How should non-current carrying metal parts of portable electric tools be grounded when connected to a power source?

Grounding non-current carrying metal parts of portable electric tools is essential for ensuring safety and preventing electrical shock. When these tools are connected to a power source, a three-wire cord is the appropriate method for grounding. This type of cord includes a live wire, a neutral wire, and a dedicated ground wire, which is crucial for providing a safe path for electrical faults.

The third wire, the ground wire, is connected to the metal parts of the tool that do not carry current during normal operation. If a fault occurs—such as a short circuit—this grounding mechanism directs any stray electricity safely into the ground. This reduces the risk of electric shock to the user, as the grounding system helps to protect against electrical failures.

Using a two-wire cord does not provide a grounding option, which can leave the user vulnerable to electric shock if a fault occurs. Grounding with a rubber mat or a grounding rod does not effectively protect the tool's user during regular operation of portable tools as they do not offer an integrated, instantaneous path for electrical faults through the equipment itself. Therefore, utilizing a three-wire cord is the standard practice for safely grounding metal parts of portable electric tools.