It isn't a case of the third party inspector saying the weld is 1/64 inch undersized. To do so would be a mistake a novice inspector would make. The inspector determines if the weld is conforming or it is nonconforming. Simply put; it doesn't meet the acceptance criteria of the drawing or the applicable welding standard. It is then left to the Engineer to determine if the undersized weld meets the intended service requirements of the project.
The abbreviation for inspector (other than the Authorized Inspector) is not spelled "GOD." The inspector simply reports his findings to the Engineer or the client. The work meets the requirements of the approved drawings and applicable welding standard or they are simply nonconforming.
It is interesting to note that I rarely encounter welds that are nonconforming for one reason. If the welds are running undersized, there are usually other problems as well. That is why it is important to evaluate all of the attributes and to note all nonconformances. While the undersized weld may meet the service requirements, the fact that there are unfilled craters, missing welds, unauthorized welds, arc strikes, etc. may be more of a detriment than the fact that it is undersized.
The welding inspector, whether he or she is a CWI or not, serves as the client’s eyes and ears on the project. The completeness and accuracy of the written report is what the Engineer or the client uses to judge the work being inspected. The final decision to accept or to reject work is not left to the contractor. It is the Engineer or the client that makes the final decision to accept or reject the work. That responsibility may be delegated to the inspector by the Engineer or client, but that responsibility shouldn’t be an automatic assumption.
It is all in the “Word Smithing” of the report. If the inspection report is well written, there is little chance the Engineer or the client will allow the nonconforming welds slip through.
If the concept is difficult to understand, think of it this way; You and I agree that I will pay you $100.00/hour, but when I hand you your check you discover I only paid you $99.00/hour. Somehow, even though you work with a contractor, I don't believe you would be inclined to say, "Close enough." as you skip merrily off to the bank to cash the check.
Best regards - Al