192 students has been welding for 20 years. Most of our welders learn in the in the fall with some starting the year before. Only a few have welded for years. Early on it was .125 or thicker. About 8 years ago I showed some students how to check for penetration by breaking welds with a hammer.
With the increase skill due to their critiquing their own welds we now weld .062 and thicker. 192 also rivets and has found that 3/16 and 1/4 rivets work rather nice and have few problems.