In CGA pamphlet C-6.1, Standards for Visual Inspection of High Pressure Aluminum Compressed Gas Cylinders, it states in section 4.2 that cuts or digs are acceptable to the following limits:

1. Unknown wall thickness, maximum dig = .031" deep

2. Known wall thickness, maximum ding = 15% of minimum design wall thickness.
a) A ding in the sidewall could be: .471" (min side wall) x .15% = .071" deep
b) A ding in the center of the base (the thinnest part of the base) could be: .735 (min base) x .15% = .110" deep
c) A ding in the radius and footring at the bottom of the cylinder could be: .110" deep + .04" footring height) = * .150" deep * This ding cannot extend up into the sidewall.

3. The length of the ding must be less than 6.0".