I believe D1.1 allows and undefill on fillet welds of 1/16" of an inch.

Charles

According to AWS D1.1 the amount of undersizing allowed on a weld depends on the size of the weld but the length of the undersized part of the weld cannot exceed 10% of the weld length. Basically if you have a 5/16" weld 10" long, a total of 1" of that weld is allowed to be 3/16".
You can undersized 10% of a 3/16" or less weld by a 1/16" or less and a 1/4" weld by 3/32" or less. Anything weld over 5/16" is allowed to be undersized by 1/8" or less as long as the undersized part of the weld does not exceed 10% of the total length of the weld.

I believe you've gotten an answer already for D1.1, however; that answer does not apply to all codes. I suggest providing more information for a relevant answer.

in the "Certification manual for welding inspectors" 4th edition chapter 2 , question 14,,,,it says that fillet welds can be measured using a tolerance of -1/32 of an inch......."Where" is this info at........i'm aware if what QCCWI explained , but this is different.......????????????????

thats "minus " 1/32 of an inch.........

Assuming AWS D1.1 is the applicable code, technically speaking, anything under the specified size is a small weld, except as allowed.  QCCWI quoted what that underrun allowance is.  So even a thousandth of an inch under, or less, can be considered as undersized.
From a practical standpoint, it is difficult to measure a thousandth of an inch on a fillet weld.  Generally, if that level of precision is needed, then the weld should be machined to the final size.

What many inspectors will do to evaluate a fillet size is:  if the weld doesn't quite make the leg and/or throat size, check it with the next smaller gauge.  If the weld is larger than that size, the weld is accepted.  If it is at or does not quite make the smaller size, the underrun allowance is evaluated.

So in a roundabout way, you could say that minus 1/32" is a practical tolerance that many people go by.  Just remember that the code does not actually give out that allowance; any amount undersize is still undersized.  If a weld is for a critical application, it is best to check the requirements first.