Let me get right to the meat of this question. Under table 6.1 in D1.1 it is stated that the size of a fillet weld... may be less than the specified nominal size without correction etc, etc, by said amount for 10% of the weld length... Since weld size is equal to leg length this would mean you may reduce the leg size. not the throat. i have a non-degreed "welding engineer" claiming that it is ok to reduce the throat. curious as to your opinions.  I emailed AWS and got this response...

Michael,

•  In regards to your question on whether the size of a fillet weld refers to the leg or the throat of the weld, the following guidance is offered (clauses and figures are per D1.1:2008) :
o   2.2.5.2 Fillet Welds and Welds in Skewed T-Joints. The following shall be provided on the shop drawings: For fillet welds between parts with surfaces meeting at an angle between 80° and 100°, shop drawings shall show the fillet weld leg size, For welds between parts with surfaces meeting at an angle less than 80° or greater than 100°, the shop drawings shall show the detailed arrangement of welds and required leg size to account for effects of joint geometry and, where appropriate, the Z-loss reduction for the process to be used and the angle
o   From Figure 5.4 Acceptable and Unacceptable Weld Profiles size is consistently shown as the leg length

o   Annex K Terms and Definitions that provide a definition for fillet weld size. For equal leg fillet welds, the leg lengths of the largest isosceles right triangle that can be inscribed within the fillet weld cross section. For unequal leg fillet welds, the leg lengths of the largest right triangle that can be inscribed within the fillet weld cross section.

All of this seems to indicate that fillet weld size in D1.1 is governed by leg length.

Respectfully,

thanks