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I am lost for understanding what to pick for tapping a hole that is 1/2 inch 20 tpi. My set seems to serve bother system. But then it seems to be only metric. The second tap from the right seems to be the right one 1/2 NF20. But how could a tap serve both metric and whitworth system. I guess that it is M14x 2.0 pitch.

How to read it correctly?
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