Another side to this discussion is the higher level quality philosophy you want to run your business by. By inspecting and sorting the final output or dependent variables of your process, you are incurring unnecessary costs. It has also been said that 100% inspection is not 100% effective. It is possible that by running to this philosophy you will have high internal scrap costs and also still allow unacceptable parts to get to your customer.
By checking the independent process variables throughout the process and controlling them, your end result will be improved. To do this, each process step must have a control plan and you need to measure and control features important to each downstream customer. This requires capable measurement equipment. Calibration to verify accuracy as well as R&R, linearity, and stability should be done on measuring equipment.
This is fundamentally explained by "six sigma" with the y=f(x) relationship, where the output

is a function of independant variables (x).