If the needle ends up redundant I'll have it! Need one for a Hurrican!

Steve,

For slight knurling, without the fancies of a strong lathe and knurling tool, I've found a pair of coarse hand files does a passable job.

Clamp one file flat across its width in a vise with the surface definitely above the vise jaws. Roll the part between that surface and the other coarse file. Unless you slide the piece on one or the other file's cutting faces, you will 'upset' the surface slightly, somewhat like forming a 'rolled thread.'

Works fine on most kinds of brass I've tried it on. Doesn't 'grow' the diameter much, but it may not need much to grab the spraybar hole in the Webra's casting.

(This also works well to put some 'tooth' on a brass outer surface when epoxying-in a threaded tube or pivot bearing. You can use 60-grit paper instead of hand files, and get more of a 'dotted', or even 'diamond' hatching pattern.)

On the other hand, where are the Kap-Pak Universal NVA's from way back when??? Would be just the thing...

Ah, managed to get hold of a spray bar from a Taifun Hobby which I bought as more or less a project for restoration from a guy here in Sweden.
Problem solved... sort of...

The little Hobby engine was in better shape than expected although someone turned the compression plunge upside down.
Corrected the problem and put a proper compression screw in place of the much too short one I found in the engine.
It runs super, actually.
Now I find myself without the complete NVA for THAT engine 
Life's a struggle, a pleasant struggle though.