How to fit 1/2" BSP Radiator Air Vent

[peterpiper]

Am I missing something obvious?

Trying to fit 1/2" BSP Radiator Air Vent but there's nothing much to get hold of to tighten. Can grip last thread with pliers, but that means I can't then tighten it all the way home.
I've used ptfe string on the thread. There was a odd drop leaking (at 2.5 Bar), stopped after turning 1/8 more but not convinced.

Vent is part no. 6918 ( from 3 letter online plumbing supplier), and I'm fitting it into a 22mm compression T with BSP F end ( as opposed to a radiator).
It's for venting high point of a solar HW system, on roof - at one end of panel. So was trying to keep size to a minimum, and need all metal valve to stand the high temp.

 

[Mike Jackson]

Use item 4846

 

[Dotty]

And you're allowed to say BES.

 

[peterpiper]

B ... B ..BB .. BE . BE ..... BES. That worked!

item 4846 = 1/2" SLOTTED ALLEN KEY, TWO WAY

not sure about the slots, have a hollow end 1/2" key but the vent recess is just round.

 

[tamz]

The inside of the vent is 3/8" square. Either buy a 4846 or take the pin out and use a 3/8" ratchet drive.

Shoulda bought a 19935 or a 16383 and a 9047 :smile:

 

[peterpiper]

Photos of the 6918 fitted.

There's no sign of any flats, just the faintest sign of four corners (around 3/8" sq) having been started. Guess then it must be a machining error.
Even with pin out there's no sign of any square recess. Will try BES.