What is a typical recommended gap for patch-fitting a body panel to allow for MIG welding and filler, and why?

• A. 1/2 inch gap to allow more filler.
• B. No gap at all.
• C. 3/8 inch gap to maintain alignment.
• D. 1/16 to 1/8 inch gap to allow for filler bead and pinholes while maintaining alignment.

Answer: (D)

Leaving a very small seam gap when patch-fitting for MIG welding is essential. A narrow gap around 1/16 to 1/8 inch gives enough room for the weld bead to bridge the joint and for filler metal to accumulate, helping the patch sit flush with the surrounding panel after finishing. It also helps maintain alignment and control heat input to minimize distortion, while reducing the chance of defects like pinholes by allowing proper fusion and gas escape. Gaps that are too large would require excess filler, raise distortion risk, and make alignment harder to keep; no gap prevents proper bead formation and fusion.