ANSI B1.20.1 Wrench Tight Make-up Enforcement

[UCengno1]

We have struggled with proper inspection methods for NPT threads created using NC lathe. We run into conditions where the L1 gage works as required but have struggled to determine a way to verify the L3 depth. There is no appropriate NPT gage and it is the feeling of some that it is proper to apply the L3 gage to an NPT thread inspection. We fall back on para 8.3.2 of ANSI B1.20.1 where is talks specifically to achievement of the "wrench tight make-up".Has anyone put a specific inspection process in place that addresses inpection of the wrench-tight make-up of an NPT application? The case should include that the application succesfully passes the L1 gage inspection. It does not appear to be safe to assume that achievement of this is obvious to all suppliers.Thx.BCK