Lenox Laser makes some really nifty orifice fittings. I recently ordered some of the 1/4" tube fittings because I wanted some orifices for my igniter that are smaller than the 0.014" available as flare jets.
The 1/8" tubes got me thinking about another project and so I was looking at buying some of the smaller orifice fittings and modifying them for my own use. The problem was they really only have up to 3" lengths without added cost. And even at $30 they seemed a bit pricey to buy and carve up. A search of the web found no easy source for the blanks they make so I tried my hand at making one myself.
I first tried to make a mandrel using a 1/8" ball end mill. That didn't work particularly well. I had a ball bearing spinning tool for the lathe left over from another project, so I tried it.
It worked very well. The tube in the picture below is my very first attempt with the technique. I was anticipating having to spot weld the end but it is water tight to 60 psi which should be good enough for what I have in mind.