Any reason that once you finished the rest of the CNC work, you could not take the part to a rotary table to cut the groove?
That is a great idea - To be honest, I didn't really know what a rotary table was until just a few days ago. I don't have a lathe, but with that tool it would be doing exactly what
Wreck™Wreck was suggesting, except I could use my mill, with the same endmill I've been using. It would take all the drama resulting from trying to make a boring bar out of 1.6mm diameter HSS.
Now that the rotary table is in high consideration,
what would be the most accurate method of getting my groove cut exactly where I want it on the mold surface? I did some reading online and found that some people mill a shallow hole in the center of the desired diameter, put a pointed tool in the collet, and lower the spindle down. This would effectively center of the circle in line with the spindle, the spindle being zeroed on the DRO with the center of the rotary table. From there, it could be offset with the radius of the circle.
That centering method would work for boring the OD of a hole, but not for this groove (the post in the center would have a small pit in it's surface, resulting as a bump in the mold).
