How do I grind a tool bit for this?

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Investigator

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I need some help. Im trying to cut into the face of a part. How do I grind a tool bit for this job:
20180920_195111[1].jpg
The red arrow indicates the face I need to cut. Basically, I need to end up with this:
rear cap 1_zpsttaa3qiu.jpg

the outer ring is to be a tight slip fit into a tube. The 'trench' if you will is about .5" wide and about .75" deep.

I'm thinking of leaving the end of a 3/16 tool bit with just relief for a straight plunge cut, and giving some back rake. something like this:
download (1).jpg

I'm looking for ideas and suggestions
 
Look up Joe Piecznski's video on trepanning a groove in a face of a part. He does a good job of explaining the tool geometry needed, and why. That should get you headed in the right direction. The tool you show may work if you have enough outside clearance so it doesn't rub the outside of the groove. Too flat in the bottom may chatter, at least something to watch for. Interesting part.
 
Just get two tools like you pictured, one right and one left. Mark out your rough dimensions and with the tool pictured feed in and towards the center at the same time. Next use the opposite tool and feed in and out till you get it roughed out. To finish, the groove has to be wider than twice the tool width. use the one pictured to turn the inside OD and face out till the tool almost rubs the outer inside. Use the opposite tool, touch off for the bottom and bore the outer inside and face down till it meets your previous face.
 
Have a heavy enough lathe to make that cut. The method above, alternating, will obviate the need for a heavy machine. But will be a time-consuming task.
 
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I recently needed to do the same thing, except it was in aluminum. I started with a brazed carbide parting tool and ground off most of the support so that I could get a face groove about 0.25" deep (until it started to bind). Then I could go in with a small boring bar - lathe in forward to get the larger ID and the lathe in reverse with the tool on the other side of the pin to get the small OD. Then back with the modified parting tool I could get another ~0.25" deeper. The result was exactly what I wanted. There would likely have been faster ways to get'er done, but once I got at it, it went pretty quick (aluminum is forgiving).

Why the brazed carbide parting tool? I have had about 4 in my tool box for the past 10+ years, I never use them for parting (preferring carbide insert or HSS blade) and the face plunge tool was quick and easy to make that way. Grinding a HSS tool blank would have worked fine too - in my case it was simply more grinding.
 
Make a tool with left and right cutting edges and relief in the middle like a v. Just clearance. Plunge and move left to right. Make sure the width of the tool is small enough so when go from left to right or right to left you can cleanup the pass on the other side.
 
GL said:
Look up Joe Piecznski's video on trepanning a groove in a face of a part. He does a good job of explaining the tool geometry needed, and why. That should get you headed in the right direction. The tool you show may work if you have enough outside clearance so it doesn't rub the outside of the groove. Too flat in the bottom may chatter, at least something to watch for. Interesting part.
Click to expand...
I wanted to suggest that too. Brilliant bloke Joe Pi
 
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