I do not have 27 tpi gage, I expect it to use a compression nut like all the rest but at this point I just do not know. It fits an 8mm bolt gage perfect, am I heading in the wrong direction? Perhaps NPS? The Luke primer has no O rings. Go to True Value aviation supply and get some 3/32 teflon valve packing. Be sure the little washer on the shaft is not worn to the point it falls into the primer. Wrap about 4 turns of packing around the shaft between the washer and lock nut. Lube with EZ turn and you should be good to go.