Mopar Muscle Association UK

Just received a new pair of tie rods for the charger, assembled the ends and sleeves. Need to install the grease nipples, they all seem a bit tight though, when they're new, do they cut their own thread on the way in?
I've obviously checked that I haven't cross threaded them, they just seem a bit tight and I don't want to damage them

TIA

There normally a NPT tappered tread

They do screw in though ?

They have a hexagonal head and what looks like a thread

Found out now, the grease nipples cut their own thread as they're wound in. The last ones I bought had the nipples already fitted when I got them