When drilling holes, the bit suddenly breaking through the workpiece can cause the chuck jaws to bump into the workpiece.

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When drilling holes, the bit suddenly breaking through the workpiece can cause the chuck jaws to bump into the workpiece, which leaves an ugly round scar in the surface. I found a preventive measure amid my rotary-tool accessories: a felt polishing wheel. Slip the wheel over the drill bit and you'll put a stop to errant chuck marks.
—Douglas Tapling, Reed City, Mich.