Oil pressure switch/sender

[dom14]

Gents I tried to fit tee piece off motor to fit oil pressure sender all was easy enough but I've got 2 male run tees 1/8 npt but neither of them are narrow enough at the mouth to even get a bite on the thread in engine block ?? Got fittings from Pirtek and one from another dealer but be buggered if they will screw in measured start up thread with vernier and it's about .4mm to big might have to try enzed or ?? Anybody have this problem or do I need a another brand of fitting as I'm stumped
Why the mongrels won't fit you can visibly see that oil switch is slightly smaller in the mouth compared to my fittings ????? Quite the conundrum and blood loss was great and the heat sheild on turbo is sharp beware.
Battleready

The oil pressure sender/oil pressure switch(same unit in my RB30 Patrol) thread pitch is 1/8NPT from memory, but it's tapered.
In other words. tip of the thread head is narrower than the other end. If you look at the sender unit fitting threaded rod, you can see it's angled. So, if you're to use a T piece on the block, that T piece has to be tapered as well as matched the pitch to 1/8NPT.
Take the sender unit to Pirtek and they will measure the taper angle and give you the correct T piece.
Without that they wouldn't know, so they would've given you the untapered T pieces.

One thing can happen is that you can accidentally end up forcing the non tapered T piece into the tapered block hole and damage the oil pressure threaded hole of the block. If that happens, there will be lot of headaches.