Well, life has a funny way of messing up machining plans. But today, got a chance to work on it again.
Took the pre-drilled 3/8" rod and turned it to diameter, at 6.95mm and 7.86mm. Used a piece of MoMax HSS, that I had found in my father's desk (about a year ago) to turn the 1144. Very satisfying to use one of his tools. I think the MoMax dates from when he worked in the Radiation Laboratory, around and after WWII. He was a technician there, and was a jack of all trades, working on synchrotrons, magnetrons, and all sorts of interesting projects. He had to learn on the fly, learning how to fabricate and use vaccum furnaces, make magnetrons and klystrons, and whatever was asked of him. Anyways, back to machining.
Used a 3/8" collet, and a 7mm collet to hold the probe. First I turned the long 24mm section to just under 7mm. Then I changed collets to 7mm and flipped the piece and turned the remaining 3/8 stock to 7.86mm. Well, almost 7.86, I got 7.862mm, not wishing to muff it, I'm leaving that alone! For the 7.86 section, I took 2 0.25mm passes, a 0.15mm pass, a 0.1mm pass, an 0.05mm pass and a 0.038 pass. I was checking for deflection, but fortunately, there was very little. Love that HSS.
Now I'm wondering if now's the time to cross drill it, as I haven't put in the rest of the features. The hole is only 1mm in diameter, and I have to drill it on the mill. Think that will be the next step. I don't know how straight the previously drilled 1.5mm hole is, hope I'll intercept it, because that's how the air gets to the airgun!
Oh, I already have a spare probe. This work is for me to learn how to make things outside of my comfort zone. It's been a learning experience in design and in implementation. Slowly building skills.
Anyways, this is the print so far. Really ought to have another page, the dimensions are a bit cluttered for me. And incomplete. I try to fix them as I find them - usually when trying to machine it! Oh, I didn't dimension that. Stop. Go fix that, make new print, back to the shop...