Which electrode last numbers operate on all current types?

The last numbers of the electrode classification system indicate the type of current that the electrode can operate with. Specifically, the numbers represent the polarity of the electrode, which is crucial for determining its compatibility with various welding processes.

Electrodes that end with the numbers 3, 4, and 7 are designed to operate with both alternating current (AC) and direct current (DC) in both polarities, making them versatile for different welding applications. This flexibility allows welders to use these electrodes in various scenarios and with different types of welding machines, enhancing their usability and efficiency in the field.

In contrast, electrodes with other last number classifications may be restricted to only specific types of current or polarity, limiting their application. Therefore, the classification of 3, 4, and 7 is significant as it indicates that these electrodes can perform reliably across multiple current types, catering to diverse welding needs and practices.