As I'm nearing getting the Corvette fully operational, I found with this new engine block that I needed a customized elbow for the oil pressure sensor. On this new (old) block, the oil pressure port is sitting on the back, top edge right by the intake manifold. With having the Holley Contender put onto the block as the manifold, I suddenly had the need to redirect the oil sensor in a different direction and away from the HEI distributor. So, I made two of them (the first one turned into a goof).
The first one I made from a block of aluminum. I ensured I had a flat and parallel surface or two to use as a marking surface.
I got them marked up.
I drilled the through-holes for the elbow first using a 7/64" drill bit, broke that off, and re-did it using a #18 drill bit. This is sufficient because the sensor only has a 0.020" hole for the pressure to make it through, so a #18 is plenty of surface area without going too large on the hole. I also used a 3/8" end mill and bandsaw to remove extra stock so I didn't have such an interrupted cut on the lathe.
Once I had the two drilled holes connected and cleaned, I chucked it up into the lathe. I centered it using the #18 drill bit to make sure I was axially in line (not a rotating part, so even if I'm off 0.005" there isn't a problem as long as I don't puncture the side or have weakness there). Then I could cut a flange and thread.
I went to install it (I never even cut the upper, female thread before this point). Turns out, it wouldn't fit. It was about a half inch too short to clear the intake manifold. [sigh]. Round two - ding! ding!
This time, I took a chunk of aluminum round bar. This was the easier way to do it, anyway. I used the lathe to drill the first hole (much longer than the first time, because I can cut stock off if needed). Then I turned it down for the shoulder, and subsequently turned down the threaded portion and installed the thread. After that, I put it in the mill and put three flat faces on there (two so I can use a wrench to get it tight enough, and one for the face that will have the intersecting hole). I did the parallel faces first, followed by the intersection next. With the last face done (and while it was still in the mill), I used a 5/16" end mill to put a hole in it, then a 3/8" part way in, followed by a short stint on a 7/16" end mill. See, this one has to be a 3/8" pipe thread, which has a taper, and the different sizes will get me close enough to use a pipe tap. I then started the pipe tap using a straight-shank center in the same 3/8" collet, and put the tap in place and began cutting.
I think this iteration is going to work just fine.
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