ground joint unions with center punched nuts

hi all...

anyone out there know about such a thing? i've never seen this fitting, and i wonder what the procedure is to create a union with a "center punched nut."

thanks in advance.

union

You install the union conventionally, and make absolutely sure it does not leak. Then you take a center punch and make an indentation where the locknut threads meet so that the union nut is locked in place. It is unnecessary if the union is tightened properly.

thanks for the reply. i thought the punching would be unnecessary if the union were fully tightened. thanks for reinforcing my belief.