Its time for horn tooting. I just passed my D9 welding certification test, the only one in the class. I am certified to weld 10 (3/16 inch) to 18 gauge(3/64 inch) metal. This my friend is no small feat. I needed to have a consistent weld both in height and width. I also needed to have the weld penetrate to the backside of the metal through the whole run. Even if there was a pin prick sized spot that wasn't penetrated but otherwise perfect that would still be a fail. he instructor even took a magnifying glass to the welds looking for imperfections. Didn't find any!
