I'll try to make this clear as possible it wasn't all that complicated.
First thing is I new is that I wanted to scrape those slots with a tool like on a
an old shaper machine because I would have the room to do it that way. And I
could use the compound on the lathe to give me a horizontal movement across the
face of the part.
One problem was indexing the part so it could be divided into six equal parts or
slots. I also have a milling machine with rotary table so I took the chuck off the lathe and put it on the rotary table and marked the chuck in the mill at every 60 degrees. Put the chuck back on the lathe and put a mark on the lathe to indicate
against the chuck. Now I could turn the chuck by hand to each position to be cut.
The next issue was I needed a tool to cut the slots, that was the hard part.
After a couple of tries what I ended up with was a 3/16 round high speed tool
First step was to grind a flat spot on the tool steel about .100" back and .050 deep. That became the facing edge or the cutting edge, angle is not critical, straight is just fine. This i did on the bench grinder.
Next I put the tool in the lathe and set the cuttin edge down facing the floor.
Then I used a home made lathe grinder from a small drywall router could have used my Dremel but for some reason I forgot I had it. It the Dremel has a mount made also to fit the lathe. Will show pics if you want. Then I cut about half way
through with the grinder about .050 deep.
Then i turned the tool cutting edge up facing the ceiling and at an angle that gave me a slight taper toward the back of the cutting edge for clearance, so basically your grinding a long taper rectangle, the flat that was ground is the front and widest part of the rectangle and also the cutting edge. Hope that's clear. Grind
untill you reach .010" wide at the face edge.
I had to make a holder for the cutting tool to fit my lathe.
Then shim it to center it to the lathe.
Now with the part in the lathe, that too takes a special part because the back of the injector is larger than the front. Set the lathe speed around 450 just to give it enough resistance to not move when milling your part, and set the chuck at the mark on the lathe and a mark on the chuck.
Move your tool so the cutting edge is against the outside edge of the part, set a dial indicator at zero, if you don't have a dial indicator for your carriage now is a good time to make one. Move your tool away and move it to the center of the part,
you can indicate it here too on the .400" dia. that you will be cutting through.
Back to the center, move your tool in .001" and back out your cross feed through the part. You should see the metal curl in front of the cutting edge, I used a magnifing glass to see. Move the tool back to the center and take another .001" cut. Repeat untill you have cut down .010" , move the chuck to the next position and repeat the process again.
Use cutting oil and feed slow and smooth. My tool was still sharp after finishing the job.
Any questions feel free to ask.