ASTM A6-08 Plate Tolerance Question

[fabengr]

In Table 1 of ASTM A6-08 there are five (5) notes. Note 4 reads "For thicnkesses measured at any location other than that specified in Note 3, the permitted variations over specified thickness shall be 1 3/4 times the amount in theis table, rounded to the nearest 0.01 in." I read this as allowing me to multiply the table's values by 1.75 if I am measuring the thickness at a location different that that identified in Note 3. (Note 3 tells you to measure the thickness 3/8 to 3/4 inches from the longitudinal edge. This seems excessive to me. A 75% increase in the allowable thickness tolerance. Am I reading this note correctly?

 

[JStephen]

That sounds reasonable to me. For one thing, the rolling process is going to inherently have a tendency to roll thicker in the middle that has to be counteracted. For another, this probably dates from long ago when measurements were by micrometer, which meant there was not necessarily a reasonable way to measure the thickness out in the middle of the plate. And lastly, in most applications, plate being overly thick isn't really objectionable, unless you have to pay for that extra weight. If it was more critical, tolerances might be tighter.