If a mushroom head develops on a chisel, swaging tool, or packing iron, what is the recommended course of action?

• A. Remove the mushroom with pliers
• B. Hammer it flat
• C. Safely grind off the mushroom and use the tool again
• D. Discard the tool

Answer: (C)

A mushroom head on a chisel, swaging tool, or packing iron is a deformation from peening the edge, which creates a rounded bulge that weakens the edge and can snag or shatter if used as-is. The best course is to safely grind off that mushroom and restore the true edge. Grinding removes the bulge, re-establishes the correct bevel, and keeps the tool working reliably, rather than weakening it further or risking a dangerous failure. While grinding, keep the tool cool, use light, steady pressure, and re-check for cracks or other damage after the mushroom is removed. If there are cracks or structural damage, the tool should be replaced; otherwise, you can resume use after a proper re-sharpening.