Interpreting thickness tolerances of sheets acc. to ASTM A 568

Hello,
we are in doubt how to interprete thickness tolerances given in ASTM
A 568/A 568M - 03.
In TABLE 19 (Standard Thickness Tolerances for Cold-Rolled Sheet
...) there are defined "Thickness Tolerances Over, in., No Tolerance
Under", specified for several ranges of "Minimum Thickness".
Then there is a NOTE 2: "The specified thickness range captions also
apply when sheet is specified to a nominal thickness, and the
tolerances are divided equally, over and under."
Is it correct to say that the tolerance values given in the table
represent the whole tolerance range from Min to Max of thickness?
And is it correct to conclude that it is also allowed to specify a sheet
by giving its nominal ("middle") thickness with a tolerance +-X where X
is the half of the tolerance values specified in the Table 19?
Additional questions:
How thickness tolerances of sheets are usually specified in the US, by
giving the nominal thickness with a tolerance +-X or by giving the
minimum thickness with a tolerance +2 X ?
Are there standardized any "typical" (prefered) nominal sheet
thicknesses which - because of standardization - are normally available?
If so, where are they standardized?
Greatings from Germany
Joerg
Reply to
Joerg Eisentraeger
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