What precaution should be followed when using a chisel that has a mushroomed head?

When dealing with a chisel that has a mushroomed head, the most prudent course of action is to remove the ragged edges by grinding. This process helps restore the chisel's edge and overall effectiveness, allowing for safe and efficient use. A mushroomed head can create safety hazards, as the deformed metal can chip or break during use, potentially causing injury.

By grinding away the mushroomed portion, you ensure that the chisel functions as intended, maintaining its sharpness and structural integrity. This preventative measure helps avoid further damage to the tool and enhances your safety during operations. Metal tools should always be kept in good condition to ensure they operate properly and safely.

While immediately replacing the chisel, oiling it, or using it only for soft materials might seem like feasible options, they don't address the core issue of the mushroomed head affecting the tool's performance and safety. Simply oiling the chisel would not resolve the deformity, and using it on softer materials does not eliminate the risks associated with a damaged tool. Therefore, grinding the edges is the safest and most effective solution.