That is how my original idea looked like, but what you have just draw can't be done with conventional method of machinning, ok maybe on high speed cnc mill with super fine bit, but that would take ages to mill, and be incredibly expensive, edm should be able to do this, but again making a tool for edm is done by conventional method so that would again be very expensive.
In my design I compromise to be able to make it on my machine, first block MWBC mk2 you can see in my thread I used 2mm bit and then milled out 16 straight radial chanells of course like cathar said that way you mill out central part of the block. So in my current final design MWBC mk3 I milled out 8 4mm radial chanels and in the center left a cone with 8 round chanell on the surface.
Now I'm thinking how to use thin cutting blades of smaller radius, to cut radial chanells, but still in the center small cone would be left out which I don't believe it's a bad thing at all.
myv65 , some finite rounding of end mill bit edge would definetly exist, but if you magnify close enough what is perfect edge, it doesn't exist because the molecules and atoms are round
End millied edge is sharp enough so that it won't have any good effect on flow rate.
edit: I add another pic. of Mk3 block how it looked:
http://forums.procooling.com/vbb/sho...6024#post46024