Typically, if an external threaded part is cut too small, it ends up being rejected or scrapped. Because API RSC threads are tapered, moving the shoulder back makes the “under-sized” thread essentially “larger”.
When cutting/inspecting an external API pin rotary shouldered connection, it is not necessary to scrap the part if the thread is measured and found to be undersized. If the stand-off is too small ( less than 0.620″) the torque shoulder can be faced back by a corresponding amount (on the Z axis) to bring the stand-off back into tolerance.
For example, API pins have a standoff of 0.625″ with a tolerance range of 0.620″ -0.635″. Therefore if the pin was cut too small and the stand-off reads 0.615″, the shoulder can be faced back 0.005″ to meet the minimum acceptable standoff of 0.620″ or farther. Gagemaker ST-7001 gages help you control this process by quantifying the standoff in a repeatable fashion.