How is the tack weld ended so it will not crack?

• A. Grind off the tack completely
• B. Stop welding immediately after starting
• C. Weld over the tack to mask it
• D. Fill each weld crater adequately to reduce cracking

Answer: (D)

Ending a tack weld correctly is about eliminating a sharp termination that can become a crack start as the weld cools and contracts. The tack holds pieces in place, and if you leave a crater at the end or stop abruptly, that abrupt geometry becomes a stress riser. By filling the crater adequately, you create a smooth, continuous transition from the tack into the full weld bead. This distributes cooling stresses more evenly and reduces the likelihood of crack formation in the heat-affected zone.

Grinding off the tack removes the feature but can leave a notch-like surface that concentrates stress. Stopping right after starting leaves a small, unjoined area that’s prone to cracking as it cools. Welding over the tack to mask it adds heat without resolving the underlying stress concentration and can make final weld quality harder to control. Filling the crater integrates the tack into the weld, minimizing abrupt changes and strengthening the joint against cracking.