I have a question about the sizing of face seal o-ring hydraulic fittings on a 1988 John Deere 80 series loader. I know they are fine thread but are the sized by outside OD, inside OD or something else? A 13/16" open end wrench is the smallest wrench that fits over the female end theads. The male lock nut is 15/16". A 3/4" SAE bolt fits inside male end with threads just touching. Thanks for your help.