Less than 1 inch is fine, the normal milsurp is about 3/4" or a little more and the oblong commercial doors are a little LESS than 3/4" wide. I judge this by, among other things, the facts that a US military oiler will not quite fit through the commercial door and my 3/4" spur drill makes a hole that's slightly larger than the oblong commercial opening.
Regards, Joe

You can lead a man to logic but you can't make him think. NRA Life since 1976. God bless America!