t wander in a small-diameter hole in a door. It’s a good idea for that specific situation. But what if the existing hole is too large to bulk up the pilot bit with tape? In that case, I use a hole saw of my desired diameter to cut a hole in a plywood scrap. This becomes my guide block. As shown in the drawing at left, I clamp it to the workpiece where I need the larger hole. Now I don’t need to worry about the pilot bit; the guide block keeps the hole saw from wandering.
J. Kaye, Phenix, VA