What is the permitted length of undercut for an arc spot weld of 1 inch diameter when welding sheet steel?

In the context of arc spot welding, the permissible length of undercut is critical to ensure the integrity and strength of the weld. According to industry standards, particularly when welding materials such as sheet steel, the maximum allowable undercut should be defined in relation to the diameter of the weld.

For a 1-inch diameter arc spot weld, the specifications typically allow for the undercut length to be a fraction of the weld diameter. The correct choice indicates a maximum length of undercut that aligns with the standards usually adopted in welding practices.

In this case, 0.39 inch is within acceptable limits for undercut on a weld of this diameter, allowing for the necessary strength of the weld while also considering potential stress concentrations that excessive undercut might introduce.

This option is consistent with widely accepted welding codes, which aim to balance weld quality with manufacturability and structural requirements. Understanding these specifications is crucial for welders aiming to achieve certification and ensure that their welds meet safety and performance standards.